/*------------------------------------------------------------------------- * * xlog.c * PostgreSQL write-ahead log manager * * * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * src/backend/access/transam/xlog.c * *------------------------------------------------------------------------- */ #include "postgres.h" #include #include #include #include #include #include #include #include "access/clog.h" #include "access/commit_ts.h" #include "access/heaptoast.h" #include "access/multixact.h" #include "access/rewriteheap.h" #include "access/subtrans.h" #include "access/timeline.h" #include "access/transam.h" #include "access/twophase.h" #include "access/xact.h" #include "access/xlog_internal.h" #include "access/xloginsert.h" #include "access/xlogreader.h" #include "access/xlogutils.h" #include "catalog/catversion.h" #include "catalog/pg_control.h" #include "catalog/pg_database.h" #include "commands/tablespace.h" #include "common/controldata_utils.h" #include "miscadmin.h" #include "pg_trace.h" #include "pgstat.h" #include "port/atomics.h" #include "postmaster/bgwriter.h" #include "postmaster/startup.h" #include "postmaster/walwriter.h" #include "replication/basebackup.h" #include "replication/logical.h" #include "replication/origin.h" #include "replication/slot.h" #include "replication/snapbuild.h" #include "replication/walreceiver.h" #include "replication/walsender.h" #include "storage/bufmgr.h" #include "storage/fd.h" #include "storage/ipc.h" #include "storage/large_object.h" #include "storage/latch.h" #include "storage/pmsignal.h" #include "storage/predicate.h" #include "storage/proc.h" #include "storage/procarray.h" #include "storage/reinit.h" #include "storage/smgr.h" #include "storage/spin.h" #include "storage/sync.h" #include "utils/builtins.h" #include "utils/guc.h" #include "utils/memutils.h" #include "utils/ps_status.h" #include "utils/relmapper.h" #include "utils/snapmgr.h" #include "utils/timestamp.h" extern uint32 bootstrap_data_checksum_version; /* Unsupported old recovery command file names (relative to $PGDATA) */ #define RECOVERY_COMMAND_FILE "recovery.conf" #define RECOVERY_COMMAND_DONE "recovery.done" /* User-settable parameters */ int max_wal_size_mb = 1024; /* 1 GB */ int min_wal_size_mb = 80; /* 80 MB */ int wal_keep_segments = 0; int XLOGbuffers = -1; int XLogArchiveTimeout = 0; int XLogArchiveMode = ARCHIVE_MODE_OFF; char *XLogArchiveCommand = NULL; bool EnableHotStandby = false; bool fullPageWrites = true; bool wal_log_hints = false; bool wal_compression = false; char *wal_consistency_checking_string = NULL; bool *wal_consistency_checking = NULL; bool wal_init_zero = true; bool wal_recycle = true; bool log_checkpoints = false; int sync_method = DEFAULT_SYNC_METHOD; int wal_level = WAL_LEVEL_MINIMAL; int CommitDelay = 0; /* precommit delay in microseconds */ int CommitSiblings = 5; /* # concurrent xacts needed to sleep */ int wal_retrieve_retry_interval = 5000; #ifdef WAL_DEBUG bool XLOG_DEBUG = false; #endif int wal_segment_size = DEFAULT_XLOG_SEG_SIZE; /* * Number of WAL insertion locks to use. A higher value allows more insertions * to happen concurrently, but adds some CPU overhead to flushing the WAL, * which needs to iterate all the locks. */ #define NUM_XLOGINSERT_LOCKS 8 /* * Max distance from last checkpoint, before triggering a new xlog-based * checkpoint. */ int CheckPointSegments; /* Estimated distance between checkpoints, in bytes */ static double CheckPointDistanceEstimate = 0; static double PrevCheckPointDistance = 0; /* * GUC support */ const struct config_enum_entry sync_method_options[] = { {"fsync", SYNC_METHOD_FSYNC, false}, #ifdef HAVE_FSYNC_WRITETHROUGH {"fsync_writethrough", SYNC_METHOD_FSYNC_WRITETHROUGH, false}, #endif #ifdef HAVE_FDATASYNC {"fdatasync", SYNC_METHOD_FDATASYNC, false}, #endif #ifdef OPEN_SYNC_FLAG {"open_sync", SYNC_METHOD_OPEN, false}, #endif #ifdef OPEN_DATASYNC_FLAG {"open_datasync", SYNC_METHOD_OPEN_DSYNC, false}, #endif {NULL, 0, false} }; /* * Although only "on", "off", and "always" are documented, * we accept all the likely variants of "on" and "off". */ const struct config_enum_entry archive_mode_options[] = { {"always", ARCHIVE_MODE_ALWAYS, false}, {"on", ARCHIVE_MODE_ON, false}, {"off", ARCHIVE_MODE_OFF, false}, {"true", ARCHIVE_MODE_ON, true}, {"false", ARCHIVE_MODE_OFF, true}, {"yes", ARCHIVE_MODE_ON, true}, {"no", ARCHIVE_MODE_OFF, true}, {"1", ARCHIVE_MODE_ON, true}, {"0", ARCHIVE_MODE_OFF, true}, {NULL, 0, false} }; const struct config_enum_entry recovery_target_action_options[] = { {"pause", RECOVERY_TARGET_ACTION_PAUSE, false}, {"promote", RECOVERY_TARGET_ACTION_PROMOTE, false}, {"shutdown", RECOVERY_TARGET_ACTION_SHUTDOWN, false}, {NULL, 0, false} }; /* * Statistics for current checkpoint are collected in this global struct. * Because only the checkpointer or a stand-alone backend can perform * checkpoints, this will be unused in normal backends. */ CheckpointStatsData CheckpointStats; /* * ThisTimeLineID will be same in all backends --- it identifies current * WAL timeline for the database system. */ TimeLineID ThisTimeLineID = 0; /* * Are we doing recovery from XLOG? * * This is only ever true in the startup process; it should be read as meaning * "this process is replaying WAL records", rather than "the system is in * recovery mode". It should be examined primarily by functions that need * to act differently when called from a WAL redo function (e.g., to skip WAL * logging). To check whether the system is in recovery regardless of which * process you're running in, use RecoveryInProgress() but only after shared * memory startup and lock initialization. */ bool InRecovery = false; /* Are we in Hot Standby mode? Only valid in startup process, see xlog.h */ HotStandbyState standbyState = STANDBY_DISABLED; static XLogRecPtr LastRec; /* Local copy of WalRcv->receivedUpto */ static XLogRecPtr receivedUpto = 0; static TimeLineID receiveTLI = 0; /* * During recovery, lastFullPageWrites keeps track of full_page_writes that * the replayed WAL records indicate. It's initialized with full_page_writes * that the recovery starting checkpoint record indicates, and then updated * each time XLOG_FPW_CHANGE record is replayed. */ static bool lastFullPageWrites; /* * Local copy of SharedRecoveryInProgress variable. True actually means "not * known, need to check the shared state". */ static bool LocalRecoveryInProgress = true; /* * Local copy of SharedHotStandbyActive variable. False actually means "not * known, need to check the shared state". */ static bool LocalHotStandbyActive = false; /* * Local state for XLogInsertAllowed(): * 1: unconditionally allowed to insert XLOG * 0: unconditionally not allowed to insert XLOG * -1: must check RecoveryInProgress(); disallow until it is false * Most processes start with -1 and transition to 1 after seeing that recovery * is not in progress. But we can also force the value for special cases. * The coding in XLogInsertAllowed() depends on the first two of these states * being numerically the same as bool true and false. */ static int LocalXLogInsertAllowed = -1; /* * When ArchiveRecoveryRequested is set, archive recovery was requested, * ie. signal files were present. When InArchiveRecovery is set, we are * currently recovering using offline XLOG archives. These variables are only * valid in the startup process. * * When ArchiveRecoveryRequested is true, but InArchiveRecovery is false, we're * currently performing crash recovery using only XLOG files in pg_wal, but * will switch to using offline XLOG archives as soon as we reach the end of * WAL in pg_wal. */ bool ArchiveRecoveryRequested = false; bool InArchiveRecovery = false; static bool standby_signal_file_found = false; static bool recovery_signal_file_found = false; /* Was the last xlog file restored from archive, or local? */ static bool restoredFromArchive = false; /* Buffers dedicated to consistency checks of size BLCKSZ */ static char *replay_image_masked = NULL; static char *master_image_masked = NULL; /* options formerly taken from recovery.conf for archive recovery */ char *recoveryRestoreCommand = NULL; char *recoveryEndCommand = NULL; char *archiveCleanupCommand = NULL; RecoveryTargetType recoveryTarget = RECOVERY_TARGET_UNSET; bool recoveryTargetInclusive = true; int recoveryTargetAction = RECOVERY_TARGET_ACTION_PAUSE; TransactionId recoveryTargetXid; char *recovery_target_time_string; static TimestampTz recoveryTargetTime; const char *recoveryTargetName; XLogRecPtr recoveryTargetLSN; int recovery_min_apply_delay = 0; /* options formerly taken from recovery.conf for XLOG streaming */ bool StandbyModeRequested = false; char *PrimaryConnInfo = NULL; char *PrimarySlotName = NULL; char *PromoteTriggerFile = NULL; /* are we currently in standby mode? */ bool StandbyMode = false; /* whether request for fast promotion has been made yet */ static bool fast_promote = false; /* * if recoveryStopsBefore/After returns true, it saves information of the stop * point here */ static TransactionId recoveryStopXid; static TimestampTz recoveryStopTime; static XLogRecPtr recoveryStopLSN; static char recoveryStopName[MAXFNAMELEN]; static bool recoveryStopAfter; /* * During normal operation, the only timeline we care about is ThisTimeLineID. * During recovery, however, things are more complicated. To simplify life * for rmgr code, we keep ThisTimeLineID set to the "current" timeline as we * scan through the WAL history (that is, it is the line that was active when * the currently-scanned WAL record was generated). We also need these * timeline values: * * recoveryTargetTimeLineGoal: what the user requested, if any * * recoveryTargetTLIRequested: numeric value of requested timeline, if constant * * recoveryTargetTLI: the currently understood target timeline; changes * * expectedTLEs: a list of TimeLineHistoryEntries for recoveryTargetTLI and the timelines of * its known parents, newest first (so recoveryTargetTLI is always the * first list member). Only these TLIs are expected to be seen in the WAL * segments we read, and indeed only these TLIs will be considered as * candidate WAL files to open at all. * * curFileTLI: the TLI appearing in the name of the current input WAL file. * (This is not necessarily the same as ThisTimeLineID, because we could * be scanning data that was copied from an ancestor timeline when the current * file was created.) During a sequential scan we do not allow this value * to decrease. */ RecoveryTargetTimeLineGoal recoveryTargetTimeLineGoal = RECOVERY_TARGET_TIMELINE_LATEST; TimeLineID recoveryTargetTLIRequested = 0; TimeLineID recoveryTargetTLI = 0; static List *expectedTLEs; static TimeLineID curFileTLI; /* * ProcLastRecPtr points to the start of the last XLOG record inserted by the * current backend. It is updated for all inserts. XactLastRecEnd points to * end+1 of the last record, and is reset when we end a top-level transaction, * or start a new one; so it can be used to tell if the current transaction has * created any XLOG records. * * While in parallel mode, this may not be fully up to date. When committing, * a transaction can assume this covers all xlog records written either by the * user backend or by any parallel worker which was present at any point during * the transaction. But when aborting, or when still in parallel mode, other * parallel backends may have written WAL records at later LSNs than the value * stored here. The parallel leader advances its own copy, when necessary, * in WaitForParallelWorkersToFinish. */ XLogRecPtr ProcLastRecPtr = InvalidXLogRecPtr; XLogRecPtr XactLastRecEnd = InvalidXLogRecPtr; XLogRecPtr XactLastCommitEnd = InvalidXLogRecPtr; /* * RedoRecPtr is this backend's local copy of the REDO record pointer * (which is almost but not quite the same as a pointer to the most recent * CHECKPOINT record). We update this from the shared-memory copy, * XLogCtl->Insert.RedoRecPtr, whenever we can safely do so (ie, when we * hold an insertion lock). See XLogInsertRecord for details. We are also * allowed to update from XLogCtl->RedoRecPtr if we hold the info_lck; * see GetRedoRecPtr. A freshly spawned backend obtains the value during * InitXLOGAccess. */ static XLogRecPtr RedoRecPtr; /* * doPageWrites is this backend's local copy of (forcePageWrites || * fullPageWrites). It is used together with RedoRecPtr to decide whether * a full-page image of a page need to be taken. */ static bool doPageWrites; /* Has the recovery code requested a walreceiver wakeup? */ static bool doRequestWalReceiverReply; /* * RedoStartLSN points to the checkpoint's REDO location which is specified * in a backup label file, backup history file or control file. In standby * mode, XLOG streaming usually starts from the position where an invalid * record was found. But if we fail to read even the initial checkpoint * record, we use the REDO location instead of the checkpoint location as * the start position of XLOG streaming. Otherwise we would have to jump * backwards to the REDO location after reading the checkpoint record, * because the REDO record can precede the checkpoint record. */ static XLogRecPtr RedoStartLSN = InvalidXLogRecPtr; /*---------- * Shared-memory data structures for XLOG control * * LogwrtRqst indicates a byte position that we need to write and/or fsync * the log up to (all records before that point must be written or fsynced). * LogwrtResult indicates the byte positions we have already written/fsynced. * These structs are identical but are declared separately to indicate their * slightly different functions. * * To read XLogCtl->LogwrtResult, you must hold either info_lck or * WALWriteLock. To update it, you need to hold both locks. The point of * this arrangement is that the value can be examined by code that already * holds WALWriteLock without needing to grab info_lck as well. In addition * to the shared variable, each backend has a private copy of LogwrtResult, * which is updated when convenient. * * The request bookkeeping is simpler: there is a shared XLogCtl->LogwrtRqst * (protected by info_lck), but we don't need to cache any copies of it. * * info_lck is only held long enough to read/update the protected variables, * so it's a plain spinlock. The other locks are held longer (potentially * over I/O operations), so we use LWLocks for them. These locks are: * * WALBufMappingLock: must be held to replace a page in the WAL buffer cache. * It is only held while initializing and changing the mapping. If the * contents of the buffer being replaced haven't been written yet, the mapping * lock is released while the write is done, and reacquired afterwards. * * WALWriteLock: must be held to write WAL buffers to disk (XLogWrite or * XLogFlush). * * ControlFileLock: must be held to read/update control file or create * new log file. * * CheckpointLock: must be held to do a checkpoint or restartpoint (ensures * only one checkpointer at a time; currently, with all checkpoints done by * the checkpointer, this is just pro forma). * *---------- */ typedef struct XLogwrtRqst { XLogRecPtr Write; /* last byte + 1 to write out */ XLogRecPtr Flush; /* last byte + 1 to flush */ } XLogwrtRqst; typedef struct XLogwrtResult { XLogRecPtr Write; /* last byte + 1 written out */ XLogRecPtr Flush; /* last byte + 1 flushed */ } XLogwrtResult; /* * Inserting to WAL is protected by a small fixed number of WAL insertion * locks. To insert to the WAL, you must hold one of the locks - it doesn't * matter which one. To lock out other concurrent insertions, you must hold * of them. Each WAL insertion lock consists of a lightweight lock, plus an * indicator of how far the insertion has progressed (insertingAt). * * The insertingAt values are read when a process wants to flush WAL from * the in-memory buffers to disk, to check that all the insertions to the * region the process is about to write out have finished. You could simply * wait for all currently in-progress insertions to finish, but the * insertingAt indicator allows you to ignore insertions to later in the WAL, * so that you only wait for the insertions that are modifying the buffers * you're about to write out. * * This isn't just an optimization. If all the WAL buffers are dirty, an * inserter that's holding a WAL insert lock might need to evict an old WAL * buffer, which requires flushing the WAL. If it's possible for an inserter * to block on another inserter unnecessarily, deadlock can arise when two * inserters holding a WAL insert lock wait for each other to finish their * insertion. * * Small WAL records that don't cross a page boundary never update the value, * the WAL record is just copied to the page and the lock is released. But * to avoid the deadlock-scenario explained above, the indicator is always * updated before sleeping while holding an insertion lock. * * lastImportantAt contains the LSN of the last important WAL record inserted * using a given lock. This value is used to detect if there has been * important WAL activity since the last time some action, like a checkpoint, * was performed - allowing to not repeat the action if not. The LSN is * updated for all insertions, unless the XLOG_MARK_UNIMPORTANT flag was * set. lastImportantAt is never cleared, only overwritten by the LSN of newer * records. Tracking the WAL activity directly in WALInsertLock has the * advantage of not needing any additional locks to update the value. */ typedef struct { LWLock lock; XLogRecPtr insertingAt; XLogRecPtr lastImportantAt; } WALInsertLock; /* * All the WAL insertion locks are allocated as an array in shared memory. We * force the array stride to be a power of 2, which saves a few cycles in * indexing, but more importantly also ensures that individual slots don't * cross cache line boundaries. (Of course, we have to also ensure that the * array start address is suitably aligned.) */ typedef union WALInsertLockPadded { WALInsertLock l; char pad[PG_CACHE_LINE_SIZE]; } WALInsertLockPadded; /* * State of an exclusive backup, necessary to control concurrent activities * across sessions when working on exclusive backups. * * EXCLUSIVE_BACKUP_NONE means that there is no exclusive backup actually * running, to be more precise pg_start_backup() is not being executed for * an exclusive backup and there is no exclusive backup in progress. * EXCLUSIVE_BACKUP_STARTING means that pg_start_backup() is starting an * exclusive backup. * EXCLUSIVE_BACKUP_IN_PROGRESS means that pg_start_backup() has finished * running and an exclusive backup is in progress. pg_stop_backup() is * needed to finish it. * EXCLUSIVE_BACKUP_STOPPING means that pg_stop_backup() is stopping an * exclusive backup. */ typedef enum ExclusiveBackupState { EXCLUSIVE_BACKUP_NONE = 0, EXCLUSIVE_BACKUP_STARTING, EXCLUSIVE_BACKUP_IN_PROGRESS, EXCLUSIVE_BACKUP_STOPPING } ExclusiveBackupState; /* * Session status of running backup, used for sanity checks in SQL-callable * functions to start and stop backups. */ static SessionBackupState sessionBackupState = SESSION_BACKUP_NONE; /* * Shared state data for WAL insertion. */ typedef struct XLogCtlInsert { slock_t insertpos_lck; /* protects CurrBytePos and PrevBytePos */ /* * CurrBytePos is the end of reserved WAL. The next record will be * inserted at that position. PrevBytePos is the start position of the * previously inserted (or rather, reserved) record - it is copied to the * prev-link of the next record. These are stored as "usable byte * positions" rather than XLogRecPtrs (see XLogBytePosToRecPtr()). */ uint64 CurrBytePos; uint64 PrevBytePos; /* * Make sure the above heavily-contended spinlock and byte positions are * on their own cache line. In particular, the RedoRecPtr and full page * write variables below should be on a different cache line. They are * read on every WAL insertion, but updated rarely, and we don't want * those reads to steal the cache line containing Curr/PrevBytePos. */ char pad[PG_CACHE_LINE_SIZE]; /* * fullPageWrites is the master copy used by all backends to determine * whether to write full-page to WAL, instead of using process-local one. * This is required because, when full_page_writes is changed by SIGHUP, * we must WAL-log it before it actually affects WAL-logging by backends. * Checkpointer sets at startup or after SIGHUP. * * To read these fields, you must hold an insertion lock. To modify them, * you must hold ALL the locks. */ XLogRecPtr RedoRecPtr; /* current redo point for insertions */ bool forcePageWrites; /* forcing full-page writes for PITR? */ bool fullPageWrites; /* * exclusiveBackupState indicates the state of an exclusive backup (see * comments of ExclusiveBackupState for more details). nonExclusiveBackups * is a counter indicating the number of streaming base backups currently * in progress. forcePageWrites is set to true when either of these is * non-zero. lastBackupStart is the latest checkpoint redo location used * as a starting point for an online backup. */ ExclusiveBackupState exclusiveBackupState; int nonExclusiveBackups; XLogRecPtr lastBackupStart; /* * WAL insertion locks. */ WALInsertLockPadded *WALInsertLocks; } XLogCtlInsert; /* * Total shared-memory state for XLOG. */ typedef struct XLogCtlData { XLogCtlInsert Insert; /* Protected by info_lck: */ XLogwrtRqst LogwrtRqst; XLogRecPtr RedoRecPtr; /* a recent copy of Insert->RedoRecPtr */ FullTransactionId ckptFullXid; /* nextFullXid of latest checkpoint */ XLogRecPtr asyncXactLSN; /* LSN of newest async commit/abort */ XLogRecPtr replicationSlotMinLSN; /* oldest LSN needed by any slot */ XLogSegNo lastRemovedSegNo; /* latest removed/recycled XLOG segment */ /* Fake LSN counter, for unlogged relations. Protected by ulsn_lck. */ XLogRecPtr unloggedLSN; slock_t ulsn_lck; /* Time and LSN of last xlog segment switch. Protected by WALWriteLock. */ pg_time_t lastSegSwitchTime; XLogRecPtr lastSegSwitchLSN; /* * Protected by info_lck and WALWriteLock (you must hold either lock to * read it, but both to update) */ XLogwrtResult LogwrtResult; /* * Latest initialized page in the cache (last byte position + 1). * * To change the identity of a buffer (and InitializedUpTo), you need to * hold WALBufMappingLock. To change the identity of a buffer that's * still dirty, the old page needs to be written out first, and for that * you need WALWriteLock, and you need to ensure that there are no * in-progress insertions to the page by calling * WaitXLogInsertionsToFinish(). */ XLogRecPtr InitializedUpTo; /* * These values do not change after startup, although the pointed-to pages * and xlblocks values certainly do. xlblocks values are protected by * WALBufMappingLock. */ char *pages; /* buffers for unwritten XLOG pages */ XLogRecPtr *xlblocks; /* 1st byte ptr-s + XLOG_BLCKSZ */ int XLogCacheBlck; /* highest allocated xlog buffer index */ /* * Shared copy of ThisTimeLineID. Does not change after end-of-recovery. * If we created a new timeline when the system was started up, * PrevTimeLineID is the old timeline's ID that we forked off from. * Otherwise it's equal to ThisTimeLineID. */ TimeLineID ThisTimeLineID; TimeLineID PrevTimeLineID; /* * SharedRecoveryInProgress indicates if we're still in crash or archive * recovery. Protected by info_lck. */ bool SharedRecoveryInProgress; /* * SharedHotStandbyActive indicates if we're still in crash or archive * recovery. Protected by info_lck. */ bool SharedHotStandbyActive; /* * WalWriterSleeping indicates whether the WAL writer is currently in * low-power mode (and hence should be nudged if an async commit occurs). * Protected by info_lck. */ bool WalWriterSleeping; /* * recoveryWakeupLatch is used to wake up the startup process to continue * WAL replay, if it is waiting for WAL to arrive or failover trigger file * to appear. */ Latch recoveryWakeupLatch; /* * During recovery, we keep a copy of the latest checkpoint record here. * lastCheckPointRecPtr points to start of checkpoint record and * lastCheckPointEndPtr points to end+1 of checkpoint record. Used by the * checkpointer when it wants to create a restartpoint. * * Protected by info_lck. */ XLogRecPtr lastCheckPointRecPtr; XLogRecPtr lastCheckPointEndPtr; CheckPoint lastCheckPoint; /* * lastReplayedEndRecPtr points to end+1 of the last record successfully * replayed. When we're currently replaying a record, ie. in a redo * function, replayEndRecPtr points to the end+1 of the record being * replayed, otherwise it's equal to lastReplayedEndRecPtr. */ XLogRecPtr lastReplayedEndRecPtr; TimeLineID lastReplayedTLI; XLogRecPtr replayEndRecPtr; TimeLineID replayEndTLI; /* timestamp of last COMMIT/ABORT record replayed (or being replayed) */ TimestampTz recoveryLastXTime; /* * timestamp of when we started replaying the current chunk of WAL data, * only relevant for replication or archive recovery */ TimestampTz currentChunkStartTime; /* Are we requested to pause recovery? */ bool recoveryPause; /* * lastFpwDisableRecPtr points to the start of the last replayed * XLOG_FPW_CHANGE record that instructs full_page_writes is disabled. */ XLogRecPtr lastFpwDisableRecPtr; slock_t info_lck; /* locks shared variables shown above */ } XLogCtlData; static XLogCtlData *XLogCtl = NULL; /* a private copy of XLogCtl->Insert.WALInsertLocks, for convenience */ static WALInsertLockPadded *WALInsertLocks = NULL; /* * We maintain an image of pg_control in shared memory. */ static ControlFileData *ControlFile = NULL; /* * Calculate the amount of space left on the page after 'endptr'. Beware * multiple evaluation! */ #define INSERT_FREESPACE(endptr) \ (((endptr) % XLOG_BLCKSZ == 0) ? 0 : (XLOG_BLCKSZ - (endptr) % XLOG_BLCKSZ)) /* Macro to advance to next buffer index. */ #define NextBufIdx(idx) \ (((idx) == XLogCtl->XLogCacheBlck) ? 0 : ((idx) + 1)) /* * XLogRecPtrToBufIdx returns the index of the WAL buffer that holds, or * would hold if it was in cache, the page containing 'recptr'. */ #define XLogRecPtrToBufIdx(recptr) \ (((recptr) / XLOG_BLCKSZ) % (XLogCtl->XLogCacheBlck + 1)) /* * These are the number of bytes in a WAL page usable for WAL data. */ #define UsableBytesInPage (XLOG_BLCKSZ - SizeOfXLogShortPHD) /* Convert min_wal_size_mb and max_wal_size_mb to equivalent segment count */ #define ConvertToXSegs(x, segsize) \ (x / ((segsize) / (1024 * 1024))) /* The number of bytes in a WAL segment usable for WAL data. */ static int UsableBytesInSegment; /* * Private, possibly out-of-date copy of shared LogwrtResult. * See discussion above. */ static XLogwrtResult LogwrtResult = {0, 0}; /* * Codes indicating where we got a WAL file from during recovery, or where * to attempt to get one. */ typedef enum { XLOG_FROM_ANY = 0, /* request to read WAL from any source */ XLOG_FROM_ARCHIVE, /* restored using restore_command */ XLOG_FROM_PG_WAL, /* existing file in pg_wal */ XLOG_FROM_STREAM /* streamed from master */ } XLogSource; /* human-readable names for XLogSources, for debugging output */ static const char *const xlogSourceNames[] = {"any", "archive", "pg_wal", "stream"}; /* * openLogFile is -1 or a kernel FD for an open log file segment. * openLogSegNo identifies the segment. These variables are only used to * write the XLOG, and so will normally refer to the active segment. */ static int openLogFile = -1; static XLogSegNo openLogSegNo = 0; /* * These variables are used similarly to the ones above, but for reading * the XLOG. Note, however, that readOff generally represents the offset * of the page just read, not the seek position of the FD itself, which * will be just past that page. readLen indicates how much of the current * page has been read into readBuf, and readSource indicates where we got * the currently open file from. */ static int readFile = -1; static XLogSegNo readSegNo = 0; static uint32 readOff = 0; static uint32 readLen = 0; static XLogSource readSource = 0; /* XLOG_FROM_* code */ /* * Keeps track of which source we're currently reading from. This is * different from readSource in that this is always set, even when we don't * currently have a WAL file open. If lastSourceFailed is set, our last * attempt to read from currentSource failed, and we should try another source * next. */ static XLogSource currentSource = 0; /* XLOG_FROM_* code */ static bool lastSourceFailed = false; typedef struct XLogPageReadPrivate { int emode; bool fetching_ckpt; /* are we fetching a checkpoint record? */ bool randAccess; } XLogPageReadPrivate; /* * These variables track when we last obtained some WAL data to process, * and where we got it from. (XLogReceiptSource is initially the same as * readSource, but readSource gets reset to zero when we don't have data * to process right now. It is also different from currentSource, which * also changes when we try to read from a source and fail, while * XLogReceiptSource tracks where we last successfully read some WAL.) */ static TimestampTz XLogReceiptTime = 0; static XLogSource XLogReceiptSource = 0; /* XLOG_FROM_* code */ /* State information for XLOG reading */ static XLogRecPtr ReadRecPtr; /* start of last record read */ static XLogRecPtr EndRecPtr; /* end+1 of last record read */ /* * Local copies of equivalent fields in the control file. When running * crash recovery, minRecoveryPoint is set to InvalidXLogRecPtr as we * expect to replay all the WAL available, and updateMinRecoveryPoint is * switched to false to prevent any updates while replaying records. * Those values are kept consistent as long as crash recovery runs. */ static XLogRecPtr minRecoveryPoint; static TimeLineID minRecoveryPointTLI; static bool updateMinRecoveryPoint = true; /* * Have we reached a consistent database state? In crash recovery, we have * to replay all the WAL, so reachedConsistency is never set. During archive * recovery, the database is consistent once minRecoveryPoint is reached. */ bool reachedConsistency = false; static bool InRedo = false; /* Have we launched bgwriter during recovery? */ static bool bgwriterLaunched = false; /* For WALInsertLockAcquire/Release functions */ static int MyLockNo = 0; static bool holdingAllLocks = false; #ifdef WAL_DEBUG static MemoryContext walDebugCxt = NULL; #endif static void readRecoverySignalFile(void); static void validateRecoveryParameters(void); static void exitArchiveRecovery(TimeLineID endTLI, XLogRecPtr endOfLog); static bool recoveryStopsBefore(XLogReaderState *record); static bool recoveryStopsAfter(XLogReaderState *record); static void recoveryPausesHere(void); static bool recoveryApplyDelay(XLogReaderState *record); static void SetLatestXTime(TimestampTz xtime); static void SetCurrentChunkStartTime(TimestampTz xtime); static void CheckRequiredParameterValues(void); static void XLogReportParameters(void); static void checkTimeLineSwitch(XLogRecPtr lsn, TimeLineID newTLI, TimeLineID prevTLI); static void LocalSetXLogInsertAllowed(void); static void CreateEndOfRecoveryRecord(void); static void CheckPointGuts(XLogRecPtr checkPointRedo, int flags); static void KeepLogSeg(XLogRecPtr recptr, XLogSegNo *logSegNo); static XLogRecPtr XLogGetReplicationSlotMinimumLSN(void); static void AdvanceXLInsertBuffer(XLogRecPtr upto, bool opportunistic); static bool XLogCheckpointNeeded(XLogSegNo new_segno); static void XLogWrite(XLogwrtRqst WriteRqst, bool flexible); static bool InstallXLogFileSegment(XLogSegNo *segno, char *tmppath, bool find_free, XLogSegNo max_segno, bool use_lock); static int XLogFileRead(XLogSegNo segno, int emode, TimeLineID tli, int source, bool notfoundOk); static int XLogFileReadAnyTLI(XLogSegNo segno, int emode, int source); static int XLogPageRead(XLogReaderState *xlogreader, XLogRecPtr targetPagePtr, int reqLen, XLogRecPtr targetRecPtr, char *readBuf); static bool WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess, bool fetching_ckpt, XLogRecPtr tliRecPtr); static int emode_for_corrupt_record(int emode, XLogRecPtr RecPtr); static void XLogFileClose(void); static void PreallocXlogFiles(XLogRecPtr endptr); static void RemoveTempXlogFiles(void); static void RemoveOldXlogFiles(XLogSegNo segno, XLogRecPtr lastredoptr, XLogRecPtr endptr); static void RemoveXlogFile(const char *segname, XLogRecPtr lastredoptr, XLogRecPtr endptr); static void UpdateLastRemovedPtr(char *filename); static void ValidateXLOGDirectoryStructure(void); static void CleanupBackupHistory(void); static void UpdateMinRecoveryPoint(XLogRecPtr lsn, bool force); static XLogRecord *ReadRecord(XLogReaderState *xlogreader, int emode, bool fetching_ckpt); static void CheckRecoveryConsistency(void); static XLogRecord *ReadCheckpointRecord(XLogReaderState *xlogreader, XLogRecPtr RecPtr, int whichChkpt, bool report); static bool rescanLatestTimeLine(void); static void WriteControlFile(void); static void ReadControlFile(void); static char *str_time(pg_time_t tnow); static bool CheckForStandbyTrigger(void); #ifdef WAL_DEBUG static void xlog_outrec(StringInfo buf, XLogReaderState *record); #endif static void xlog_outdesc(StringInfo buf, XLogReaderState *record); static void pg_start_backup_callback(int code, Datum arg); static void pg_stop_backup_callback(int code, Datum arg); static bool read_backup_label(XLogRecPtr *checkPointLoc, bool *backupEndRequired, bool *backupFromStandby); static bool read_tablespace_map(List **tablespaces); static void rm_redo_error_callback(void *arg); static int get_sync_bit(int method); static void CopyXLogRecordToWAL(int write_len, bool isLogSwitch, XLogRecData *rdata, XLogRecPtr StartPos, XLogRecPtr EndPos); static void ReserveXLogInsertLocation(int size, XLogRecPtr *StartPos, XLogRecPtr *EndPos, XLogRecPtr *PrevPtr); static bool ReserveXLogSwitch(XLogRecPtr *StartPos, XLogRecPtr *EndPos, XLogRecPtr *PrevPtr); static XLogRecPtr WaitXLogInsertionsToFinish(XLogRecPtr upto); static char *GetXLogBuffer(XLogRecPtr ptr); static XLogRecPtr XLogBytePosToRecPtr(uint64 bytepos); static XLogRecPtr XLogBytePosToEndRecPtr(uint64 bytepos); static uint64 XLogRecPtrToBytePos(XLogRecPtr ptr); static void checkXLogConsistency(XLogReaderState *record); static void WALInsertLockAcquire(void); static void WALInsertLockAcquireExclusive(void); static void WALInsertLockRelease(void); static void WALInsertLockUpdateInsertingAt(XLogRecPtr insertingAt); /* * Insert an XLOG record represented by an already-constructed chain of data * chunks. This is a low-level routine; to construct the WAL record header * and data, use the higher-level routines in xloginsert.c. * * If 'fpw_lsn' is valid, it is the oldest LSN among the pages that this * WAL record applies to, that were not included in the record as full page * images. If fpw_lsn <= RedoRecPtr, the function does not perform the * insertion and returns InvalidXLogRecPtr. The caller can then recalculate * which pages need a full-page image, and retry. If fpw_lsn is invalid, the * record is always inserted. * * 'flags' gives more in-depth control on the record being inserted. See * XLogSetRecordFlags() for details. * * The first XLogRecData in the chain must be for the record header, and its * data must be MAXALIGNed. XLogInsertRecord fills in the xl_prev and * xl_crc fields in the header, the rest of the header must already be filled * by the caller. * * Returns XLOG pointer to end of record (beginning of next record). * This can be used as LSN for data pages affected by the logged action. * (LSN is the XLOG point up to which the XLOG must be flushed to disk * before the data page can be written out. This implements the basic * WAL rule "write the log before the data".) */ XLogRecPtr XLogInsertRecord(XLogRecData *rdata, XLogRecPtr fpw_lsn, uint8 flags) { XLogCtlInsert *Insert = &XLogCtl->Insert; pg_crc32c rdata_crc; bool inserted; XLogRecord *rechdr = (XLogRecord *) rdata->data; uint8 info = rechdr->xl_info & ~XLR_INFO_MASK; bool isLogSwitch = (rechdr->xl_rmid == RM_XLOG_ID && info == XLOG_SWITCH); XLogRecPtr StartPos; XLogRecPtr EndPos; bool prevDoPageWrites = doPageWrites; /* we assume that all of the record header is in the first chunk */ Assert(rdata->len >= SizeOfXLogRecord); /* cross-check on whether we should be here or not */ if (!XLogInsertAllowed()) elog(ERROR, "cannot make new WAL entries during recovery"); /*---------- * * We have now done all the preparatory work we can without holding a * lock or modifying shared state. From here on, inserting the new WAL * record to the shared WAL buffer cache is a two-step process: * * 1. Reserve the right amount of space from the WAL. The current head of * reserved space is kept in Insert->CurrBytePos, and is protected by * insertpos_lck. * * 2. Copy the record to the reserved WAL space. This involves finding the * correct WAL buffer containing the reserved space, and copying the * record in place. This can be done concurrently in multiple processes. * * To keep track of which insertions are still in-progress, each concurrent * inserter acquires an insertion lock. In addition to just indicating that * an insertion is in progress, the lock tells others how far the inserter * has progressed. There is a small fixed number of insertion locks, * determined by NUM_XLOGINSERT_LOCKS. When an inserter crosses a page * boundary, it updates the value stored in the lock to the how far it has * inserted, to allow the previous buffer to be flushed. * * Holding onto an insertion lock also protects RedoRecPtr and * fullPageWrites from changing until the insertion is finished. * * Step 2 can usually be done completely in parallel. If the required WAL * page is not initialized yet, you have to grab WALBufMappingLock to * initialize it, but the WAL writer tries to do that ahead of insertions * to avoid that from happening in the critical path. * *---------- */ START_CRIT_SECTION(); if (isLogSwitch) WALInsertLockAcquireExclusive(); else WALInsertLockAcquire(); /* * Check to see if my copy of RedoRecPtr is out of date. If so, may have * to go back and have the caller recompute everything. This can only * happen just after a checkpoint, so it's better to be slow in this case * and fast otherwise. * * Also check to see if fullPageWrites or forcePageWrites was just turned * on; if we weren't already doing full-page writes then go back and * recompute. * * If we aren't doing full-page writes then RedoRecPtr doesn't actually * affect the contents of the XLOG record, so we'll update our local copy * but not force a recomputation. (If doPageWrites was just turned off, * we could recompute the record without full pages, but we choose not to * bother.) */ if (RedoRecPtr != Insert->RedoRecPtr) { Assert(RedoRecPtr < Insert->RedoRecPtr); RedoRecPtr = Insert->RedoRecPtr; } doPageWrites = (Insert->fullPageWrites || Insert->forcePageWrites); if (doPageWrites && (!prevDoPageWrites || (fpw_lsn != InvalidXLogRecPtr && fpw_lsn <= RedoRecPtr))) { /* * Oops, some buffer now needs to be backed up that the caller didn't * back up. Start over. */ WALInsertLockRelease(); END_CRIT_SECTION(); return InvalidXLogRecPtr; } /* * Reserve space for the record in the WAL. This also sets the xl_prev * pointer. */ if (isLogSwitch) inserted = ReserveXLogSwitch(&StartPos, &EndPos, &rechdr->xl_prev); else { ReserveXLogInsertLocation(rechdr->xl_tot_len, &StartPos, &EndPos, &rechdr->xl_prev); inserted = true; } if (inserted) { /* * Now that xl_prev has been filled in, calculate CRC of the record * header. */ rdata_crc = rechdr->xl_crc; COMP_CRC32C(rdata_crc, rechdr, offsetof(XLogRecord, xl_crc)); FIN_CRC32C(rdata_crc); rechdr->xl_crc = rdata_crc; /* * All the record data, including the header, is now ready to be * inserted. Copy the record in the space reserved. */ CopyXLogRecordToWAL(rechdr->xl_tot_len, isLogSwitch, rdata, StartPos, EndPos); /* * Unless record is flagged as not important, update LSN of last * important record in the current slot. When holding all locks, just * update the first one. */ if ((flags & XLOG_MARK_UNIMPORTANT) == 0) { int lockno = holdingAllLocks ? 0 : MyLockNo; WALInsertLocks[lockno].l.lastImportantAt = StartPos; } } else { /* * This was an xlog-switch record, but the current insert location was * already exactly at the beginning of a segment, so there was no need * to do anything. */ } /* * Done! Let others know that we're finished. */ WALInsertLockRelease(); MarkCurrentTransactionIdLoggedIfAny(); END_CRIT_SECTION(); /* * Update shared LogwrtRqst.Write, if we crossed page boundary. */ if (StartPos / XLOG_BLCKSZ != EndPos / XLOG_BLCKSZ) { SpinLockAcquire(&XLogCtl->info_lck); /* advance global request to include new block(s) */ if (XLogCtl->LogwrtRqst.Write < EndPos) XLogCtl->LogwrtRqst.Write = EndPos; /* update local result copy while I have the chance */ LogwrtResult = XLogCtl->LogwrtResult; SpinLockRelease(&XLogCtl->info_lck); } /* * If this was an XLOG_SWITCH record, flush the record and the empty * padding space that fills the rest of the segment, and perform * end-of-segment actions (eg, notifying archiver). */ if (isLogSwitch) { TRACE_POSTGRESQL_WAL_SWITCH(); XLogFlush(EndPos); /* * Even though we reserved the rest of the segment for us, which is * reflected in EndPos, we return a pointer to just the end of the * xlog-switch record. */ if (inserted) { EndPos = StartPos + SizeOfXLogRecord; if (StartPos / XLOG_BLCKSZ != EndPos / XLOG_BLCKSZ) { uint64 offset = XLogSegmentOffset(EndPos, wal_segment_size); if (offset == EndPos % XLOG_BLCKSZ) EndPos += SizeOfXLogLongPHD; else EndPos += SizeOfXLogShortPHD; } } } #ifdef WAL_DEBUG if (XLOG_DEBUG) { static XLogReaderState *debug_reader = NULL; StringInfoData buf; StringInfoData recordBuf; char *errormsg = NULL; MemoryContext oldCxt; oldCxt = MemoryContextSwitchTo(walDebugCxt); initStringInfo(&buf); appendStringInfo(&buf, "INSERT @ %X/%X: ", (uint32) (EndPos >> 32), (uint32) EndPos); /* * We have to piece together the WAL record data from the XLogRecData * entries, so that we can pass it to the rm_desc function as one * contiguous chunk. */ initStringInfo(&recordBuf); for (; rdata != NULL; rdata = rdata->next) appendBinaryStringInfo(&recordBuf, rdata->data, rdata->len); if (!debug_reader) debug_reader = XLogReaderAllocate(wal_segment_size, NULL, NULL, NULL); if (!debug_reader) { appendStringInfoString(&buf, "error decoding record: out of memory"); } else if (!DecodeXLogRecord(debug_reader, (XLogRecord *) recordBuf.data, &errormsg)) { appendStringInfo(&buf, "error decoding record: %s", errormsg ? errormsg : "no error message"); } else { appendStringInfoString(&buf, " - "); xlog_outdesc(&buf, debug_reader); } elog(LOG, "%s", buf.data); pfree(buf.data); pfree(recordBuf.data); MemoryContextSwitchTo(oldCxt); } #endif /* * Update our global variables */ ProcLastRecPtr = StartPos; XactLastRecEnd = EndPos; return EndPos; } /* * Reserves the right amount of space for a record of given size from the WAL. * *StartPos is set to the beginning of the reserved section, *EndPos to * its end+1. *PrevPtr is set to the beginning of the previous record; it is * used to set the xl_prev of this record. * * This is the performance critical part of XLogInsert that must be serialized * across backends. The rest can happen mostly in parallel. Try to keep this * section as short as possible, insertpos_lck can be heavily contended on a * busy system. * * NB: The space calculation here must match the code in CopyXLogRecordToWAL, * where we actually copy the record to the reserved space. */ static void ReserveXLogInsertLocation(int size, XLogRecPtr *StartPos, XLogRecPtr *EndPos, XLogRecPtr *PrevPtr) { XLogCtlInsert *Insert = &XLogCtl->Insert; uint64 startbytepos; uint64 endbytepos; uint64 prevbytepos; size = MAXALIGN(size); /* All (non xlog-switch) records should contain data. */ Assert(size > SizeOfXLogRecord); /* * The duration the spinlock needs to be held is minimized by minimizing * the calculations that have to be done while holding the lock. The * current tip of reserved WAL is kept in CurrBytePos, as a byte position * that only counts "usable" bytes in WAL, that is, it excludes all WAL * page headers. The mapping between "usable" byte positions and physical * positions (XLogRecPtrs) can be done outside the locked region, and * because the usable byte position doesn't include any headers, reserving * X bytes from WAL is almost as simple as "CurrBytePos += X". */ SpinLockAcquire(&Insert->insertpos_lck); startbytepos = Insert->CurrBytePos; endbytepos = startbytepos + size; prevbytepos = Insert->PrevBytePos; Insert->CurrBytePos = endbytepos; Insert->PrevBytePos = startbytepos; SpinLockRelease(&Insert->insertpos_lck); *StartPos = XLogBytePosToRecPtr(startbytepos); *EndPos = XLogBytePosToEndRecPtr(endbytepos); *PrevPtr = XLogBytePosToRecPtr(prevbytepos); /* * Check that the conversions between "usable byte positions" and * XLogRecPtrs work consistently in both directions. */ Assert(XLogRecPtrToBytePos(*StartPos) == startbytepos); Assert(XLogRecPtrToBytePos(*EndPos) == endbytepos); Assert(XLogRecPtrToBytePos(*PrevPtr) == prevbytepos); } /* * Like ReserveXLogInsertLocation(), but for an xlog-switch record. * * A log-switch record is handled slightly differently. The rest of the * segment will be reserved for this insertion, as indicated by the returned * *EndPos value. However, if we are already at the beginning of the current * segment, *StartPos and *EndPos are set to the current location without * reserving any space, and the function returns false. */ static bool ReserveXLogSwitch(XLogRecPtr *StartPos, XLogRecPtr *EndPos, XLogRecPtr *PrevPtr) { XLogCtlInsert *Insert = &XLogCtl->Insert; uint64 startbytepos; uint64 endbytepos; uint64 prevbytepos; uint32 size = MAXALIGN(SizeOfXLogRecord); XLogRecPtr ptr; uint32 segleft; /* * These calculations are a bit heavy-weight to be done while holding a * spinlock, but since we're holding all the WAL insertion locks, there * are no other inserters competing for it. GetXLogInsertRecPtr() does * compete for it, but that's not called very frequently. */ SpinLockAcquire(&Insert->insertpos_lck); startbytepos = Insert->CurrBytePos; ptr = XLogBytePosToEndRecPtr(startbytepos); if (XLogSegmentOffset(ptr, wal_segment_size) == 0) { SpinLockRelease(&Insert->insertpos_lck); *EndPos = *StartPos = ptr; return false; } endbytepos = startbytepos + size; prevbytepos = Insert->PrevBytePos; *StartPos = XLogBytePosToRecPtr(startbytepos); *EndPos = XLogBytePosToEndRecPtr(endbytepos); segleft = wal_segment_size - XLogSegmentOffset(*EndPos, wal_segment_size); if (segleft != wal_segment_size) { /* consume the rest of the segment */ *EndPos += segleft; endbytepos = XLogRecPtrToBytePos(*EndPos); } Insert->CurrBytePos = endbytepos; Insert->PrevBytePos = startbytepos; SpinLockRelease(&Insert->insertpos_lck); *PrevPtr = XLogBytePosToRecPtr(prevbytepos); Assert(XLogSegmentOffset(*EndPos, wal_segment_size) == 0); Assert(XLogRecPtrToBytePos(*EndPos) == endbytepos); Assert(XLogRecPtrToBytePos(*StartPos) == startbytepos); Assert(XLogRecPtrToBytePos(*PrevPtr) == prevbytepos); return true; } /* * Checks whether the current buffer page and backup page stored in the * WAL record are consistent or not. Before comparing the two pages, a * masking can be applied to the pages to ignore certain areas like hint bits, * unused space between pd_lower and pd_upper among other things. This * function should be called once WAL replay has been completed for a * given record. */ static void checkXLogConsistency(XLogReaderState *record) { RmgrId rmid = XLogRecGetRmid(record); RelFileNode rnode; ForkNumber forknum; BlockNumber blkno; int block_id; /* Records with no backup blocks have no need for consistency checks. */ if (!XLogRecHasAnyBlockRefs(record)) return; Assert((XLogRecGetInfo(record) & XLR_CHECK_CONSISTENCY) != 0); for (block_id = 0; block_id <= record->max_block_id; block_id++) { Buffer buf; Page page; if (!XLogRecGetBlockTag(record, block_id, &rnode, &forknum, &blkno)) { /* * WAL record doesn't contain a block reference with the given id. * Do nothing. */ continue; } Assert(XLogRecHasBlockImage(record, block_id)); if (XLogRecBlockImageApply(record, block_id)) { /* * WAL record has already applied the page, so bypass the * consistency check as that would result in comparing the full * page stored in the record with itself. */ continue; } /* * Read the contents from the current buffer and store it in a * temporary page. */ buf = XLogReadBufferExtended(rnode, forknum, blkno, RBM_NORMAL_NO_LOG); if (!BufferIsValid(buf)) continue; LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE); page = BufferGetPage(buf); /* * Take a copy of the local page where WAL has been applied to have a * comparison base before masking it... */ memcpy(replay_image_masked, page, BLCKSZ); /* No need for this page anymore now that a copy is in. */ UnlockReleaseBuffer(buf); /* * If the block LSN is already ahead of this WAL record, we can't * expect contents to match. This can happen if recovery is * restarted. */ if (PageGetLSN(replay_image_masked) > record->EndRecPtr) continue; /* * Read the contents from the backup copy, stored in WAL record and * store it in a temporary page. There is no need to allocate a new * page here, a local buffer is fine to hold its contents and a mask * can be directly applied on it. */ if (!RestoreBlockImage(record, block_id, master_image_masked)) elog(ERROR, "failed to restore block image"); /* * If masking function is defined, mask both the master and replay * images */ if (RmgrTable[rmid].rm_mask != NULL) { RmgrTable[rmid].rm_mask(replay_image_masked, blkno); RmgrTable[rmid].rm_mask(master_image_masked, blkno); } /* Time to compare the master and replay images. */ if (memcmp(replay_image_masked, master_image_masked, BLCKSZ) != 0) { elog(FATAL, "inconsistent page found, rel %u/%u/%u, forknum %u, blkno %u", rnode.spcNode, rnode.dbNode, rnode.relNode, forknum, blkno); } } } /* * Subroutine of XLogInsertRecord. Copies a WAL record to an already-reserved * area in the WAL. */ static void CopyXLogRecordToWAL(int write_len, bool isLogSwitch, XLogRecData *rdata, XLogRecPtr StartPos, XLogRecPtr EndPos) { char *currpos; int freespace; int written; XLogRecPtr CurrPos; XLogPageHeader pagehdr; /* * Get a pointer to the right place in the right WAL buffer to start * inserting to. */ CurrPos = StartPos; currpos = GetXLogBuffer(CurrPos); freespace = INSERT_FREESPACE(CurrPos); /* * there should be enough space for at least the first field (xl_tot_len) * on this page. */ Assert(freespace >= sizeof(uint32)); /* Copy record data */ written = 0; while (rdata != NULL) { char *rdata_data = rdata->data; int rdata_len = rdata->len; while (rdata_len > freespace) { /* * Write what fits on this page, and continue on the next page. */ Assert(CurrPos % XLOG_BLCKSZ >= SizeOfXLogShortPHD || freespace == 0); memcpy(currpos, rdata_data, freespace); rdata_data += freespace; rdata_len -= freespace; written += freespace; CurrPos += freespace; /* * Get pointer to beginning of next page, and set the xlp_rem_len * in the page header. Set XLP_FIRST_IS_CONTRECORD. * * It's safe to set the contrecord flag and xlp_rem_len without a * lock on the page. All the other flags were already set when the * page was initialized, in AdvanceXLInsertBuffer, and we're the * only backend that needs to set the contrecord flag. */ currpos = GetXLogBuffer(CurrPos); pagehdr = (XLogPageHeader) currpos; pagehdr->xlp_rem_len = write_len - written; pagehdr->xlp_info |= XLP_FIRST_IS_CONTRECORD; /* skip over the page header */ if (XLogSegmentOffset(CurrPos, wal_segment_size) == 0) { CurrPos += SizeOfXLogLongPHD; currpos += SizeOfXLogLongPHD; } else { CurrPos += SizeOfXLogShortPHD; currpos += SizeOfXLogShortPHD; } freespace = INSERT_FREESPACE(CurrPos); } Assert(CurrPos % XLOG_BLCKSZ >= SizeOfXLogShortPHD || rdata_len == 0); memcpy(currpos, rdata_data, rdata_len); currpos += rdata_len; CurrPos += rdata_len; freespace -= rdata_len; written += rdata_len; rdata = rdata->next; } Assert(written == write_len); /* * If this was an xlog-switch, it's not enough to write the switch record, * we also have to consume all the remaining space in the WAL segment. We * have already reserved that space, but we need to actually fill it. */ if (isLogSwitch && XLogSegmentOffset(CurrPos, wal_segment_size) != 0) { /* An xlog-switch record doesn't contain any data besides the header */ Assert(write_len == SizeOfXLogRecord); /* Assert that we did reserve the right amount of space */ Assert(XLogSegmentOffset(EndPos, wal_segment_size) == 0); /* Use up all the remaining space on the current page */ CurrPos += freespace; /* * Cause all remaining pages in the segment to be flushed, leaving the * XLog position where it should be, at the start of the next segment. * We do this one page at a time, to make sure we don't deadlock * against ourselves if wal_buffers < wal_segment_size. */ while (CurrPos < EndPos) { /* * The minimal action to flush the page would be to call * WALInsertLockUpdateInsertingAt(CurrPos) followed by * AdvanceXLInsertBuffer(...). The page would be left initialized * mostly to zeros, except for the page header (always the short * variant, as this is never a segment's first page). * * The large vistas of zeros are good for compressibility, but the * headers interrupting them every XLOG_BLCKSZ (with values that * differ from page to page) are not. The effect varies with * compression tool, but bzip2 for instance compresses about an * order of magnitude worse if those headers are left in place. * * Rather than complicating AdvanceXLInsertBuffer itself (which is * called in heavily-loaded circumstances as well as this lightly- * loaded one) with variant behavior, we just use GetXLogBuffer * (which itself calls the two methods we need) to get the pointer * and zero most of the page. Then we just zero the page header. */ currpos = GetXLogBuffer(CurrPos); MemSet(currpos, 0, SizeOfXLogShortPHD); CurrPos += XLOG_BLCKSZ; } } else { /* Align the end position, so that the next record starts aligned */ CurrPos = MAXALIGN64(CurrPos); } if (CurrPos != EndPos) elog(PANIC, "space reserved for WAL record does not match what was written"); } /* * Acquire a WAL insertion lock, for inserting to WAL. */ static void WALInsertLockAcquire(void) { bool immed; /* * It doesn't matter which of the WAL insertion locks we acquire, so try * the one we used last time. If the system isn't particularly busy, it's * a good bet that it's still available, and it's good to have some * affinity to a particular lock so that you don't unnecessarily bounce * cache lines between processes when there's no contention. * * If this is the first time through in this backend, pick a lock * (semi-)randomly. This allows the locks to be used evenly if you have a * lot of very short connections. */ static int lockToTry = -1; if (lockToTry == -1) lockToTry = MyProc->pgprocno % NUM_XLOGINSERT_LOCKS; MyLockNo = lockToTry; /* * The insertingAt value is initially set to 0, as we don't know our * insert location yet. */ immed = LWLockAcquire(&WALInsertLocks[MyLockNo].l.lock, LW_EXCLUSIVE); if (!immed) { /* * If we couldn't get the lock immediately, try another lock next * time. On a system with more insertion locks than concurrent * inserters, this causes all the inserters to eventually migrate to a * lock that no-one else is using. On a system with more inserters * than locks, it still helps to distribute the inserters evenly * across the locks. */ lockToTry = (lockToTry + 1) % NUM_XLOGINSERT_LOCKS; } } /* * Acquire all WAL insertion locks, to prevent other backends from inserting * to WAL. */ static void WALInsertLockAcquireExclusive(void) { int i; /* * When holding all the locks, all but the last lock's insertingAt * indicator is set to 0xFFFFFFFFFFFFFFFF, which is higher than any real * XLogRecPtr value, to make sure that no-one blocks waiting on those. */ for (i = 0; i < NUM_XLOGINSERT_LOCKS - 1; i++) { LWLockAcquire(&WALInsertLocks[i].l.lock, LW_EXCLUSIVE); LWLockUpdateVar(&WALInsertLocks[i].l.lock, &WALInsertLocks[i].l.insertingAt, PG_UINT64_MAX); } /* Variable value reset to 0 at release */ LWLockAcquire(&WALInsertLocks[i].l.lock, LW_EXCLUSIVE); holdingAllLocks = true; } /* * Release our insertion lock (or locks, if we're holding them all). * * NB: Reset all variables to 0, so they cause LWLockWaitForVar to block the * next time the lock is acquired. */ static void WALInsertLockRelease(void) { if (holdingAllLocks) { int i; for (i = 0; i < NUM_XLOGINSERT_LOCKS; i++) LWLockReleaseClearVar(&WALInsertLocks[i].l.lock, &WALInsertLocks[i].l.insertingAt, 0); holdingAllLocks = false; } else { LWLockReleaseClearVar(&WALInsertLocks[MyLockNo].l.lock, &WALInsertLocks[MyLockNo].l.insertingAt, 0); } } /* * Update our insertingAt value, to let others know that we've finished * inserting up to that point. */ static void WALInsertLockUpdateInsertingAt(XLogRecPtr insertingAt) { if (holdingAllLocks) { /* * We use the last lock to mark our actual position, see comments in * WALInsertLockAcquireExclusive. */ LWLockUpdateVar(&WALInsertLocks[NUM_XLOGINSERT_LOCKS - 1].l.lock, &WALInsertLocks[NUM_XLOGINSERT_LOCKS - 1].l.insertingAt, insertingAt); } else LWLockUpdateVar(&WALInsertLocks[MyLockNo].l.lock, &WALInsertLocks[MyLockNo].l.insertingAt, insertingAt); } /* * Wait for any WAL insertions < upto to finish. * * Returns the location of the oldest insertion that is still in-progress. * Any WAL prior to that point has been fully copied into WAL buffers, and * can be flushed out to disk. Because this waits for any insertions older * than 'upto' to finish, the return value is always >= 'upto'. * * Note: When you are about to write out WAL, you must call this function * *before* acquiring WALWriteLock, to avoid deadlocks. This function might * need to wait for an insertion to finish (or at least advance to next * uninitialized page), and the inserter might need to evict an old WAL buffer * to make room for a new one, which in turn requires WALWriteLock. */ static XLogRecPtr WaitXLogInsertionsToFinish(XLogRecPtr upto) { uint64 bytepos; XLogRecPtr reservedUpto; XLogRecPtr finishedUpto; XLogCtlInsert *Insert = &XLogCtl->Insert; int i; if (MyProc == NULL) elog(PANIC, "cannot wait without a PGPROC structure"); /* Read the current insert position */ SpinLockAcquire(&Insert->insertpos_lck); bytepos = Insert->CurrBytePos; SpinLockRelease(&Insert->insertpos_lck); reservedUpto = XLogBytePosToEndRecPtr(bytepos); /* * No-one should request to flush a piece of WAL that hasn't even been * reserved yet. However, it can happen if there is a block with a bogus * LSN on disk, for example. XLogFlush checks for that situation and * complains, but only after the flush. Here we just assume that to mean * that all WAL that has been reserved needs to be finished. In this * corner-case, the return value can be smaller than 'upto' argument. */ if (upto > reservedUpto) { elog(LOG, "request to flush past end of generated WAL; request %X/%X, currpos %X/%X", (uint32) (upto >> 32), (uint32) upto, (uint32) (reservedUpto >> 32), (uint32) reservedUpto); upto = reservedUpto; } /* * Loop through all the locks, sleeping on any in-progress insert older * than 'upto'. * * finishedUpto is our return value, indicating the point upto which all * the WAL insertions have been finished. Initialize it to the head of * reserved WAL, and as we iterate through the insertion locks, back it * out for any insertion that's still in progress. */ finishedUpto = reservedUpto; for (i = 0; i < NUM_XLOGINSERT_LOCKS; i++) { XLogRecPtr insertingat = InvalidXLogRecPtr; do { /* * See if this insertion is in progress. LWLockWaitForVar will * wait for the lock to be released, or for the 'value' to be set * by a LWLockUpdateVar call. When a lock is initially acquired, * its value is 0 (InvalidXLogRecPtr), which means that we don't * know where it's inserting yet. We will have to wait for it. If * it's a small insertion, the record will most likely fit on the * same page and the inserter will release the lock without ever * calling LWLockUpdateVar. But if it has to sleep, it will * advertise the insertion point with LWLockUpdateVar before * sleeping. */ if (LWLockWaitForVar(&WALInsertLocks[i].l.lock, &WALInsertLocks[i].l.insertingAt, insertingat, &insertingat)) { /* the lock was free, so no insertion in progress */ insertingat = InvalidXLogRecPtr; break; } /* * This insertion is still in progress. Have to wait, unless the * inserter has proceeded past 'upto'. */ } while (insertingat < upto); if (insertingat != InvalidXLogRecPtr && insertingat < finishedUpto) finishedUpto = insertingat; } return finishedUpto; } /* * Get a pointer to the right location in the WAL buffer containing the * given XLogRecPtr. * * If the page is not initialized yet, it is initialized. That might require * evicting an old dirty buffer from the buffer cache, which means I/O. * * The caller must ensure that the page containing the requested location * isn't evicted yet, and won't be evicted. The way to ensure that is to * hold onto a WAL insertion lock with the insertingAt position set to * something <= ptr. GetXLogBuffer() will update insertingAt if it needs * to evict an old page from the buffer. (This means that once you call * GetXLogBuffer() with a given 'ptr', you must not access anything before * that point anymore, and must not call GetXLogBuffer() with an older 'ptr' * later, because older buffers might be recycled already) */ static char * GetXLogBuffer(XLogRecPtr ptr) { int idx; XLogRecPtr endptr; static uint64 cachedPage = 0; static char *cachedPos = NULL; XLogRecPtr expectedEndPtr; /* * Fast path for the common case that we need to access again the same * page as last time. */ if (ptr / XLOG_BLCKSZ == cachedPage) { Assert(((XLogPageHeader) cachedPos)->xlp_magic == XLOG_PAGE_MAGIC); Assert(((XLogPageHeader) cachedPos)->xlp_pageaddr == ptr - (ptr % XLOG_BLCKSZ)); return cachedPos + ptr % XLOG_BLCKSZ; } /* * The XLog buffer cache is organized so that a page is always loaded to a * particular buffer. That way we can easily calculate the buffer a given * page must be loaded into, from the XLogRecPtr alone. */ idx = XLogRecPtrToBufIdx(ptr); /* * See what page is loaded in the buffer at the moment. It could be the * page we're looking for, or something older. It can't be anything newer * - that would imply the page we're looking for has already been written * out to disk and evicted, and the caller is responsible for making sure * that doesn't happen. * * However, we don't hold a lock while we read the value. If someone has * just initialized the page, it's possible that we get a "torn read" of * the XLogRecPtr if 64-bit fetches are not atomic on this platform. In * that case we will see a bogus value. That's ok, we'll grab the mapping * lock (in AdvanceXLInsertBuffer) and retry if we see anything else than * the page we're looking for. But it means that when we do this unlocked * read, we might see a value that appears to be ahead of the page we're * looking for. Don't PANIC on that, until we've verified the value while * holding the lock. */ expectedEndPtr = ptr; expectedEndPtr += XLOG_BLCKSZ - ptr % XLOG_BLCKSZ; endptr = XLogCtl->xlblocks[idx]; if (expectedEndPtr != endptr) { XLogRecPtr initializedUpto; /* * Before calling AdvanceXLInsertBuffer(), which can block, let others * know how far we're finished with inserting the record. * * NB: If 'ptr' points to just after the page header, advertise a * position at the beginning of the page rather than 'ptr' itself. If * there are no other insertions running, someone might try to flush * up to our advertised location. If we advertised a position after * the page header, someone might try to flush the page header, even * though page might actually not be initialized yet. As the first * inserter on the page, we are effectively responsible for making * sure that it's initialized, before we let insertingAt to move past * the page header. */ if (ptr % XLOG_BLCKSZ == SizeOfXLogShortPHD && XLogSegmentOffset(ptr, wal_segment_size) > XLOG_BLCKSZ) initializedUpto = ptr - SizeOfXLogShortPHD; else if (ptr % XLOG_BLCKSZ == SizeOfXLogLongPHD && XLogSegmentOffset(ptr, wal_segment_size) < XLOG_BLCKSZ) initializedUpto = ptr - SizeOfXLogLongPHD; else initializedUpto = ptr; WALInsertLockUpdateInsertingAt(initializedUpto); AdvanceXLInsertBuffer(ptr, false); endptr = XLogCtl->xlblocks[idx]; if (expectedEndPtr != endptr) elog(PANIC, "could not find WAL buffer for %X/%X", (uint32) (ptr >> 32), (uint32) ptr); } else { /* * Make sure the initialization of the page is visible to us, and * won't arrive later to overwrite the WAL data we write on the page. */ pg_memory_barrier(); } /* * Found the buffer holding this page. Return a pointer to the right * offset within the page. */ cachedPage = ptr / XLOG_BLCKSZ; cachedPos = XLogCtl->pages + idx * (Size) XLOG_BLCKSZ; Assert(((XLogPageHeader) cachedPos)->xlp_magic == XLOG_PAGE_MAGIC); Assert(((XLogPageHeader) cachedPos)->xlp_pageaddr == ptr - (ptr % XLOG_BLCKSZ)); return cachedPos + ptr % XLOG_BLCKSZ; } /* * Converts a "usable byte position" to XLogRecPtr. A usable byte position * is the position starting from the beginning of WAL, excluding all WAL * page headers. */ static XLogRecPtr XLogBytePosToRecPtr(uint64 bytepos) { uint64 fullsegs; uint64 fullpages; uint64 bytesleft; uint32 seg_offset; XLogRecPtr result; fullsegs = bytepos / UsableBytesInSegment; bytesleft = bytepos % UsableBytesInSegment; if (bytesleft < XLOG_BLCKSZ - SizeOfXLogLongPHD) { /* fits on first page of segment */ seg_offset = bytesleft + SizeOfXLogLongPHD; } else { /* account for the first page on segment with long header */ seg_offset = XLOG_BLCKSZ; bytesleft -= XLOG_BLCKSZ - SizeOfXLogLongPHD; fullpages = bytesleft / UsableBytesInPage; bytesleft = bytesleft % UsableBytesInPage; seg_offset += fullpages * XLOG_BLCKSZ + bytesleft + SizeOfXLogShortPHD; } XLogSegNoOffsetToRecPtr(fullsegs, seg_offset, wal_segment_size, result); return result; } /* * Like XLogBytePosToRecPtr, but if the position is at a page boundary, * returns a pointer to the beginning of the page (ie. before page header), * not to where the first xlog record on that page would go to. This is used * when converting a pointer to the end of a record. */ static XLogRecPtr XLogBytePosToEndRecPtr(uint64 bytepos) { uint64 fullsegs; uint64 fullpages; uint64 bytesleft; uint32 seg_offset; XLogRecPtr result; fullsegs = bytepos / UsableBytesInSegment; bytesleft = bytepos % UsableBytesInSegment; if (bytesleft < XLOG_BLCKSZ - SizeOfXLogLongPHD) { /* fits on first page of segment */ if (bytesleft == 0) seg_offset = 0; else seg_offset = bytesleft + SizeOfXLogLongPHD; } else { /* account for the first page on segment with long header */ seg_offset = XLOG_BLCKSZ; bytesleft -= XLOG_BLCKSZ - SizeOfXLogLongPHD; fullpages = bytesleft / UsableBytesInPage; bytesleft = bytesleft % UsableBytesInPage; if (bytesleft == 0) seg_offset += fullpages * XLOG_BLCKSZ + bytesleft; else seg_offset += fullpages * XLOG_BLCKSZ + bytesleft + SizeOfXLogShortPHD; } XLogSegNoOffsetToRecPtr(fullsegs, seg_offset, wal_segment_size, result); return result; } /* * Convert an XLogRecPtr to a "usable byte position". */ static uint64 XLogRecPtrToBytePos(XLogRecPtr ptr) { uint64 fullsegs; uint32 fullpages; uint32 offset; uint64 result; XLByteToSeg(ptr, fullsegs, wal_segment_size); fullpages = (XLogSegmentOffset(ptr, wal_segment_size)) / XLOG_BLCKSZ; offset = ptr % XLOG_BLCKSZ; if (fullpages == 0) { result = fullsegs * UsableBytesInSegment; if (offset > 0) { Assert(offset >= SizeOfXLogLongPHD); result += offset - SizeOfXLogLongPHD; } } else { result = fullsegs * UsableBytesInSegment + (XLOG_BLCKSZ - SizeOfXLogLongPHD) + /* account for first page */ (fullpages - 1) * UsableBytesInPage; /* full pages */ if (offset > 0) { Assert(offset >= SizeOfXLogShortPHD); result += offset - SizeOfXLogShortPHD; } } return result; } /* * Initialize XLOG buffers, writing out old buffers if they still contain * unwritten data, upto the page containing 'upto'. Or if 'opportunistic' is * true, initialize as many pages as we can without having to write out * unwritten data. Any new pages are initialized to zeros, with pages headers * initialized properly. */ static void AdvanceXLInsertBuffer(XLogRecPtr upto, bool opportunistic) { XLogCtlInsert *Insert = &XLogCtl->Insert; int nextidx; XLogRecPtr OldPageRqstPtr; XLogwrtRqst WriteRqst; XLogRecPtr NewPageEndPtr = InvalidXLogRecPtr; XLogRecPtr NewPageBeginPtr; XLogPageHeader NewPage; int npages = 0; LWLockAcquire(WALBufMappingLock, LW_EXCLUSIVE); /* * Now that we have the lock, check if someone initialized the page * already. */ while (upto >= XLogCtl->InitializedUpTo || opportunistic) { nextidx = XLogRecPtrToBufIdx(XLogCtl->InitializedUpTo); /* * Get ending-offset of the buffer page we need to replace (this may * be zero if the buffer hasn't been used yet). Fall through if it's * already written out. */ OldPageRqstPtr = XLogCtl->xlblocks[nextidx]; if (LogwrtResult.Write < OldPageRqstPtr) { /* * Nope, got work to do. If we just want to pre-initialize as much * as we can without flushing, give up now. */ if (opportunistic) break; /* Before waiting, get info_lck and update LogwrtResult */ SpinLockAcquire(&XLogCtl->info_lck); if (XLogCtl->LogwrtRqst.Write < OldPageRqstPtr) XLogCtl->LogwrtRqst.Write = OldPageRqstPtr; LogwrtResult = XLogCtl->LogwrtResult; SpinLockRelease(&XLogCtl->info_lck); /* * Now that we have an up-to-date LogwrtResult value, see if we * still need to write it or if someone else already did. */ if (LogwrtResult.Write < OldPageRqstPtr) { /* * Must acquire write lock. Release WALBufMappingLock first, * to make sure that all insertions that we need to wait for * can finish (up to this same position). Otherwise we risk * deadlock. */ LWLockRelease(WALBufMappingLock); WaitXLogInsertionsToFinish(OldPageRqstPtr); LWLockAcquire(WALWriteLock, LW_EXCLUSIVE); LogwrtResult = XLogCtl->LogwrtResult; if (LogwrtResult.Write >= OldPageRqstPtr) { /* OK, someone wrote it already */ LWLockRelease(WALWriteLock); } else { /* Have to write it ourselves */ TRACE_POSTGRESQL_WAL_BUFFER_WRITE_DIRTY_START(); WriteRqst.Write = OldPageRqstPtr; WriteRqst.Flush = 0; XLogWrite(WriteRqst, false); LWLockRelease(WALWriteLock); TRACE_POSTGRESQL_WAL_BUFFER_WRITE_DIRTY_DONE(); } /* Re-acquire WALBufMappingLock and retry */ LWLockAcquire(WALBufMappingLock, LW_EXCLUSIVE); continue; } } /* * Now the next buffer slot is free and we can set it up to be the * next output page. */ NewPageBeginPtr = XLogCtl->InitializedUpTo; NewPageEndPtr = NewPageBeginPtr + XLOG_BLCKSZ; Assert(XLogRecPtrToBufIdx(NewPageBeginPtr) == nextidx); NewPage = (XLogPageHeader) (XLogCtl->pages + nextidx * (Size) XLOG_BLCKSZ); /* * Be sure to re-zero the buffer so that bytes beyond what we've * written will look like zeroes and not valid XLOG records... */ MemSet((char *) NewPage, 0, XLOG_BLCKSZ); /* * Fill the new page's header */ NewPage->xlp_magic = XLOG_PAGE_MAGIC; /* NewPage->xlp_info = 0; */ /* done by memset */ NewPage->xlp_tli = ThisTimeLineID; NewPage->xlp_pageaddr = NewPageBeginPtr; /* NewPage->xlp_rem_len = 0; */ /* done by memset */ /* * If online backup is not in progress, mark the header to indicate * that WAL records beginning in this page have removable backup * blocks. This allows the WAL archiver to know whether it is safe to * compress archived WAL data by transforming full-block records into * the non-full-block format. It is sufficient to record this at the * page level because we force a page switch (in fact a segment * switch) when starting a backup, so the flag will be off before any * records can be written during the backup. At the end of a backup, * the last page will be marked as all unsafe when perhaps only part * is unsafe, but at worst the archiver would miss the opportunity to * compress a few records. */ if (!Insert->forcePageWrites) NewPage->xlp_info |= XLP_BKP_REMOVABLE; /* * If first page of an XLOG segment file, make it a long header. */ if ((XLogSegmentOffset(NewPage->xlp_pageaddr, wal_segment_size)) == 0) { XLogLongPageHeader NewLongPage = (XLogLongPageHeader) NewPage; NewLongPage->xlp_sysid = ControlFile->system_identifier; NewLongPage->xlp_seg_size = wal_segment_size; NewLongPage->xlp_xlog_blcksz = XLOG_BLCKSZ; NewPage->xlp_info |= XLP_LONG_HEADER; } /* * Make sure the initialization of the page becomes visible to others * before the xlblocks update. GetXLogBuffer() reads xlblocks without * holding a lock. */ pg_write_barrier(); *((volatile XLogRecPtr *) &XLogCtl->xlblocks[nextidx]) = NewPageEndPtr; XLogCtl->InitializedUpTo = NewPageEndPtr; npages++; } LWLockRelease(WALBufMappingLock); #ifdef WAL_DEBUG if (XLOG_DEBUG && npages > 0) { elog(DEBUG1, "initialized %d pages, up to %X/%X", npages, (uint32) (NewPageEndPtr >> 32), (uint32) NewPageEndPtr); } #endif } /* * Calculate CheckPointSegments based on max_wal_size_mb and * checkpoint_completion_target. */ static void CalculateCheckpointSegments(void) { double target; /*------- * Calculate the distance at which to trigger a checkpoint, to avoid * exceeding max_wal_size_mb. This is based on two assumptions: * * a) we keep WAL for only one checkpoint cycle (prior to PG11 we kept * WAL for two checkpoint cycles to allow us to recover from the * secondary checkpoint if the first checkpoint failed, though we * only did this on the master anyway, not on standby. Keeping just * one checkpoint simplifies processing and reduces disk space in * many smaller databases.) * b) during checkpoint, we consume checkpoint_completion_target * * number of segments consumed between checkpoints. *------- */ target = (double) ConvertToXSegs(max_wal_size_mb, wal_segment_size) / (1.0 + CheckPointCompletionTarget); /* round down */ CheckPointSegments = (int) target; if (CheckPointSegments < 1) CheckPointSegments = 1; } void assign_max_wal_size(int newval, void *extra) { max_wal_size_mb = newval; CalculateCheckpointSegments(); } void assign_checkpoint_completion_target(double newval, void *extra) { CheckPointCompletionTarget = newval; CalculateCheckpointSegments(); } /* * At a checkpoint, how many WAL segments to recycle as preallocated future * XLOG segments? Returns the highest segment that should be preallocated. */ static XLogSegNo XLOGfileslop(XLogRecPtr lastredoptr) { XLogSegNo minSegNo; XLogSegNo maxSegNo; double distance; XLogSegNo recycleSegNo; /* * Calculate the segment numbers that min_wal_size_mb and max_wal_size_mb * correspond to. Always recycle enough segments to meet the minimum, and * remove enough segments to stay below the maximum. */ minSegNo = lastredoptr / wal_segment_size + ConvertToXSegs(min_wal_size_mb, wal_segment_size) - 1; maxSegNo = lastredoptr / wal_segment_size + ConvertToXSegs(max_wal_size_mb, wal_segment_size) - 1; /* * Between those limits, recycle enough segments to get us through to the * estimated end of next checkpoint. * * To estimate where the next checkpoint will finish, assume that the * system runs steadily consuming CheckPointDistanceEstimate bytes between * every checkpoint. */ distance = (1.0 + CheckPointCompletionTarget) * CheckPointDistanceEstimate; /* add 10% for good measure. */ distance *= 1.10; recycleSegNo = (XLogSegNo) ceil(((double) lastredoptr + distance) / wal_segment_size); if (recycleSegNo < minSegNo) recycleSegNo = minSegNo; if (recycleSegNo > maxSegNo) recycleSegNo = maxSegNo; return recycleSegNo; } /* * Check whether we've consumed enough xlog space that a checkpoint is needed. * * new_segno indicates a log file that has just been filled up (or read * during recovery). We measure the distance from RedoRecPtr to new_segno * and see if that exceeds CheckPointSegments. * * Note: it is caller's responsibility that RedoRecPtr is up-to-date. */ static bool XLogCheckpointNeeded(XLogSegNo new_segno) { XLogSegNo old_segno; XLByteToSeg(RedoRecPtr, old_segno, wal_segment_size); if (new_segno >= old_segno + (uint64) (CheckPointSegments - 1)) return true; return false; } /* * Write and/or fsync the log at least as far as WriteRqst indicates. * * If flexible == true, we don't have to write as far as WriteRqst, but * may stop at any convenient boundary (such as a cache or logfile boundary). * This option allows us to avoid uselessly issuing multiple writes when a * single one would do. * * Must be called with WALWriteLock held. WaitXLogInsertionsToFinish(WriteRqst) * must be called before grabbing the lock, to make sure the data is ready to * write. */ static void XLogWrite(XLogwrtRqst WriteRqst, bool flexible) { bool ispartialpage; bool last_iteration; bool finishing_seg; bool use_existent; int curridx; int npages; int startidx; uint32 startoffset; /* We should always be inside a critical section here */ Assert(CritSectionCount > 0); /* * Update local LogwrtResult (caller probably did this already, but...) */ LogwrtResult = XLogCtl->LogwrtResult; /* * Since successive pages in the xlog cache are consecutively allocated, * we can usually gather multiple pages together and issue just one * write() call. npages is the number of pages we have determined can be * written together; startidx is the cache block index of the first one, * and startoffset is the file offset at which it should go. The latter * two variables are only valid when npages > 0, but we must initialize * all of them to keep the compiler quiet. */ npages = 0; startidx = 0; startoffset = 0; /* * Within the loop, curridx is the cache block index of the page to * consider writing. Begin at the buffer containing the next unwritten * page, or last partially written page. */ curridx = XLogRecPtrToBufIdx(LogwrtResult.Write); while (LogwrtResult.Write < WriteRqst.Write) { /* * Make sure we're not ahead of the insert process. This could happen * if we're passed a bogus WriteRqst.Write that is past the end of the * last page that's been initialized by AdvanceXLInsertBuffer. */ XLogRecPtr EndPtr = XLogCtl->xlblocks[curridx]; if (LogwrtResult.Write >= EndPtr) elog(PANIC, "xlog write request %X/%X is past end of log %X/%X", (uint32) (LogwrtResult.Write >> 32), (uint32) LogwrtResult.Write, (uint32) (EndPtr >> 32), (uint32) EndPtr); /* Advance LogwrtResult.Write to end of current buffer page */ LogwrtResult.Write = EndPtr; ispartialpage = WriteRqst.Write < LogwrtResult.Write; if (!XLByteInPrevSeg(LogwrtResult.Write, openLogSegNo, wal_segment_size)) { /* * Switch to new logfile segment. We cannot have any pending * pages here (since we dump what we have at segment end). */ Assert(npages == 0); if (openLogFile >= 0) XLogFileClose(); XLByteToPrevSeg(LogwrtResult.Write, openLogSegNo, wal_segment_size); /* create/use new log file */ use_existent = true; openLogFile = XLogFileInit(openLogSegNo, &use_existent, true); } /* Make sure we have the current logfile open */ if (openLogFile < 0) { XLByteToPrevSeg(LogwrtResult.Write, openLogSegNo, wal_segment_size); openLogFile = XLogFileOpen(openLogSegNo); } /* Add current page to the set of pending pages-to-dump */ if (npages == 0) { /* first of group */ startidx = curridx; startoffset = XLogSegmentOffset(LogwrtResult.Write - XLOG_BLCKSZ, wal_segment_size); } npages++; /* * Dump the set if this will be the last loop iteration, or if we are * at the last page of the cache area (since the next page won't be * contiguous in memory), or if we are at the end of the logfile * segment. */ last_iteration = WriteRqst.Write <= LogwrtResult.Write; finishing_seg = !ispartialpage && (startoffset + npages * XLOG_BLCKSZ) >= wal_segment_size; if (last_iteration || curridx == XLogCtl->XLogCacheBlck || finishing_seg) { char *from; Size nbytes; Size nleft; int written; /* OK to write the page(s) */ from = XLogCtl->pages + startidx * (Size) XLOG_BLCKSZ; nbytes = npages * (Size) XLOG_BLCKSZ; nleft = nbytes; do { errno = 0; pgstat_report_wait_start(WAIT_EVENT_WAL_WRITE); written = pg_pwrite(openLogFile, from, nleft, startoffset); pgstat_report_wait_end(); if (written <= 0) { char xlogfname[MAXFNAMELEN]; int save_errno; if (errno == EINTR) continue; save_errno = errno; XLogFileName(xlogfname, ThisTimeLineID, openLogSegNo, wal_segment_size); errno = save_errno; ereport(PANIC, (errcode_for_file_access(), errmsg("could not write to log file %s " "at offset %u, length %zu: %m", xlogfname, startoffset, nleft))); } nleft -= written; from += written; startoffset += written; } while (nleft > 0); npages = 0; /* * If we just wrote the whole last page of a logfile segment, * fsync the segment immediately. This avoids having to go back * and re-open prior segments when an fsync request comes along * later. Doing it here ensures that one and only one backend will * perform this fsync. * * This is also the right place to notify the Archiver that the * segment is ready to copy to archival storage, and to update the * timer for archive_timeout, and to signal for a checkpoint if * too many logfile segments have been used since the last * checkpoint. */ if (finishing_seg) { issue_xlog_fsync(openLogFile, openLogSegNo); /* signal that we need to wakeup walsenders later */ WalSndWakeupRequest(); LogwrtResult.Flush = LogwrtResult.Write; /* end of page */ if (XLogArchivingActive()) XLogArchiveNotifySeg(openLogSegNo); XLogCtl->lastSegSwitchTime = (pg_time_t) time(NULL); XLogCtl->lastSegSwitchLSN = LogwrtResult.Flush; /* * Request a checkpoint if we've consumed too much xlog since * the last one. For speed, we first check using the local * copy of RedoRecPtr, which might be out of date; if it looks * like a checkpoint is needed, forcibly update RedoRecPtr and * recheck. */ if (IsUnderPostmaster && XLogCheckpointNeeded(openLogSegNo)) { (void) GetRedoRecPtr(); if (XLogCheckpointNeeded(openLogSegNo)) RequestCheckpoint(CHECKPOINT_CAUSE_XLOG); } } } if (ispartialpage) { /* Only asked to write a partial page */ LogwrtResult.Write = WriteRqst.Write; break; } curridx = NextBufIdx(curridx); /* If flexible, break out of loop as soon as we wrote something */ if (flexible && npages == 0) break; } Assert(npages == 0); /* * If asked to flush, do so */ if (LogwrtResult.Flush < WriteRqst.Flush && LogwrtResult.Flush < LogwrtResult.Write) { /* * Could get here without iterating above loop, in which case we might * have no open file or the wrong one. However, we do not need to * fsync more than one file. */ if (sync_method != SYNC_METHOD_OPEN && sync_method != SYNC_METHOD_OPEN_DSYNC) { if (openLogFile >= 0 && !XLByteInPrevSeg(LogwrtResult.Write, openLogSegNo, wal_segment_size)) XLogFileClose(); if (openLogFile < 0) { XLByteToPrevSeg(LogwrtResult.Write, openLogSegNo, wal_segment_size); openLogFile = XLogFileOpen(openLogSegNo); } issue_xlog_fsync(openLogFile, openLogSegNo); } /* signal that we need to wakeup walsenders later */ WalSndWakeupRequest(); LogwrtResult.Flush = LogwrtResult.Write; } /* * Update shared-memory status * * We make sure that the shared 'request' values do not fall behind the * 'result' values. This is not absolutely essential, but it saves some * code in a couple of places. */ { SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->LogwrtResult = LogwrtResult; if (XLogCtl->LogwrtRqst.Write < LogwrtResult.Write) XLogCtl->LogwrtRqst.Write = LogwrtResult.Write; if (XLogCtl->LogwrtRqst.Flush < LogwrtResult.Flush) XLogCtl->LogwrtRqst.Flush = LogwrtResult.Flush; SpinLockRelease(&XLogCtl->info_lck); } } /* * Record the LSN for an asynchronous transaction commit/abort * and nudge the WALWriter if there is work for it to do. * (This should not be called for synchronous commits.) */ void XLogSetAsyncXactLSN(XLogRecPtr asyncXactLSN) { XLogRecPtr WriteRqstPtr = asyncXactLSN; bool sleeping; SpinLockAcquire(&XLogCtl->info_lck); LogwrtResult = XLogCtl->LogwrtResult; sleeping = XLogCtl->WalWriterSleeping; if (XLogCtl->asyncXactLSN < asyncXactLSN) XLogCtl->asyncXactLSN = asyncXactLSN; SpinLockRelease(&XLogCtl->info_lck); /* * If the WALWriter is sleeping, we should kick it to make it come out of * low-power mode. Otherwise, determine whether there's a full page of * WAL available to write. */ if (!sleeping) { /* back off to last completed page boundary */ WriteRqstPtr -= WriteRqstPtr % XLOG_BLCKSZ; /* if we have already flushed that far, we're done */ if (WriteRqstPtr <= LogwrtResult.Flush) return; } /* * Nudge the WALWriter: it has a full page of WAL to write, or we want it * to come out of low-power mode so that this async commit will reach disk * within the expected amount of time. */ if (ProcGlobal->walwriterLatch) SetLatch(ProcGlobal->walwriterLatch); } /* * Record the LSN up to which we can remove WAL because it's not required by * any replication slot. */ void XLogSetReplicationSlotMinimumLSN(XLogRecPtr lsn) { SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->replicationSlotMinLSN = lsn; SpinLockRelease(&XLogCtl->info_lck); } /* * Return the oldest LSN we must retain to satisfy the needs of some * replication slot. */ static XLogRecPtr XLogGetReplicationSlotMinimumLSN(void) { XLogRecPtr retval; SpinLockAcquire(&XLogCtl->info_lck); retval = XLogCtl->replicationSlotMinLSN; SpinLockRelease(&XLogCtl->info_lck); return retval; } /* * Advance minRecoveryPoint in control file. * * If we crash during recovery, we must reach this point again before the * database is consistent. * * If 'force' is true, 'lsn' argument is ignored. Otherwise, minRecoveryPoint * is only updated if it's not already greater than or equal to 'lsn'. */ static void UpdateMinRecoveryPoint(XLogRecPtr lsn, bool force) { /* Quick check using our local copy of the variable */ if (!updateMinRecoveryPoint || (!force && lsn <= minRecoveryPoint)) return; /* * An invalid minRecoveryPoint means that we need to recover all the WAL, * i.e., we're doing crash recovery. We never modify the control file's * value in that case, so we can short-circuit future checks here too. The * local values of minRecoveryPoint and minRecoveryPointTLI should not be * updated until crash recovery finishes. We only do this for the startup * process as it should not update its own reference of minRecoveryPoint * until it has finished crash recovery to make sure that all WAL * available is replayed in this case. This also saves from extra locks * taken on the control file from the startup process. */ if (XLogRecPtrIsInvalid(minRecoveryPoint) && InRecovery) { updateMinRecoveryPoint = false; return; } LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); /* update local copy */ minRecoveryPoint = ControlFile->minRecoveryPoint; minRecoveryPointTLI = ControlFile->minRecoveryPointTLI; if (XLogRecPtrIsInvalid(minRecoveryPoint)) updateMinRecoveryPoint = false; else if (force || minRecoveryPoint < lsn) { XLogRecPtr newMinRecoveryPoint; TimeLineID newMinRecoveryPointTLI; /* * To avoid having to update the control file too often, we update it * all the way to the last record being replayed, even though 'lsn' * would suffice for correctness. This also allows the 'force' case * to not need a valid 'lsn' value. * * Another important reason for doing it this way is that the passed * 'lsn' value could be bogus, i.e., past the end of available WAL, if * the caller got it from a corrupted heap page. Accepting such a * value as the min recovery point would prevent us from coming up at * all. Instead, we just log a warning and continue with recovery. * (See also the comments about corrupt LSNs in XLogFlush.) */ SpinLockAcquire(&XLogCtl->info_lck); newMinRecoveryPoint = XLogCtl->replayEndRecPtr; newMinRecoveryPointTLI = XLogCtl->replayEndTLI; SpinLockRelease(&XLogCtl->info_lck); if (!force && newMinRecoveryPoint < lsn) elog(WARNING, "xlog min recovery request %X/%X is past current point %X/%X", (uint32) (lsn >> 32), (uint32) lsn, (uint32) (newMinRecoveryPoint >> 32), (uint32) newMinRecoveryPoint); /* update control file */ if (ControlFile->minRecoveryPoint < newMinRecoveryPoint) { ControlFile->minRecoveryPoint = newMinRecoveryPoint; ControlFile->minRecoveryPointTLI = newMinRecoveryPointTLI; UpdateControlFile(); minRecoveryPoint = newMinRecoveryPoint; minRecoveryPointTLI = newMinRecoveryPointTLI; ereport(DEBUG2, (errmsg("updated min recovery point to %X/%X on timeline %u", (uint32) (minRecoveryPoint >> 32), (uint32) minRecoveryPoint, newMinRecoveryPointTLI))); } } LWLockRelease(ControlFileLock); } /* * Ensure that all XLOG data through the given position is flushed to disk. * * NOTE: this differs from XLogWrite mainly in that the WALWriteLock is not * already held, and we try to avoid acquiring it if possible. */ void XLogFlush(XLogRecPtr record) { XLogRecPtr WriteRqstPtr; XLogwrtRqst WriteRqst; /* * During REDO, we are reading not writing WAL. Therefore, instead of * trying to flush the WAL, we should update minRecoveryPoint instead. We * test XLogInsertAllowed(), not InRecovery, because we need checkpointer * to act this way too, and because when it tries to write the * end-of-recovery checkpoint, it should indeed flush. */ if (!XLogInsertAllowed()) { UpdateMinRecoveryPoint(record, false); return; } /* Quick exit if already known flushed */ if (record <= LogwrtResult.Flush) return; #ifdef WAL_DEBUG if (XLOG_DEBUG) elog(LOG, "xlog flush request %X/%X; write %X/%X; flush %X/%X", (uint32) (record >> 32), (uint32) record, (uint32) (LogwrtResult.Write >> 32), (uint32) LogwrtResult.Write, (uint32) (LogwrtResult.Flush >> 32), (uint32) LogwrtResult.Flush); #endif START_CRIT_SECTION(); /* * Since fsync is usually a horribly expensive operation, we try to * piggyback as much data as we can on each fsync: if we see any more data * entered into the xlog buffer, we'll write and fsync that too, so that * the final value of LogwrtResult.Flush is as large as possible. This * gives us some chance of avoiding another fsync immediately after. */ /* initialize to given target; may increase below */ WriteRqstPtr = record; /* * Now wait until we get the write lock, or someone else does the flush * for us. */ for (;;) { XLogRecPtr insertpos; /* read LogwrtResult and update local state */ SpinLockAcquire(&XLogCtl->info_lck); if (WriteRqstPtr < XLogCtl->LogwrtRqst.Write) WriteRqstPtr = XLogCtl->LogwrtRqst.Write; LogwrtResult = XLogCtl->LogwrtResult; SpinLockRelease(&XLogCtl->info_lck); /* done already? */ if (record <= LogwrtResult.Flush) break; /* * Before actually performing the write, wait for all in-flight * insertions to the pages we're about to write to finish. */ insertpos = WaitXLogInsertionsToFinish(WriteRqstPtr); /* * Try to get the write lock. If we can't get it immediately, wait * until it's released, and recheck if we still need to do the flush * or if the backend that held the lock did it for us already. This * helps to maintain a good rate of group committing when the system * is bottlenecked by the speed of fsyncing. */ if (!LWLockAcquireOrWait(WALWriteLock, LW_EXCLUSIVE)) { /* * The lock is now free, but we didn't acquire it yet. Before we * do, loop back to check if someone else flushed the record for * us already. */ continue; } /* Got the lock; recheck whether request is satisfied */ LogwrtResult = XLogCtl->LogwrtResult; if (record <= LogwrtResult.Flush) { LWLockRelease(WALWriteLock); break; } /* * Sleep before flush! By adding a delay here, we may give further * backends the opportunity to join the backlog of group commit * followers; this can significantly improve transaction throughput, * at the risk of increasing transaction latency. * * We do not sleep if enableFsync is not turned on, nor if there are * fewer than CommitSiblings other backends with active transactions. */ if (CommitDelay > 0 && enableFsync && MinimumActiveBackends(CommitSiblings)) { pg_usleep(CommitDelay); /* * Re-check how far we can now flush the WAL. It's generally not * safe to call WaitXLogInsertionsToFinish while holding * WALWriteLock, because an in-progress insertion might need to * also grab WALWriteLock to make progress. But we know that all * the insertions up to insertpos have already finished, because * that's what the earlier WaitXLogInsertionsToFinish() returned. * We're only calling it again to allow insertpos to be moved * further forward, not to actually wait for anyone. */ insertpos = WaitXLogInsertionsToFinish(insertpos); } /* try to write/flush later additions to XLOG as well */ WriteRqst.Write = insertpos; WriteRqst.Flush = insertpos; XLogWrite(WriteRqst, false); LWLockRelease(WALWriteLock); /* done */ break; } END_CRIT_SECTION(); /* wake up walsenders now that we've released heavily contended locks */ WalSndWakeupProcessRequests(); /* * If we still haven't flushed to the request point then we have a * problem; most likely, the requested flush point is past end of XLOG. * This has been seen to occur when a disk page has a corrupted LSN. * * Formerly we treated this as a PANIC condition, but that hurts the * system's robustness rather than helping it: we do not want to take down * the whole system due to corruption on one data page. In particular, if * the bad page is encountered again during recovery then we would be * unable to restart the database at all! (This scenario actually * happened in the field several times with 7.1 releases.) As of 8.4, bad * LSNs encountered during recovery are UpdateMinRecoveryPoint's problem; * the only time we can reach here during recovery is while flushing the * end-of-recovery checkpoint record, and we don't expect that to have a * bad LSN. * * Note that for calls from xact.c, the ERROR will be promoted to PANIC * since xact.c calls this routine inside a critical section. However, * calls from bufmgr.c are not within critical sections and so we will not * force a restart for a bad LSN on a data page. */ if (LogwrtResult.Flush < record) elog(ERROR, "xlog flush request %X/%X is not satisfied --- flushed only to %X/%X", (uint32) (record >> 32), (uint32) record, (uint32) (LogwrtResult.Flush >> 32), (uint32) LogwrtResult.Flush); } /* * Write & flush xlog, but without specifying exactly where to. * * We normally write only completed blocks; but if there is nothing to do on * that basis, we check for unwritten async commits in the current incomplete * block, and write through the latest one of those. Thus, if async commits * are not being used, we will write complete blocks only. * * If, based on the above, there's anything to write we do so immediately. But * to avoid calling fsync, fdatasync et. al. at a rate that'd impact * concurrent IO, we only flush WAL every wal_writer_delay ms, or if there's * more than wal_writer_flush_after unflushed blocks. * * We can guarantee that async commits reach disk after at most three * wal_writer_delay cycles. (When flushing complete blocks, we allow XLogWrite * to write "flexibly", meaning it can stop at the end of the buffer ring; * this makes a difference only with very high load or long wal_writer_delay, * but imposes one extra cycle for the worst case for async commits.) * * This routine is invoked periodically by the background walwriter process. * * Returns true if there was any work to do, even if we skipped flushing due * to wal_writer_delay/wal_writer_flush_after. */ bool XLogBackgroundFlush(void) { XLogwrtRqst WriteRqst; bool flexible = true; static TimestampTz lastflush; TimestampTz now; int flushbytes; /* XLOG doesn't need flushing during recovery */ if (RecoveryInProgress()) return false; /* read LogwrtResult and update local state */ SpinLockAcquire(&XLogCtl->info_lck); LogwrtResult = XLogCtl->LogwrtResult; WriteRqst = XLogCtl->LogwrtRqst; SpinLockRelease(&XLogCtl->info_lck); /* back off to last completed page boundary */ WriteRqst.Write -= WriteRqst.Write % XLOG_BLCKSZ; /* if we have already flushed that far, consider async commit records */ if (WriteRqst.Write <= LogwrtResult.Flush) { SpinLockAcquire(&XLogCtl->info_lck); WriteRqst.Write = XLogCtl->asyncXactLSN; SpinLockRelease(&XLogCtl->info_lck); flexible = false; /* ensure it all gets written */ } /* * If already known flushed, we're done. Just need to check if we are * holding an open file handle to a logfile that's no longer in use, * preventing the file from being deleted. */ if (WriteRqst.Write <= LogwrtResult.Flush) { if (openLogFile >= 0) { if (!XLByteInPrevSeg(LogwrtResult.Write, openLogSegNo, wal_segment_size)) { XLogFileClose(); } } return false; } /* * Determine how far to flush WAL, based on the wal_writer_delay and * wal_writer_flush_after GUCs. */ now = GetCurrentTimestamp(); flushbytes = WriteRqst.Write / XLOG_BLCKSZ - LogwrtResult.Flush / XLOG_BLCKSZ; if (WalWriterFlushAfter == 0 || lastflush == 0) { /* first call, or block based limits disabled */ WriteRqst.Flush = WriteRqst.Write; lastflush = now; } else if (TimestampDifferenceExceeds(lastflush, now, WalWriterDelay)) { /* * Flush the writes at least every WalWriterDelay ms. This is * important to bound the amount of time it takes for an asynchronous * commit to hit disk. */ WriteRqst.Flush = WriteRqst.Write; lastflush = now; } else if (flushbytes >= WalWriterFlushAfter) { /* exceeded wal_writer_flush_after blocks, flush */ WriteRqst.Flush = WriteRqst.Write; lastflush = now; } else { /* no flushing, this time round */ WriteRqst.Flush = 0; } #ifdef WAL_DEBUG if (XLOG_DEBUG) elog(LOG, "xlog bg flush request write %X/%X; flush: %X/%X, current is write %X/%X; flush %X/%X", (uint32) (WriteRqst.Write >> 32), (uint32) WriteRqst.Write, (uint32) (WriteRqst.Flush >> 32), (uint32) WriteRqst.Flush, (uint32) (LogwrtResult.Write >> 32), (uint32) LogwrtResult.Write, (uint32) (LogwrtResult.Flush >> 32), (uint32) LogwrtResult.Flush); #endif START_CRIT_SECTION(); /* now wait for any in-progress insertions to finish and get write lock */ WaitXLogInsertionsToFinish(WriteRqst.Write); LWLockAcquire(WALWriteLock, LW_EXCLUSIVE); LogwrtResult = XLogCtl->LogwrtResult; if (WriteRqst.Write > LogwrtResult.Write || WriteRqst.Flush > LogwrtResult.Flush) { XLogWrite(WriteRqst, flexible); } LWLockRelease(WALWriteLock); END_CRIT_SECTION(); /* wake up walsenders now that we've released heavily contended locks */ WalSndWakeupProcessRequests(); /* * Great, done. To take some work off the critical path, try to initialize * as many of the no-longer-needed WAL buffers for future use as we can. */ AdvanceXLInsertBuffer(InvalidXLogRecPtr, true); /* * If we determined that we need to write data, but somebody else * wrote/flushed already, it should be considered as being active, to * avoid hibernating too early. */ return true; } /* * Test whether XLOG data has been flushed up to (at least) the given position. * * Returns true if a flush is still needed. (It may be that someone else * is already in process of flushing that far, however.) */ bool XLogNeedsFlush(XLogRecPtr record) { /* * During recovery, we don't flush WAL but update minRecoveryPoint * instead. So "needs flush" is taken to mean whether minRecoveryPoint * would need to be updated. */ if (RecoveryInProgress()) { /* * An invalid minRecoveryPoint means that we need to recover all the * WAL, i.e., we're doing crash recovery. We never modify the control * file's value in that case, so we can short-circuit future checks * here too. This triggers a quick exit path for the startup process, * which cannot update its local copy of minRecoveryPoint as long as * it has not replayed all WAL available when doing crash recovery. */ if (XLogRecPtrIsInvalid(minRecoveryPoint) && InRecovery) updateMinRecoveryPoint = false; /* Quick exit if already known to be updated or cannot be updated */ if (record <= minRecoveryPoint || !updateMinRecoveryPoint) return false; /* * Update local copy of minRecoveryPoint. But if the lock is busy, * just return a conservative guess. */ if (!LWLockConditionalAcquire(ControlFileLock, LW_SHARED)) return true; minRecoveryPoint = ControlFile->minRecoveryPoint; minRecoveryPointTLI = ControlFile->minRecoveryPointTLI; LWLockRelease(ControlFileLock); /* * Check minRecoveryPoint for any other process than the startup * process doing crash recovery, which should not update the control * file value if crash recovery is still running. */ if (XLogRecPtrIsInvalid(minRecoveryPoint)) updateMinRecoveryPoint = false; /* check again */ if (record <= minRecoveryPoint || !updateMinRecoveryPoint) return false; else return true; } /* Quick exit if already known flushed */ if (record <= LogwrtResult.Flush) return false; /* read LogwrtResult and update local state */ SpinLockAcquire(&XLogCtl->info_lck); LogwrtResult = XLogCtl->LogwrtResult; SpinLockRelease(&XLogCtl->info_lck); /* check again */ if (record <= LogwrtResult.Flush) return false; return true; } /* * Create a new XLOG file segment, or open a pre-existing one. * * logsegno: identify segment to be created/opened. * * *use_existent: if true, OK to use a pre-existing file (else, any * pre-existing file will be deleted). On return, true if a pre-existing * file was used. * * use_lock: if true, acquire ControlFileLock while moving file into * place. This should be true except during bootstrap log creation. The * caller must *not* hold the lock at call. * * Returns FD of opened file. * * Note: errors here are ERROR not PANIC because we might or might not be * inside a critical section (eg, during checkpoint there is no reason to * take down the system on failure). They will promote to PANIC if we are * in a critical section. */ int XLogFileInit(XLogSegNo logsegno, bool *use_existent, bool use_lock) { char path[MAXPGPATH]; char tmppath[MAXPGPATH]; PGAlignedXLogBlock zbuffer; XLogSegNo installed_segno; XLogSegNo max_segno; int fd; int nbytes; int save_errno; XLogFilePath(path, ThisTimeLineID, logsegno, wal_segment_size); /* * Try to use existent file (checkpoint maker may have created it already) */ if (*use_existent) { fd = BasicOpenFile(path, O_RDWR | PG_BINARY | get_sync_bit(sync_method)); if (fd < 0) { if (errno != ENOENT) ereport(ERROR, (errcode_for_file_access(), errmsg("could not open file \"%s\": %m", path))); } else return fd; } /* * Initialize an empty (all zeroes) segment. NOTE: it is possible that * another process is doing the same thing. If so, we will end up * pre-creating an extra log segment. That seems OK, and better than * holding the lock throughout this lengthy process. */ elog(DEBUG2, "creating and filling new WAL file"); snprintf(tmppath, MAXPGPATH, XLOGDIR "/xlogtemp.%d", (int) getpid()); unlink(tmppath); /* do not use get_sync_bit() here --- want to fsync only at end of fill */ fd = BasicOpenFile(tmppath, O_RDWR | O_CREAT | O_EXCL | PG_BINARY); if (fd < 0) ereport(ERROR, (errcode_for_file_access(), errmsg("could not create file \"%s\": %m", tmppath))); memset(zbuffer.data, 0, XLOG_BLCKSZ); pgstat_report_wait_start(WAIT_EVENT_WAL_INIT_WRITE); save_errno = 0; if (wal_init_zero) { /* * Zero-fill the file. With this setting, we do this the hard way to * ensure that all the file space has really been allocated. On * platforms that allow "holes" in files, just seeking to the end * doesn't allocate intermediate space. This way, we know that we * have all the space and (after the fsync below) that all the * indirect blocks are down on disk. Therefore, fdatasync(2) or * O_DSYNC will be sufficient to sync future writes to the log file. */ for (nbytes = 0; nbytes < wal_segment_size; nbytes += XLOG_BLCKSZ) { errno = 0; if (write(fd, zbuffer.data, XLOG_BLCKSZ) != XLOG_BLCKSZ) { /* if write didn't set errno, assume no disk space */ save_errno = errno ? errno : ENOSPC; break; } } } else { /* * Otherwise, seeking to the end and writing a solitary byte is * enough. */ errno = 0; if (pg_pwrite(fd, zbuffer.data, 1, wal_segment_size - 1) != 1) { /* if write didn't set errno, assume no disk space */ save_errno = errno ? errno : ENOSPC; } } pgstat_report_wait_end(); if (save_errno) { /* * If we fail to make the file, delete it to release disk space */ unlink(tmppath); close(fd); errno = save_errno; ereport(ERROR, (errcode_for_file_access(), errmsg("could not write to file \"%s\": %m", tmppath))); } pgstat_report_wait_start(WAIT_EVENT_WAL_INIT_SYNC); if (pg_fsync(fd) != 0) { int save_errno = errno; close(fd); errno = save_errno; ereport(ERROR, (errcode_for_file_access(), errmsg("could not fsync file \"%s\": %m", tmppath))); } pgstat_report_wait_end(); if (close(fd) != 0) ereport(ERROR, (errcode_for_file_access(), errmsg("could not close file \"%s\": %m", tmppath))); /* * Now move the segment into place with its final name. * * If caller didn't want to use a pre-existing file, get rid of any * pre-existing file. Otherwise, cope with possibility that someone else * has created the file while we were filling ours: if so, use ours to * pre-create a future log segment. */ installed_segno = logsegno; /* * XXX: What should we use as max_segno? We used to use XLOGfileslop when * that was a constant, but that was always a bit dubious: normally, at a * checkpoint, XLOGfileslop was the offset from the checkpoint record, but * here, it was the offset from the insert location. We can't do the * normal XLOGfileslop calculation here because we don't have access to * the prior checkpoint's redo location. So somewhat arbitrarily, just use * CheckPointSegments. */ max_segno = logsegno + CheckPointSegments; if (!InstallXLogFileSegment(&installed_segno, tmppath, *use_existent, max_segno, use_lock)) { /* * No need for any more future segments, or InstallXLogFileSegment() * failed to rename the file into place. If the rename failed, opening * the file below will fail. */ unlink(tmppath); } /* Set flag to tell caller there was no existent file */ *use_existent = false; /* Now open original target segment (might not be file I just made) */ fd = BasicOpenFile(path, O_RDWR | PG_BINARY | get_sync_bit(sync_method)); if (fd < 0) ereport(ERROR, (errcode_for_file_access(), errmsg("could not open file \"%s\": %m", path))); elog(DEBUG2, "done creating and filling new WAL file"); return fd; } /* * Create a new XLOG file segment by copying a pre-existing one. * * destsegno: identify segment to be created. * * srcTLI, srcsegno: identify segment to be copied (could be from * a different timeline) * * upto: how much of the source file to copy (the rest is filled with * zeros) * * Currently this is only used during recovery, and so there are no locking * considerations. But we should be just as tense as XLogFileInit to avoid * emplacing a bogus file. */ static void XLogFileCopy(XLogSegNo destsegno, TimeLineID srcTLI, XLogSegNo srcsegno, int upto) { char path[MAXPGPATH]; char tmppath[MAXPGPATH]; PGAlignedXLogBlock buffer; int srcfd; int fd; int nbytes; /* * Open the source file */ XLogFilePath(path, srcTLI, srcsegno, wal_segment_size); srcfd = OpenTransientFile(path, O_RDONLY | PG_BINARY); if (srcfd < 0) ereport(ERROR, (errcode_for_file_access(), errmsg("could not open file \"%s\": %m", path))); /* * Copy into a temp file name. */ snprintf(tmppath, MAXPGPATH, XLOGDIR "/xlogtemp.%d", (int) getpid()); unlink(tmppath); /* do not use get_sync_bit() here --- want to fsync only at end of fill */ fd = OpenTransientFile(tmppath, O_RDWR | O_CREAT | O_EXCL | PG_BINARY); if (fd < 0) ereport(ERROR, (errcode_for_file_access(), errmsg("could not create file \"%s\": %m", tmppath))); /* * Do the data copying. */ for (nbytes = 0; nbytes < wal_segment_size; nbytes += sizeof(buffer)) { int nread; nread = upto - nbytes; /* * The part that is not read from the source file is filled with * zeros. */ if (nread < sizeof(buffer)) memset(buffer.data, 0, sizeof(buffer)); if (nread > 0) { int r; if (nread > sizeof(buffer)) nread = sizeof(buffer); pgstat_report_wait_start(WAIT_EVENT_WAL_COPY_READ); r = read(srcfd, buffer.data, nread); if (r != nread) { if (r < 0) ereport(ERROR, (errcode_for_file_access(), errmsg("could not read file \"%s\": %m", path))); else ereport(ERROR, (errcode(ERRCODE_DATA_CORRUPTED), errmsg("could not read file \"%s\": read %d of %zu", path, r, (Size) nread))); } pgstat_report_wait_end(); } errno = 0; pgstat_report_wait_start(WAIT_EVENT_WAL_COPY_WRITE); if ((int) write(fd, buffer.data, sizeof(buffer)) != (int) sizeof(buffer)) { int save_errno = errno; /* * If we fail to make the file, delete it to release disk space */ unlink(tmppath); /* if write didn't set errno, assume problem is no disk space */ errno = save_errno ? save_errno : ENOSPC; ereport(ERROR, (errcode_for_file_access(), errmsg("could not write to file \"%s\": %m", tmppath))); } pgstat_report_wait_end(); } pgstat_report_wait_start(WAIT_EVENT_WAL_COPY_SYNC); if (pg_fsync(fd) != 0) ereport(data_sync_elevel(ERROR), (errcode_for_file_access(), errmsg("could not fsync file \"%s\": %m", tmppath))); pgstat_report_wait_end(); if (CloseTransientFile(fd) != 0) ereport(ERROR, (errcode_for_file_access(), errmsg("could not close file \"%s\": %m", tmppath))); if (CloseTransientFile(srcfd) != 0) ereport(ERROR, (errcode_for_file_access(), errmsg("could not close file \"%s\": %m", path))); /* * Now move the segment into place with its final name. */ if (!InstallXLogFileSegment(&destsegno, tmppath, false, 0, false)) elog(ERROR, "InstallXLogFileSegment should not have failed"); } /* * Install a new XLOG segment file as a current or future log segment. * * This is used both to install a newly-created segment (which has a temp * filename while it's being created) and to recycle an old segment. * * *segno: identify segment to install as (or first possible target). * When find_free is true, this is modified on return to indicate the * actual installation location or last segment searched. * * tmppath: initial name of file to install. It will be renamed into place. * * find_free: if true, install the new segment at the first empty segno * number at or after the passed numbers. If false, install the new segment * exactly where specified, deleting any existing segment file there. * * max_segno: maximum segment number to install the new file as. Fail if no * free slot is found between *segno and max_segno. (Ignored when find_free * is false.) * * use_lock: if true, acquire ControlFileLock while moving file into * place. This should be true except during bootstrap log creation. The * caller must *not* hold the lock at call. * * Returns true if the file was installed successfully. false indicates that * max_segno limit was exceeded, or an error occurred while renaming the * file into place. */ static bool InstallXLogFileSegment(XLogSegNo *segno, char *tmppath, bool find_free, XLogSegNo max_segno, bool use_lock) { char path[MAXPGPATH]; struct stat stat_buf; XLogFilePath(path, ThisTimeLineID, *segno, wal_segment_size); /* * We want to be sure that only one process does this at a time. */ if (use_lock) LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); if (!find_free) { /* Force installation: get rid of any pre-existing segment file */ durable_unlink(path, DEBUG1); } else { /* Find a free slot to put it in */ while (stat(path, &stat_buf) == 0) { if ((*segno) >= max_segno) { /* Failed to find a free slot within specified range */ if (use_lock) LWLockRelease(ControlFileLock); return false; } (*segno)++; XLogFilePath(path, ThisTimeLineID, *segno, wal_segment_size); } } /* * Perform the rename using link if available, paranoidly trying to avoid * overwriting an existing file (there shouldn't be one). */ if (durable_link_or_rename(tmppath, path, LOG) != 0) { if (use_lock) LWLockRelease(ControlFileLock); /* durable_link_or_rename already emitted log message */ return false; } if (use_lock) LWLockRelease(ControlFileLock); return true; } /* * Open a pre-existing logfile segment for writing. */ int XLogFileOpen(XLogSegNo segno) { char path[MAXPGPATH]; int fd; XLogFilePath(path, ThisTimeLineID, segno, wal_segment_size); fd = BasicOpenFile(path, O_RDWR | PG_BINARY | get_sync_bit(sync_method)); if (fd < 0) ereport(PANIC, (errcode_for_file_access(), errmsg("could not open file \"%s\": %m", path))); return fd; } /* * Open a logfile segment for reading (during recovery). * * If source == XLOG_FROM_ARCHIVE, the segment is retrieved from archive. * Otherwise, it's assumed to be already available in pg_wal. */ static int XLogFileRead(XLogSegNo segno, int emode, TimeLineID tli, int source, bool notfoundOk) { char xlogfname[MAXFNAMELEN]; char activitymsg[MAXFNAMELEN + 16]; char path[MAXPGPATH]; int fd; XLogFileName(xlogfname, tli, segno, wal_segment_size); switch (source) { case XLOG_FROM_ARCHIVE: /* Report recovery progress in PS display */ snprintf(activitymsg, sizeof(activitymsg), "waiting for %s", xlogfname); set_ps_display(activitymsg, false); restoredFromArchive = RestoreArchivedFile(path, xlogfname, "RECOVERYXLOG", wal_segment_size, InRedo); if (!restoredFromArchive) return -1; break; case XLOG_FROM_PG_WAL: case XLOG_FROM_STREAM: XLogFilePath(path, tli, segno, wal_segment_size); restoredFromArchive = false; break; default: elog(ERROR, "invalid XLogFileRead source %d", source); } /* * If the segment was fetched from archival storage, replace the existing * xlog segment (if any) with the archival version. */ if (source == XLOG_FROM_ARCHIVE) { KeepFileRestoredFromArchive(path, xlogfname); /* * Set path to point at the new file in pg_wal. */ snprintf(path, MAXPGPATH, XLOGDIR "/%s", xlogfname); } fd = BasicOpenFile(path, O_RDONLY | PG_BINARY); if (fd >= 0) { /* Success! */ curFileTLI = tli; /* Report recovery progress in PS display */ snprintf(activitymsg, sizeof(activitymsg), "recovering %s", xlogfname); set_ps_display(activitymsg, false); /* Track source of data in assorted state variables */ readSource = source; XLogReceiptSource = source; /* In FROM_STREAM case, caller tracks receipt time, not me */ if (source != XLOG_FROM_STREAM) XLogReceiptTime = GetCurrentTimestamp(); return fd; } if (errno != ENOENT || !notfoundOk) /* unexpected failure? */ ereport(PANIC, (errcode_for_file_access(), errmsg("could not open file \"%s\": %m", path))); return -1; } /* * Open a logfile segment for reading (during recovery). * * This version searches for the segment with any TLI listed in expectedTLEs. */ static int XLogFileReadAnyTLI(XLogSegNo segno, int emode, int source) { char path[MAXPGPATH]; ListCell *cell; int fd; List *tles; /* * Loop looking for a suitable timeline ID: we might need to read any of * the timelines listed in expectedTLEs. * * We expect curFileTLI on entry to be the TLI of the preceding file in * sequence, or 0 if there was no predecessor. We do not allow curFileTLI * to go backwards; this prevents us from picking up the wrong file when a * parent timeline extends to higher segment numbers than the child we * want to read. * * If we haven't read the timeline history file yet, read it now, so that * we know which TLIs to scan. We don't save the list in expectedTLEs, * however, unless we actually find a valid segment. That way if there is * neither a timeline history file nor a WAL segment in the archive, and * streaming replication is set up, we'll read the timeline history file * streamed from the master when we start streaming, instead of recovering * with a dummy history generated here. */ if (expectedTLEs) tles = expectedTLEs; else tles = readTimeLineHistory(recoveryTargetTLI); foreach(cell, tles) { TimeLineID tli = ((TimeLineHistoryEntry *) lfirst(cell))->tli; if (tli < curFileTLI) break; /* don't bother looking at too-old TLIs */ if (source == XLOG_FROM_ANY || source == XLOG_FROM_ARCHIVE) { fd = XLogFileRead(segno, emode, tli, XLOG_FROM_ARCHIVE, true); if (fd != -1) { elog(DEBUG1, "got WAL segment from archive"); if (!expectedTLEs) expectedTLEs = tles; return fd; } } if (source == XLOG_FROM_ANY || source == XLOG_FROM_PG_WAL) { fd = XLogFileRead(segno, emode, tli, XLOG_FROM_PG_WAL, true); if (fd != -1) { if (!expectedTLEs) expectedTLEs = tles; return fd; } } } /* Couldn't find it. For simplicity, complain about front timeline */ XLogFilePath(path, recoveryTargetTLI, segno, wal_segment_size); errno = ENOENT; ereport(emode, (errcode_for_file_access(), errmsg("could not open file \"%s\": %m", path))); return -1; } /* * Close the current logfile segment for writing. */ static void XLogFileClose(void) { Assert(openLogFile >= 0); /* * WAL segment files will not be re-read in normal operation, so we advise * the OS to release any cached pages. But do not do so if WAL archiving * or streaming is active, because archiver and walsender process could * use the cache to read the WAL segment. */ #if defined(USE_POSIX_FADVISE) && defined(POSIX_FADV_DONTNEED) if (!XLogIsNeeded()) (void) posix_fadvise(openLogFile, 0, 0, POSIX_FADV_DONTNEED); #endif if (close(openLogFile) != 0) { char xlogfname[MAXFNAMELEN]; int save_errno = errno; XLogFileName(xlogfname, ThisTimeLineID, openLogSegNo, wal_segment_size); errno = save_errno; ereport(PANIC, (errcode_for_file_access(), errmsg("could not close file \"%s\": %m", xlogfname))); } openLogFile = -1; } /* * Preallocate log files beyond the specified log endpoint. * * XXX this is currently extremely conservative, since it forces only one * future log segment to exist, and even that only if we are 75% done with * the current one. This is only appropriate for very low-WAL-volume systems. * High-volume systems will be OK once they've built up a sufficient set of * recycled log segments, but the startup transient is likely to include * a lot of segment creations by foreground processes, which is not so good. */ static void PreallocXlogFiles(XLogRecPtr endptr) { XLogSegNo _logSegNo; int lf; bool use_existent; uint64 offset; XLByteToPrevSeg(endptr, _logSegNo, wal_segment_size); offset = XLogSegmentOffset(endptr - 1, wal_segment_size); if (offset >= (uint32) (0.75 * wal_segment_size)) { _logSegNo++; use_existent = true; lf = XLogFileInit(_logSegNo, &use_existent, true); close(lf); if (!use_existent) CheckpointStats.ckpt_segs_added++; } } /* * Throws an error if the given log segment has already been removed or * recycled. The caller should only pass a segment that it knows to have * existed while the server has been running, as this function always * succeeds if no WAL segments have been removed since startup. * 'tli' is only used in the error message. * * Note: this function guarantees to keep errno unchanged on return. * This supports callers that use this to possibly deliver a better * error message about a missing file, while still being able to throw * a normal file-access error afterwards, if this does return. */ void CheckXLogRemoved(XLogSegNo segno, TimeLineID tli) { int save_errno = errno; XLogSegNo lastRemovedSegNo; SpinLockAcquire(&XLogCtl->info_lck); lastRemovedSegNo = XLogCtl->lastRemovedSegNo; SpinLockRelease(&XLogCtl->info_lck); if (segno <= lastRemovedSegNo) { char filename[MAXFNAMELEN]; XLogFileName(filename, tli, segno, wal_segment_size); errno = save_errno; ereport(ERROR, (errcode_for_file_access(), errmsg("requested WAL segment %s has already been removed", filename))); } errno = save_errno; } /* * Return the last WAL segment removed, or 0 if no segment has been removed * since startup. * * NB: the result can be out of date arbitrarily fast, the caller has to deal * with that. */ XLogSegNo XLogGetLastRemovedSegno(void) { XLogSegNo lastRemovedSegNo; SpinLockAcquire(&XLogCtl->info_lck); lastRemovedSegNo = XLogCtl->lastRemovedSegNo; SpinLockRelease(&XLogCtl->info_lck); return lastRemovedSegNo; } /* * Update the last removed segno pointer in shared memory, to reflect * that the given XLOG file has been removed. */ static void UpdateLastRemovedPtr(char *filename) { uint32 tli; XLogSegNo segno; XLogFromFileName(filename, &tli, &segno, wal_segment_size); SpinLockAcquire(&XLogCtl->info_lck); if (segno > XLogCtl->lastRemovedSegNo) XLogCtl->lastRemovedSegNo = segno; SpinLockRelease(&XLogCtl->info_lck); } /* * Remove all temporary log files in pg_wal * * This is called at the beginning of recovery after a previous crash, * at a point where no other processes write fresh WAL data. */ static void RemoveTempXlogFiles(void) { DIR *xldir; struct dirent *xlde; elog(DEBUG2, "removing all temporary WAL segments"); xldir = AllocateDir(XLOGDIR); while ((xlde = ReadDir(xldir, XLOGDIR)) != NULL) { char path[MAXPGPATH]; if (strncmp(xlde->d_name, "xlogtemp.", 9) != 0) continue; snprintf(path, MAXPGPATH, XLOGDIR "/%s", xlde->d_name); unlink(path); elog(DEBUG2, "removed temporary WAL segment \"%s\"", path); } FreeDir(xldir); } /* * Recycle or remove all log files older or equal to passed segno. * * endptr is current (or recent) end of xlog, and lastredoptr is the * redo pointer of the last checkpoint. These are used to determine * whether we want to recycle rather than delete no-longer-wanted log files. */ static void RemoveOldXlogFiles(XLogSegNo segno, XLogRecPtr lastredoptr, XLogRecPtr endptr) { DIR *xldir; struct dirent *xlde; char lastoff[MAXFNAMELEN]; /* * Construct a filename of the last segment to be kept. The timeline ID * doesn't matter, we ignore that in the comparison. (During recovery, * ThisTimeLineID isn't set, so we can't use that.) */ XLogFileName(lastoff, 0, segno, wal_segment_size); elog(DEBUG2, "attempting to remove WAL segments older than log file %s", lastoff); xldir = AllocateDir(XLOGDIR); while ((xlde = ReadDir(xldir, XLOGDIR)) != NULL) { /* Ignore files that are not XLOG segments */ if (!IsXLogFileName(xlde->d_name) && !IsPartialXLogFileName(xlde->d_name)) continue; /* * We ignore the timeline part of the XLOG segment identifiers in * deciding whether a segment is still needed. This ensures that we * won't prematurely remove a segment from a parent timeline. We could * probably be a little more proactive about removing segments of * non-parent timelines, but that would be a whole lot more * complicated. * * We use the alphanumeric sorting property of the filenames to decide * which ones are earlier than the lastoff segment. */ if (strcmp(xlde->d_name + 8, lastoff + 8) <= 0) { if (XLogArchiveCheckDone(xlde->d_name)) { /* Update the last removed location in shared memory first */ UpdateLastRemovedPtr(xlde->d_name); RemoveXlogFile(xlde->d_name, lastredoptr, endptr); } } } FreeDir(xldir); } /* * Remove WAL files that are not part of the given timeline's history. * * This is called during recovery, whenever we switch to follow a new * timeline, and at the end of recovery when we create a new timeline. We * wouldn't otherwise care about extra WAL files lying in pg_wal, but they * might be leftover pre-allocated or recycled WAL segments on the old timeline * that we haven't used yet, and contain garbage. If we just leave them in * pg_wal, they will eventually be archived, and we can't let that happen. * Files that belong to our timeline history are valid, because we have * successfully replayed them, but from others we can't be sure. * * 'switchpoint' is the current point in WAL where we switch to new timeline, * and 'newTLI' is the new timeline we switch to. */ static void RemoveNonParentXlogFiles(XLogRecPtr switchpoint, TimeLineID newTLI) { DIR *xldir; struct dirent *xlde; char switchseg[MAXFNAMELEN]; XLogSegNo endLogSegNo; XLByteToPrevSeg(switchpoint, endLogSegNo, wal_segment_size); /* * Construct a filename of the last segment to be kept. */ XLogFileName(switchseg, newTLI, endLogSegNo, wal_segment_size); elog(DEBUG2, "attempting to remove WAL segments newer than log file %s", switchseg); xldir = AllocateDir(XLOGDIR); while ((xlde = ReadDir(xldir, XLOGDIR)) != NULL) { /* Ignore files that are not XLOG segments */ if (!IsXLogFileName(xlde->d_name)) continue; /* * Remove files that are on a timeline older than the new one we're * switching to, but with a segment number >= the first segment on the * new timeline. */ if (strncmp(xlde->d_name, switchseg, 8) < 0 && strcmp(xlde->d_name + 8, switchseg + 8) > 0) { /* * If the file has already been marked as .ready, however, don't * remove it yet. It should be OK to remove it - files that are * not part of our timeline history are not required for recovery * - but seems safer to let them be archived and removed later. */ if (!XLogArchiveIsReady(xlde->d_name)) RemoveXlogFile(xlde->d_name, InvalidXLogRecPtr, switchpoint); } } FreeDir(xldir); } /* * Recycle or remove a log file that's no longer needed. * * endptr is current (or recent) end of xlog, and lastredoptr is the * redo pointer of the last checkpoint. These are used to determine * whether we want to recycle rather than delete no-longer-wanted log files. * If lastredoptr is not known, pass invalid, and the function will recycle, * somewhat arbitrarily, 10 future segments. */ static void RemoveXlogFile(const char *segname, XLogRecPtr lastredoptr, XLogRecPtr endptr) { char path[MAXPGPATH]; #ifdef WIN32 char newpath[MAXPGPATH]; #endif struct stat statbuf; XLogSegNo endlogSegNo; XLogSegNo recycleSegNo; if (wal_recycle) { /* * Initialize info about where to try to recycle to. */ XLByteToSeg(endptr, endlogSegNo, wal_segment_size); if (lastredoptr == InvalidXLogRecPtr) recycleSegNo = endlogSegNo + 10; else recycleSegNo = XLOGfileslop(lastredoptr); } else recycleSegNo = 0; /* keep compiler quiet */ snprintf(path, MAXPGPATH, XLOGDIR "/%s", segname); /* * Before deleting the file, see if it can be recycled as a future log * segment. Only recycle normal files, pg_standby for example can create * symbolic links pointing to a separate archive directory. */ if (wal_recycle && endlogSegNo <= recycleSegNo && lstat(path, &statbuf) == 0 && S_ISREG(statbuf.st_mode) && InstallXLogFileSegment(&endlogSegNo, path, true, recycleSegNo, true)) { ereport(DEBUG2, (errmsg("recycled write-ahead log file \"%s\"", segname))); CheckpointStats.ckpt_segs_recycled++; /* Needn't recheck that slot on future iterations */ endlogSegNo++; } else { /* No need for any more future segments... */ int rc; ereport(DEBUG2, (errmsg("removing write-ahead log file \"%s\"", segname))); #ifdef WIN32 /* * On Windows, if another process (e.g another backend) holds the file * open in FILE_SHARE_DELETE mode, unlink will succeed, but the file * will still show up in directory listing until the last handle is * closed. To avoid confusing the lingering deleted file for a live * WAL file that needs to be archived, rename it before deleting it. * * If another process holds the file open without FILE_SHARE_DELETE * flag, rename will fail. We'll try again at the next checkpoint. */ snprintf(newpath, MAXPGPATH, "%s.deleted", path); if (rename(path, newpath) != 0) { ereport(LOG, (errcode_for_file_access(), errmsg("could not rename file \"%s\": %m", path))); return; } rc = durable_unlink(newpath, LOG); #else rc = durable_unlink(path, LOG); #endif if (rc != 0) { /* Message already logged by durable_unlink() */ return; } CheckpointStats.ckpt_segs_removed++; } XLogArchiveCleanup(segname); } /* * Verify whether pg_wal and pg_wal/archive_status exist. * If the latter does not exist, recreate it. * * It is not the goal of this function to verify the contents of these * directories, but to help in cases where someone has performed a cluster * copy for PITR purposes but omitted pg_wal from the copy. * * We could also recreate pg_wal if it doesn't exist, but a deliberate * policy decision was made not to. It is fairly common for pg_wal to be * a symlink, and if that was the DBA's intent then automatically making a * plain directory would result in degraded performance with no notice. */ static void ValidateXLOGDirectoryStructure(void) { char path[MAXPGPATH]; struct stat stat_buf; /* Check for pg_wal; if it doesn't exist, error out */ if (stat(XLOGDIR, &stat_buf) != 0 || !S_ISDIR(stat_buf.st_mode)) ereport(FATAL, (errmsg("required WAL directory \"%s\" does not exist", XLOGDIR))); /* Check for archive_status */ snprintf(path, MAXPGPATH, XLOGDIR "/archive_status"); if (stat(path, &stat_buf) == 0) { /* Check for weird cases where it exists but isn't a directory */ if (!S_ISDIR(stat_buf.st_mode)) ereport(FATAL, (errmsg("required WAL directory \"%s\" does not exist", path))); } else { ereport(LOG, (errmsg("creating missing WAL directory \"%s\"", path))); if (MakePGDirectory(path) < 0) ereport(FATAL, (errmsg("could not create missing directory \"%s\": %m", path))); } } /* * Remove previous backup history files. This also retries creation of * .ready files for any backup history files for which XLogArchiveNotify * failed earlier. */ static void CleanupBackupHistory(void) { DIR *xldir; struct dirent *xlde; char path[MAXPGPATH + sizeof(XLOGDIR)]; xldir = AllocateDir(XLOGDIR); while ((xlde = ReadDir(xldir, XLOGDIR)) != NULL) { if (IsBackupHistoryFileName(xlde->d_name)) { if (XLogArchiveCheckDone(xlde->d_name)) { elog(DEBUG2, "removing WAL backup history file \"%s\"", xlde->d_name); snprintf(path, sizeof(path), XLOGDIR "/%s", xlde->d_name); unlink(path); XLogArchiveCleanup(xlde->d_name); } } } FreeDir(xldir); } /* * Attempt to read the next XLOG record. * * Before first call, the reader needs to be positioned to the first record * by calling XLogBeginRead(). * * If no valid record is available, returns NULL, or fails if emode is PANIC. * (emode must be either PANIC, LOG). In standby mode, retries until a valid * record is available. */ static XLogRecord * ReadRecord(XLogReaderState *xlogreader, int emode, bool fetching_ckpt) { XLogRecord *record; XLogPageReadPrivate *private = (XLogPageReadPrivate *) xlogreader->private_data; /* Pass through parameters to XLogPageRead */ private->fetching_ckpt = fetching_ckpt; private->emode = emode; private->randAccess = (xlogreader->ReadRecPtr != InvalidXLogRecPtr); /* This is the first attempt to read this page. */ lastSourceFailed = false; for (;;) { char *errormsg; record = XLogReadRecord(xlogreader, &errormsg); ReadRecPtr = xlogreader->ReadRecPtr; EndRecPtr = xlogreader->EndRecPtr; if (record == NULL) { if (readFile >= 0) { close(readFile); readFile = -1; } /* * We only end up here without a message when XLogPageRead() * failed - in that case we already logged something. In * StandbyMode that only happens if we have been triggered, so we * shouldn't loop anymore in that case. */ if (errormsg) ereport(emode_for_corrupt_record(emode, EndRecPtr), (errmsg_internal("%s", errormsg) /* already translated */ )); } /* * Check page TLI is one of the expected values. */ else if (!tliInHistory(xlogreader->latestPageTLI, expectedTLEs)) { char fname[MAXFNAMELEN]; XLogSegNo segno; int32 offset; XLByteToSeg(xlogreader->latestPagePtr, segno, wal_segment_size); offset = XLogSegmentOffset(xlogreader->latestPagePtr, wal_segment_size); XLogFileName(fname, xlogreader->seg.ws_tli, segno, wal_segment_size); ereport(emode_for_corrupt_record(emode, EndRecPtr), (errmsg("unexpected timeline ID %u in log segment %s, offset %u", xlogreader->latestPageTLI, fname, offset))); record = NULL; } if (record) { /* Great, got a record */ return record; } else { /* No valid record available from this source */ lastSourceFailed = true; /* * If archive recovery was requested, but we were still doing * crash recovery, switch to archive recovery and retry using the * offline archive. We have now replayed all the valid WAL in * pg_wal, so we are presumably now consistent. * * We require that there's at least some valid WAL present in * pg_wal, however (!fetching_ckpt). We could recover using the * WAL from the archive, even if pg_wal is completely empty, but * we'd have no idea how far we'd have to replay to reach * consistency. So err on the safe side and give up. */ if (!InArchiveRecovery && ArchiveRecoveryRequested && !fetching_ckpt) { ereport(DEBUG1, (errmsg_internal("reached end of WAL in pg_wal, entering archive recovery"))); InArchiveRecovery = true; if (StandbyModeRequested) StandbyMode = true; /* initialize minRecoveryPoint to this record */ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); ControlFile->state = DB_IN_ARCHIVE_RECOVERY; if (ControlFile->minRecoveryPoint < EndRecPtr) { ControlFile->minRecoveryPoint = EndRecPtr; ControlFile->minRecoveryPointTLI = ThisTimeLineID; } /* update local copy */ minRecoveryPoint = ControlFile->minRecoveryPoint; minRecoveryPointTLI = ControlFile->minRecoveryPointTLI; /* * The startup process can update its local copy of * minRecoveryPoint from this point. */ updateMinRecoveryPoint = true; UpdateControlFile(); LWLockRelease(ControlFileLock); CheckRecoveryConsistency(); /* * Before we retry, reset lastSourceFailed and currentSource * so that we will check the archive next. */ lastSourceFailed = false; currentSource = 0; continue; } /* In standby mode, loop back to retry. Otherwise, give up. */ if (StandbyMode && !CheckForStandbyTrigger()) continue; else return NULL; } } } /* * Scan for new timelines that might have appeared in the archive since we * started recovery. * * If there are any, the function changes recovery target TLI to the latest * one and returns 'true'. */ static bool rescanLatestTimeLine(void) { List *newExpectedTLEs; bool found; ListCell *cell; TimeLineID newtarget; TimeLineID oldtarget = recoveryTargetTLI; TimeLineHistoryEntry *currentTle = NULL; newtarget = findNewestTimeLine(recoveryTargetTLI); if (newtarget == recoveryTargetTLI) { /* No new timelines found */ return false; } /* * Determine the list of expected TLIs for the new TLI */ newExpectedTLEs = readTimeLineHistory(newtarget); /* * If the current timeline is not part of the history of the new timeline, * we cannot proceed to it. */ found = false; foreach(cell, newExpectedTLEs) { currentTle = (TimeLineHistoryEntry *) lfirst(cell); if (currentTle->tli == recoveryTargetTLI) { found = true; break; } } if (!found) { ereport(LOG, (errmsg("new timeline %u is not a child of database system timeline %u", newtarget, ThisTimeLineID))); return false; } /* * The current timeline was found in the history file, but check that the * next timeline was forked off from it *after* the current recovery * location. */ if (currentTle->end < EndRecPtr) { ereport(LOG, (errmsg("new timeline %u forked off current database system timeline %u before current recovery point %X/%X", newtarget, ThisTimeLineID, (uint32) (EndRecPtr >> 32), (uint32) EndRecPtr))); return false; } /* The new timeline history seems valid. Switch target */ recoveryTargetTLI = newtarget; list_free_deep(expectedTLEs); expectedTLEs = newExpectedTLEs; /* * As in StartupXLOG(), try to ensure we have all the history files * between the old target and new target in pg_wal. */ restoreTimeLineHistoryFiles(oldtarget + 1, newtarget); ereport(LOG, (errmsg("new target timeline is %u", recoveryTargetTLI))); return true; } /* * I/O routines for pg_control * * *ControlFile is a buffer in shared memory that holds an image of the * contents of pg_control. WriteControlFile() initializes pg_control * given a preloaded buffer, ReadControlFile() loads the buffer from * the pg_control file (during postmaster or standalone-backend startup), * and UpdateControlFile() rewrites pg_control after we modify xlog state. * * For simplicity, WriteControlFile() initializes the fields of pg_control * that are related to checking backend/database compatibility, and * ReadControlFile() verifies they are correct. We could split out the * I/O and compatibility-check functions, but there seems no need currently. */ static void WriteControlFile(void) { int fd; char buffer[PG_CONTROL_FILE_SIZE]; /* need not be aligned */ /* * Ensure that the size of the pg_control data structure is sane. See the * comments for these symbols in pg_control.h. */ StaticAssertStmt(sizeof(ControlFileData) <= PG_CONTROL_MAX_SAFE_SIZE, "pg_control is too large for atomic disk writes"); StaticAssertStmt(sizeof(ControlFileData) <= PG_CONTROL_FILE_SIZE, "sizeof(ControlFileData) exceeds PG_CONTROL_FILE_SIZE"); /* * Initialize version and compatibility-check fields */ ControlFile->pg_control_version = PG_CONTROL_VERSION; ControlFile->catalog_version_no = CATALOG_VERSION_NO; ControlFile->maxAlign = MAXIMUM_ALIGNOF; ControlFile->floatFormat = FLOATFORMAT_VALUE; ControlFile->blcksz = BLCKSZ; ControlFile->relseg_size = RELSEG_SIZE; ControlFile->xlog_blcksz = XLOG_BLCKSZ; ControlFile->xlog_seg_size = wal_segment_size; ControlFile->nameDataLen = NAMEDATALEN; ControlFile->indexMaxKeys = INDEX_MAX_KEYS; ControlFile->toast_max_chunk_size = TOAST_MAX_CHUNK_SIZE; ControlFile->loblksize = LOBLKSIZE; ControlFile->float8ByVal = FLOAT8PASSBYVAL; /* Contents are protected with a CRC */ INIT_CRC32C(ControlFile->crc); COMP_CRC32C(ControlFile->crc, (char *) ControlFile, offsetof(ControlFileData, crc)); FIN_CRC32C(ControlFile->crc); /* * We write out PG_CONTROL_FILE_SIZE bytes into pg_control, zero-padding * the excess over sizeof(ControlFileData). This reduces the odds of * premature-EOF errors when reading pg_control. We'll still fail when we * check the contents of the file, but hopefully with a more specific * error than "couldn't read pg_control". */ memset(buffer, 0, PG_CONTROL_FILE_SIZE); memcpy(buffer, ControlFile, sizeof(ControlFileData)); fd = BasicOpenFile(XLOG_CONTROL_FILE, O_RDWR | O_CREAT | O_EXCL | PG_BINARY); if (fd < 0) ereport(PANIC, (errcode_for_file_access(), errmsg("could not create file \"%s\": %m", XLOG_CONTROL_FILE))); errno = 0; pgstat_report_wait_start(WAIT_EVENT_CONTROL_FILE_WRITE); if (write(fd, buffer, PG_CONTROL_FILE_SIZE) != PG_CONTROL_FILE_SIZE) { /* if write didn't set errno, assume problem is no disk space */ if (errno == 0) errno = ENOSPC; ereport(PANIC, (errcode_for_file_access(), errmsg("could not write to file \"%s\": %m", XLOG_CONTROL_FILE))); } pgstat_report_wait_end(); pgstat_report_wait_start(WAIT_EVENT_CONTROL_FILE_SYNC); if (pg_fsync(fd) != 0) ereport(PANIC, (errcode_for_file_access(), errmsg("could not fsync file \"%s\": %m", XLOG_CONTROL_FILE))); pgstat_report_wait_end(); if (close(fd) != 0) ereport(PANIC, (errcode_for_file_access(), errmsg("could not close file \"%s\": %m", XLOG_CONTROL_FILE))); } static void ReadControlFile(void) { pg_crc32c crc; int fd; static char wal_segsz_str[20]; int r; /* * Read data... */ fd = BasicOpenFile(XLOG_CONTROL_FILE, O_RDWR | PG_BINARY); if (fd < 0) ereport(PANIC, (errcode_for_file_access(), errmsg("could not open file \"%s\": %m", XLOG_CONTROL_FILE))); pgstat_report_wait_start(WAIT_EVENT_CONTROL_FILE_READ); r = read(fd, ControlFile, sizeof(ControlFileData)); if (r != sizeof(ControlFileData)) { if (r < 0) ereport(PANIC, (errcode_for_file_access(), errmsg("could not read file \"%s\": %m", XLOG_CONTROL_FILE))); else ereport(PANIC, (errcode(ERRCODE_DATA_CORRUPTED), errmsg("could not read file \"%s\": read %d of %zu", XLOG_CONTROL_FILE, r, sizeof(ControlFileData)))); } pgstat_report_wait_end(); close(fd); /* * Check for expected pg_control format version. If this is wrong, the * CRC check will likely fail because we'll be checking the wrong number * of bytes. Complaining about wrong version will probably be more * enlightening than complaining about wrong CRC. */ if (ControlFile->pg_control_version != PG_CONTROL_VERSION && ControlFile->pg_control_version % 65536 == 0 && ControlFile->pg_control_version / 65536 != 0) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized with PG_CONTROL_VERSION %d (0x%08x)," " but the server was compiled with PG_CONTROL_VERSION %d (0x%08x).", ControlFile->pg_control_version, ControlFile->pg_control_version, PG_CONTROL_VERSION, PG_CONTROL_VERSION), errhint("This could be a problem of mismatched byte ordering. It looks like you need to initdb."))); if (ControlFile->pg_control_version != PG_CONTROL_VERSION) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized with PG_CONTROL_VERSION %d," " but the server was compiled with PG_CONTROL_VERSION %d.", ControlFile->pg_control_version, PG_CONTROL_VERSION), errhint("It looks like you need to initdb."))); /* Now check the CRC. */ INIT_CRC32C(crc); COMP_CRC32C(crc, (char *) ControlFile, offsetof(ControlFileData, crc)); FIN_CRC32C(crc); if (!EQ_CRC32C(crc, ControlFile->crc)) ereport(FATAL, (errmsg("incorrect checksum in control file"))); /* * Do compatibility checking immediately. If the database isn't * compatible with the backend executable, we want to abort before we can * possibly do any damage. */ if (ControlFile->catalog_version_no != CATALOG_VERSION_NO) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized with CATALOG_VERSION_NO %d," " but the server was compiled with CATALOG_VERSION_NO %d.", ControlFile->catalog_version_no, CATALOG_VERSION_NO), errhint("It looks like you need to initdb."))); if (ControlFile->maxAlign != MAXIMUM_ALIGNOF) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized with MAXALIGN %d," " but the server was compiled with MAXALIGN %d.", ControlFile->maxAlign, MAXIMUM_ALIGNOF), errhint("It looks like you need to initdb."))); if (ControlFile->floatFormat != FLOATFORMAT_VALUE) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster appears to use a different floating-point number format than the server executable."), errhint("It looks like you need to initdb."))); if (ControlFile->blcksz != BLCKSZ) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized with BLCKSZ %d," " but the server was compiled with BLCKSZ %d.", ControlFile->blcksz, BLCKSZ), errhint("It looks like you need to recompile or initdb."))); if (ControlFile->relseg_size != RELSEG_SIZE) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized with RELSEG_SIZE %d," " but the server was compiled with RELSEG_SIZE %d.", ControlFile->relseg_size, RELSEG_SIZE), errhint("It looks like you need to recompile or initdb."))); if (ControlFile->xlog_blcksz != XLOG_BLCKSZ) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized with XLOG_BLCKSZ %d," " but the server was compiled with XLOG_BLCKSZ %d.", ControlFile->xlog_blcksz, XLOG_BLCKSZ), errhint("It looks like you need to recompile or initdb."))); if (ControlFile->nameDataLen != NAMEDATALEN) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized with NAMEDATALEN %d," " but the server was compiled with NAMEDATALEN %d.", ControlFile->nameDataLen, NAMEDATALEN), errhint("It looks like you need to recompile or initdb."))); if (ControlFile->indexMaxKeys != INDEX_MAX_KEYS) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized with INDEX_MAX_KEYS %d," " but the server was compiled with INDEX_MAX_KEYS %d.", ControlFile->indexMaxKeys, INDEX_MAX_KEYS), errhint("It looks like you need to recompile or initdb."))); if (ControlFile->toast_max_chunk_size != TOAST_MAX_CHUNK_SIZE) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized with TOAST_MAX_CHUNK_SIZE %d," " but the server was compiled with TOAST_MAX_CHUNK_SIZE %d.", ControlFile->toast_max_chunk_size, (int) TOAST_MAX_CHUNK_SIZE), errhint("It looks like you need to recompile or initdb."))); if (ControlFile->loblksize != LOBLKSIZE) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized with LOBLKSIZE %d," " but the server was compiled with LOBLKSIZE %d.", ControlFile->loblksize, (int) LOBLKSIZE), errhint("It looks like you need to recompile or initdb."))); #ifdef USE_FLOAT8_BYVAL if (ControlFile->float8ByVal != true) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized without USE_FLOAT8_BYVAL" " but the server was compiled with USE_FLOAT8_BYVAL."), errhint("It looks like you need to recompile or initdb."))); #else if (ControlFile->float8ByVal != false) ereport(FATAL, (errmsg("database files are incompatible with server"), errdetail("The database cluster was initialized with USE_FLOAT8_BYVAL" " but the server was compiled without USE_FLOAT8_BYVAL."), errhint("It looks like you need to recompile or initdb."))); #endif wal_segment_size = ControlFile->xlog_seg_size; if (!IsValidWalSegSize(wal_segment_size)) ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE), errmsg_plural("WAL segment size must be a power of two between 1 MB and 1 GB, but the control file specifies %d byte", "WAL segment size must be a power of two between 1 MB and 1 GB, but the control file specifies %d bytes", wal_segment_size, wal_segment_size))); snprintf(wal_segsz_str, sizeof(wal_segsz_str), "%d", wal_segment_size); SetConfigOption("wal_segment_size", wal_segsz_str, PGC_INTERNAL, PGC_S_OVERRIDE); /* check and update variables dependent on wal_segment_size */ if (ConvertToXSegs(min_wal_size_mb, wal_segment_size) < 2) ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE), errmsg("\"min_wal_size\" must be at least twice \"wal_segment_size\""))); if (ConvertToXSegs(max_wal_size_mb, wal_segment_size) < 2) ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE), errmsg("\"max_wal_size\" must be at least twice \"wal_segment_size\""))); UsableBytesInSegment = (wal_segment_size / XLOG_BLCKSZ * UsableBytesInPage) - (SizeOfXLogLongPHD - SizeOfXLogShortPHD); CalculateCheckpointSegments(); /* Make the initdb settings visible as GUC variables, too */ SetConfigOption("data_checksums", DataChecksumsEnabled() ? "yes" : "no", PGC_INTERNAL, PGC_S_OVERRIDE); } /* * Utility wrapper to update the control file. Note that the control * file gets flushed. */ void UpdateControlFile(void) { update_controlfile(DataDir, ControlFile, true); } /* * Returns the unique system identifier from control file. */ uint64 GetSystemIdentifier(void) { Assert(ControlFile != NULL); return ControlFile->system_identifier; } /* * Returns the random nonce from control file. */ char * GetMockAuthenticationNonce(void) { Assert(ControlFile != NULL); return ControlFile->mock_authentication_nonce; } /* * Are checksums enabled for data pages? */ bool DataChecksumsEnabled(void) { Assert(ControlFile != NULL); return (ControlFile->data_checksum_version > 0); } /* * Returns a fake LSN for unlogged relations. * * Each call generates an LSN that is greater than any previous value * returned. The current counter value is saved and restored across clean * shutdowns, but like unlogged relations, does not survive a crash. This can * be used in lieu of real LSN values returned by XLogInsert, if you need an * LSN-like increasing sequence of numbers without writing any WAL. */ XLogRecPtr GetFakeLSNForUnloggedRel(void) { XLogRecPtr nextUnloggedLSN; /* increment the unloggedLSN counter, need SpinLock */ SpinLockAcquire(&XLogCtl->ulsn_lck); nextUnloggedLSN = XLogCtl->unloggedLSN++; SpinLockRelease(&XLogCtl->ulsn_lck); return nextUnloggedLSN; } /* * Auto-tune the number of XLOG buffers. * * The preferred setting for wal_buffers is about 3% of shared_buffers, with * a maximum of one XLOG segment (there is little reason to think that more * is helpful, at least so long as we force an fsync when switching log files) * and a minimum of 8 blocks (which was the default value prior to PostgreSQL * 9.1, when auto-tuning was added). * * This should not be called until NBuffers has received its final value. */ static int XLOGChooseNumBuffers(void) { int xbuffers; xbuffers = NBuffers / 32; if (xbuffers > (wal_segment_size / XLOG_BLCKSZ)) xbuffers = (wal_segment_size / XLOG_BLCKSZ); if (xbuffers < 8) xbuffers = 8; return xbuffers; } /* * GUC check_hook for wal_buffers */ bool check_wal_buffers(int *newval, void **extra, GucSource source) { /* * -1 indicates a request for auto-tune. */ if (*newval == -1) { /* * If we haven't yet changed the boot_val default of -1, just let it * be. We'll fix it when XLOGShmemSize is called. */ if (XLOGbuffers == -1) return true; /* Otherwise, substitute the auto-tune value */ *newval = XLOGChooseNumBuffers(); } /* * We clamp manually-set values to at least 4 blocks. Prior to PostgreSQL * 9.1, a minimum of 4 was enforced by guc.c, but since that is no longer * the case, we just silently treat such values as a request for the * minimum. (We could throw an error instead, but that doesn't seem very * helpful.) */ if (*newval < 4) *newval = 4; return true; } /* * Read the control file, set respective GUCs. * * This is to be called during startup, including a crash recovery cycle, * unless in bootstrap mode, where no control file yet exists. As there's no * usable shared memory yet (its sizing can depend on the contents of the * control file!), first store the contents in local memory. XLOGShmemInit() * will then copy it to shared memory later. * * reset just controls whether previous contents are to be expected (in the * reset case, there's a dangling pointer into old shared memory), or not. */ void LocalProcessControlFile(bool reset) { Assert(reset || ControlFile == NULL); ControlFile = palloc(sizeof(ControlFileData)); ReadControlFile(); } /* * Initialization of shared memory for XLOG */ Size XLOGShmemSize(void) { Size size; /* * If the value of wal_buffers is -1, use the preferred auto-tune value. * This isn't an amazingly clean place to do this, but we must wait till * NBuffers has received its final value, and must do it before using the * value of XLOGbuffers to do anything important. */ if (XLOGbuffers == -1) { char buf[32]; snprintf(buf, sizeof(buf), "%d", XLOGChooseNumBuffers()); SetConfigOption("wal_buffers", buf, PGC_POSTMASTER, PGC_S_OVERRIDE); } Assert(XLOGbuffers > 0); /* XLogCtl */ size = sizeof(XLogCtlData); /* WAL insertion locks, plus alignment */ size = add_size(size, mul_size(sizeof(WALInsertLockPadded), NUM_XLOGINSERT_LOCKS + 1)); /* xlblocks array */ size = add_size(size, mul_size(sizeof(XLogRecPtr), XLOGbuffers)); /* extra alignment padding for XLOG I/O buffers */ size = add_size(size, XLOG_BLCKSZ); /* and the buffers themselves */ size = add_size(size, mul_size(XLOG_BLCKSZ, XLOGbuffers)); /* * Note: we don't count ControlFileData, it comes out of the "slop factor" * added by CreateSharedMemoryAndSemaphores. This lets us use this * routine again below to compute the actual allocation size. */ return size; } void XLOGShmemInit(void) { bool foundCFile, foundXLog; char *allocptr; int i; ControlFileData *localControlFile; #ifdef WAL_DEBUG /* * Create a memory context for WAL debugging that's exempt from the normal * "no pallocs in critical section" rule. Yes, that can lead to a PANIC if * an allocation fails, but wal_debug is not for production use anyway. */ if (walDebugCxt == NULL) { walDebugCxt = AllocSetContextCreate(TopMemoryContext, "WAL Debug", ALLOCSET_DEFAULT_SIZES); MemoryContextAllowInCriticalSection(walDebugCxt, true); } #endif XLogCtl = (XLogCtlData *) ShmemInitStruct("XLOG Ctl", XLOGShmemSize(), &foundXLog); localControlFile = ControlFile; ControlFile = (ControlFileData *) ShmemInitStruct("Control File", sizeof(ControlFileData), &foundCFile); if (foundCFile || foundXLog) { /* both should be present or neither */ Assert(foundCFile && foundXLog); /* Initialize local copy of WALInsertLocks and register the tranche */ WALInsertLocks = XLogCtl->Insert.WALInsertLocks; LWLockRegisterTranche(LWTRANCHE_WAL_INSERT, "wal_insert"); if (localControlFile) pfree(localControlFile); return; } memset(XLogCtl, 0, sizeof(XLogCtlData)); /* * Already have read control file locally, unless in bootstrap mode. Move * contents into shared memory. */ if (localControlFile) { memcpy(ControlFile, localControlFile, sizeof(ControlFileData)); pfree(localControlFile); } /* * Since XLogCtlData contains XLogRecPtr fields, its sizeof should be a * multiple of the alignment for same, so no extra alignment padding is * needed here. */ allocptr = ((char *) XLogCtl) + sizeof(XLogCtlData); XLogCtl->xlblocks = (XLogRecPtr *) allocptr; memset(XLogCtl->xlblocks, 0, sizeof(XLogRecPtr) * XLOGbuffers); allocptr += sizeof(XLogRecPtr) * XLOGbuffers; /* WAL insertion locks. Ensure they're aligned to the full padded size */ allocptr += sizeof(WALInsertLockPadded) - ((uintptr_t) allocptr) % sizeof(WALInsertLockPadded); WALInsertLocks = XLogCtl->Insert.WALInsertLocks = (WALInsertLockPadded *) allocptr; allocptr += sizeof(WALInsertLockPadded) * NUM_XLOGINSERT_LOCKS; LWLockRegisterTranche(LWTRANCHE_WAL_INSERT, "wal_insert"); for (i = 0; i < NUM_XLOGINSERT_LOCKS; i++) { LWLockInitialize(&WALInsertLocks[i].l.lock, LWTRANCHE_WAL_INSERT); WALInsertLocks[i].l.insertingAt = InvalidXLogRecPtr; WALInsertLocks[i].l.lastImportantAt = InvalidXLogRecPtr; } /* * Align the start of the page buffers to a full xlog block size boundary. * This simplifies some calculations in XLOG insertion. It is also * required for O_DIRECT. */ allocptr = (char *) TYPEALIGN(XLOG_BLCKSZ, allocptr); XLogCtl->pages = allocptr; memset(XLogCtl->pages, 0, (Size) XLOG_BLCKSZ * XLOGbuffers); /* * Do basic initialization of XLogCtl shared data. (StartupXLOG will fill * in additional info.) */ XLogCtl->XLogCacheBlck = XLOGbuffers - 1; XLogCtl->SharedRecoveryInProgress = true; XLogCtl->SharedHotStandbyActive = false; XLogCtl->WalWriterSleeping = false; SpinLockInit(&XLogCtl->Insert.insertpos_lck); SpinLockInit(&XLogCtl->info_lck); SpinLockInit(&XLogCtl->ulsn_lck); InitSharedLatch(&XLogCtl->recoveryWakeupLatch); } /* * This func must be called ONCE on system install. It creates pg_control * and the initial XLOG segment. */ void BootStrapXLOG(void) { CheckPoint checkPoint; char *buffer; XLogPageHeader page; XLogLongPageHeader longpage; XLogRecord *record; char *recptr; bool use_existent; uint64 sysidentifier; char mock_auth_nonce[MOCK_AUTH_NONCE_LEN]; struct timeval tv; pg_crc32c crc; /* * Select a hopefully-unique system identifier code for this installation. * We use the result of gettimeofday(), including the fractional seconds * field, as being about as unique as we can easily get. (Think not to * use random(), since it hasn't been seeded and there's no portable way * to seed it other than the system clock value...) The upper half of the * uint64 value is just the tv_sec part, while the lower half contains the * tv_usec part (which must fit in 20 bits), plus 12 bits from our current * PID for a little extra uniqueness. A person knowing this encoding can * determine the initialization time of the installation, which could * perhaps be useful sometimes. */ gettimeofday(&tv, NULL); sysidentifier = ((uint64) tv.tv_sec) << 32; sysidentifier |= ((uint64) tv.tv_usec) << 12; sysidentifier |= getpid() & 0xFFF; /* * Generate a random nonce. This is used for authentication requests that * will fail because the user does not exist. The nonce is used to create * a genuine-looking password challenge for the non-existent user, in lieu * of an actual stored password. */ if (!pg_strong_random(mock_auth_nonce, MOCK_AUTH_NONCE_LEN)) ereport(PANIC, (errcode(ERRCODE_INTERNAL_ERROR), errmsg("could not generate secret authorization token"))); /* First timeline ID is always 1 */ ThisTimeLineID = 1; /* page buffer must be aligned suitably for O_DIRECT */ buffer = (char *) palloc(XLOG_BLCKSZ + XLOG_BLCKSZ); page = (XLogPageHeader) TYPEALIGN(XLOG_BLCKSZ, buffer); memset(page, 0, XLOG_BLCKSZ); /* * Set up information for the initial checkpoint record * * The initial checkpoint record is written to the beginning of the WAL * segment with logid=0 logseg=1. The very first WAL segment, 0/0, is not * used, so that we can use 0/0 to mean "before any valid WAL segment". */ checkPoint.redo = wal_segment_size + SizeOfXLogLongPHD; checkPoint.ThisTimeLineID = ThisTimeLineID; checkPoint.PrevTimeLineID = ThisTimeLineID; checkPoint.fullPageWrites = fullPageWrites; checkPoint.nextFullXid = FullTransactionIdFromEpochAndXid(0, FirstNormalTransactionId); checkPoint.nextOid = FirstBootstrapObjectId; checkPoint.nextMulti = FirstMultiXactId; checkPoint.nextMultiOffset = 0; checkPoint.oldestXid = FirstNormalTransactionId; checkPoint.oldestXidDB = TemplateDbOid; checkPoint.oldestMulti = FirstMultiXactId; checkPoint.oldestMultiDB = TemplateDbOid; checkPoint.oldestCommitTsXid = InvalidTransactionId; checkPoint.newestCommitTsXid = InvalidTransactionId; checkPoint.time = (pg_time_t) time(NULL); checkPoint.oldestActiveXid = InvalidTransactionId; ShmemVariableCache->nextFullXid = checkPoint.nextFullXid; ShmemVariableCache->nextOid = checkPoint.nextOid; ShmemVariableCache->oidCount = 0; MultiXactSetNextMXact(checkPoint.nextMulti, checkPoint.nextMultiOffset); AdvanceOldestClogXid(checkPoint.oldestXid); SetTransactionIdLimit(checkPoint.oldestXid, checkPoint.oldestXidDB); SetMultiXactIdLimit(checkPoint.oldestMulti, checkPoint.oldestMultiDB, true); SetCommitTsLimit(InvalidTransactionId, InvalidTransactionId); /* Set up the XLOG page header */ page->xlp_magic = XLOG_PAGE_MAGIC; page->xlp_info = XLP_LONG_HEADER; page->xlp_tli = ThisTimeLineID; page->xlp_pageaddr = wal_segment_size; longpage = (XLogLongPageHeader) page; longpage->xlp_sysid = sysidentifier; longpage->xlp_seg_size = wal_segment_size; longpage->xlp_xlog_blcksz = XLOG_BLCKSZ; /* Insert the initial checkpoint record */ recptr = ((char *) page + SizeOfXLogLongPHD); record = (XLogRecord *) recptr; record->xl_prev = 0; record->xl_xid = InvalidTransactionId; record->xl_tot_len = SizeOfXLogRecord + SizeOfXLogRecordDataHeaderShort + sizeof(checkPoint); record->xl_info = XLOG_CHECKPOINT_SHUTDOWN; record->xl_rmid = RM_XLOG_ID; recptr += SizeOfXLogRecord; /* fill the XLogRecordDataHeaderShort struct */ *(recptr++) = (char) XLR_BLOCK_ID_DATA_SHORT; *(recptr++) = sizeof(checkPoint); memcpy(recptr, &checkPoint, sizeof(checkPoint)); recptr += sizeof(checkPoint); Assert(recptr - (char *) record == record->xl_tot_len); INIT_CRC32C(crc); COMP_CRC32C(crc, ((char *) record) + SizeOfXLogRecord, record->xl_tot_len - SizeOfXLogRecord); COMP_CRC32C(crc, (char *) record, offsetof(XLogRecord, xl_crc)); FIN_CRC32C(crc); record->xl_crc = crc; /* Create first XLOG segment file */ use_existent = false; openLogFile = XLogFileInit(1, &use_existent, false); /* Write the first page with the initial record */ errno = 0; pgstat_report_wait_start(WAIT_EVENT_WAL_BOOTSTRAP_WRITE); if (write(openLogFile, page, XLOG_BLCKSZ) != XLOG_BLCKSZ) { /* if write didn't set errno, assume problem is no disk space */ if (errno == 0) errno = ENOSPC; ereport(PANIC, (errcode_for_file_access(), errmsg("could not write bootstrap write-ahead log file: %m"))); } pgstat_report_wait_end(); pgstat_report_wait_start(WAIT_EVENT_WAL_BOOTSTRAP_SYNC); if (pg_fsync(openLogFile) != 0) ereport(PANIC, (errcode_for_file_access(), errmsg("could not fsync bootstrap write-ahead log file: %m"))); pgstat_report_wait_end(); if (close(openLogFile) != 0) ereport(PANIC, (errcode_for_file_access(), errmsg("could not close bootstrap write-ahead log file: %m"))); openLogFile = -1; /* Now create pg_control */ memset(ControlFile, 0, sizeof(ControlFileData)); /* Initialize pg_control status fields */ ControlFile->system_identifier = sysidentifier; memcpy(ControlFile->mock_authentication_nonce, mock_auth_nonce, MOCK_AUTH_NONCE_LEN); ControlFile->state = DB_SHUTDOWNED; ControlFile->time = checkPoint.time; ControlFile->checkPoint = checkPoint.redo; ControlFile->checkPointCopy = checkPoint; ControlFile->unloggedLSN = FirstNormalUnloggedLSN; /* Set important parameter values for use when replaying WAL */ ControlFile->MaxConnections = MaxConnections; ControlFile->max_worker_processes = max_worker_processes; ControlFile->max_wal_senders = max_wal_senders; ControlFile->max_prepared_xacts = max_prepared_xacts; ControlFile->max_locks_per_xact = max_locks_per_xact; ControlFile->wal_level = wal_level; ControlFile->wal_log_hints = wal_log_hints; ControlFile->track_commit_timestamp = track_commit_timestamp; ControlFile->data_checksum_version = bootstrap_data_checksum_version; /* some additional ControlFile fields are set in WriteControlFile() */ WriteControlFile(); /* Bootstrap the commit log, too */ BootStrapCLOG(); BootStrapCommitTs(); BootStrapSUBTRANS(); BootStrapMultiXact(); pfree(buffer); /* * Force control file to be read - in contrast to normal processing we'd * otherwise never run the checks and GUC related initializations therein. */ ReadControlFile(); } static char * str_time(pg_time_t tnow) { static char buf[128]; pg_strftime(buf, sizeof(buf), "%Y-%m-%d %H:%M:%S %Z", pg_localtime(&tnow, log_timezone)); return buf; } /* * See if there are any recovery signal files and if so, set state for * recovery. * * See if there is a recovery command file (recovery.conf), and if so * throw an ERROR since as of PG12 we no longer recognize that. */ static void readRecoverySignalFile(void) { struct stat stat_buf; if (IsBootstrapProcessingMode()) return; /* * Check for old recovery API file: recovery.conf */ if (stat(RECOVERY_COMMAND_FILE, &stat_buf) == 0) ereport(FATAL, (errcode_for_file_access(), errmsg("using recovery command file \"%s\" is not supported", RECOVERY_COMMAND_FILE))); /* * Remove unused .done file, if present. Ignore if absent. */ unlink(RECOVERY_COMMAND_DONE); /* * Check for recovery signal files and if found, fsync them since they * represent server state information. We don't sweat too much about the * possibility of fsync failure, however. * * If present, standby signal file takes precedence. If neither is present * then we won't enter archive recovery. */ if (stat(STANDBY_SIGNAL_FILE, &stat_buf) == 0) { int fd; fd = BasicOpenFilePerm(STANDBY_SIGNAL_FILE, O_RDWR | PG_BINARY | get_sync_bit(sync_method), S_IRUSR | S_IWUSR); if (fd >= 0) { (void) pg_fsync(fd); close(fd); } standby_signal_file_found = true; } else if (stat(RECOVERY_SIGNAL_FILE, &stat_buf) == 0) { int fd; fd = BasicOpenFilePerm(RECOVERY_SIGNAL_FILE, O_RDWR | PG_BINARY | get_sync_bit(sync_method), S_IRUSR | S_IWUSR); if (fd >= 0) { (void) pg_fsync(fd); close(fd); } recovery_signal_file_found = true; } StandbyModeRequested = false; ArchiveRecoveryRequested = false; if (standby_signal_file_found) { StandbyModeRequested = true; ArchiveRecoveryRequested = true; } else if (recovery_signal_file_found) { StandbyModeRequested = false; ArchiveRecoveryRequested = true; } else return; /* * We don't support standby mode in standalone backends; that requires * other processes such as the WAL receiver to be alive. */ if (StandbyModeRequested && !IsUnderPostmaster) ereport(FATAL, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("standby mode is not supported by single-user servers"))); } static void validateRecoveryParameters(void) { if (!ArchiveRecoveryRequested) return; /* * Check for compulsory parameters */ if (StandbyModeRequested) { if ((PrimaryConnInfo == NULL || strcmp(PrimaryConnInfo, "") == 0) && (recoveryRestoreCommand == NULL || strcmp(recoveryRestoreCommand, "") == 0)) ereport(WARNING, (errmsg("specified neither primary_conninfo nor restore_command"), errhint("The database server will regularly poll the pg_wal subdirectory to check for files placed there."))); } else { if (recoveryRestoreCommand == NULL || strcmp(recoveryRestoreCommand, "") == 0) ereport(FATAL, (errcode(ERRCODE_INVALID_PARAMETER_VALUE), errmsg("must specify restore_command when standby mode is not enabled"))); } /* * Override any inconsistent requests. Note that this is a change of * behaviour in 9.5; prior to this we simply ignored a request to pause if * hot_standby = off, which was surprising behaviour. */ if (recoveryTargetAction == RECOVERY_TARGET_ACTION_PAUSE && !EnableHotStandby) recoveryTargetAction = RECOVERY_TARGET_ACTION_SHUTDOWN; /* * Final parsing of recovery_target_time string; see also * check_recovery_target_time(). */ if (recoveryTarget == RECOVERY_TARGET_TIME) { recoveryTargetTime = DatumGetTimestampTz(DirectFunctionCall3(timestamptz_in, CStringGetDatum(recovery_target_time_string), ObjectIdGetDatum(InvalidOid), Int32GetDatum(-1))); } /* * If user specified recovery_target_timeline, validate it or compute the * "latest" value. We can't do this until after we've gotten the restore * command and set InArchiveRecovery, because we need to fetch timeline * history files from the archive. */ if (recoveryTargetTimeLineGoal == RECOVERY_TARGET_TIMELINE_NUMERIC) { TimeLineID rtli = recoveryTargetTLIRequested; /* Timeline 1 does not have a history file, all else should */ if (rtli != 1 && !existsTimeLineHistory(rtli)) ereport(FATAL, (errcode(ERRCODE_INVALID_PARAMETER_VALUE), errmsg("recovery target timeline %u does not exist", rtli))); recoveryTargetTLI = rtli; } else if (recoveryTargetTimeLineGoal == RECOVERY_TARGET_TIMELINE_LATEST) { /* We start the "latest" search from pg_control's timeline */ recoveryTargetTLI = findNewestTimeLine(recoveryTargetTLI); } else { /* * else we just use the recoveryTargetTLI as already read from * ControlFile */ Assert(recoveryTargetTimeLineGoal == RECOVERY_TARGET_TIMELINE_CONTROLFILE); } } /* * Exit archive-recovery state */ static void exitArchiveRecovery(TimeLineID endTLI, XLogRecPtr endOfLog) { char xlogfname[MAXFNAMELEN]; XLogSegNo endLogSegNo; XLogSegNo startLogSegNo; /* we always switch to a new timeline after archive recovery */ Assert(endTLI != ThisTimeLineID); /* * We are no longer in archive recovery state. */ InArchiveRecovery = false; /* * Update min recovery point one last time. */ UpdateMinRecoveryPoint(InvalidXLogRecPtr, true); /* * If the ending log segment is still open, close it (to avoid problems on * Windows with trying to rename or delete an open file). */ if (readFile >= 0) { close(readFile); readFile = -1; } /* * Calculate the last segment on the old timeline, and the first segment * on the new timeline. If the switch happens in the middle of a segment, * they are the same, but if the switch happens exactly at a segment * boundary, startLogSegNo will be endLogSegNo + 1. */ XLByteToPrevSeg(endOfLog, endLogSegNo, wal_segment_size); XLByteToSeg(endOfLog, startLogSegNo, wal_segment_size); /* * Initialize the starting WAL segment for the new timeline. If the switch * happens in the middle of a segment, copy data from the last WAL segment * of the old timeline up to the switch point, to the starting WAL segment * on the new timeline. */ if (endLogSegNo == startLogSegNo) { /* * Make a copy of the file on the new timeline. * * Writing WAL isn't allowed yet, so there are no locking * considerations. But we should be just as tense as XLogFileInit to * avoid emplacing a bogus file. */ XLogFileCopy(endLogSegNo, endTLI, endLogSegNo, XLogSegmentOffset(endOfLog, wal_segment_size)); } else { /* * The switch happened at a segment boundary, so just create the next * segment on the new timeline. */ bool use_existent = true; int fd; fd = XLogFileInit(startLogSegNo, &use_existent, true); if (close(fd) != 0) { char xlogfname[MAXFNAMELEN]; int save_errno = errno; XLogFileName(xlogfname, ThisTimeLineID, startLogSegNo, wal_segment_size); errno = save_errno; ereport(ERROR, (errcode_for_file_access(), errmsg("could not close file \"%s\": %m", xlogfname))); } } /* * Let's just make real sure there are not .ready or .done flags posted * for the new segment. */ XLogFileName(xlogfname, ThisTimeLineID, startLogSegNo, wal_segment_size); XLogArchiveCleanup(xlogfname); /* * Remove the signal files out of the way, so that we don't accidentally * re-enter archive recovery mode in a subsequent crash. */ if (standby_signal_file_found) durable_unlink(STANDBY_SIGNAL_FILE, FATAL); if (recovery_signal_file_found) durable_unlink(RECOVERY_SIGNAL_FILE, FATAL); ereport(LOG, (errmsg("archive recovery complete"))); } /* * Extract timestamp from WAL record. * * If the record contains a timestamp, returns true, and saves the timestamp * in *recordXtime. If the record type has no timestamp, returns false. * Currently, only transaction commit/abort records and restore points contain * timestamps. */ static bool getRecordTimestamp(XLogReaderState *record, TimestampTz *recordXtime) { uint8 info = XLogRecGetInfo(record) & ~XLR_INFO_MASK; uint8 xact_info = info & XLOG_XACT_OPMASK; uint8 rmid = XLogRecGetRmid(record); if (rmid == RM_XLOG_ID && info == XLOG_RESTORE_POINT) { *recordXtime = ((xl_restore_point *) XLogRecGetData(record))->rp_time; return true; } if (rmid == RM_XACT_ID && (xact_info == XLOG_XACT_COMMIT || xact_info == XLOG_XACT_COMMIT_PREPARED)) { *recordXtime = ((xl_xact_commit *) XLogRecGetData(record))->xact_time; return true; } if (rmid == RM_XACT_ID && (xact_info == XLOG_XACT_ABORT || xact_info == XLOG_XACT_ABORT_PREPARED)) { *recordXtime = ((xl_xact_abort *) XLogRecGetData(record))->xact_time; return true; } return false; } /* * For point-in-time recovery, this function decides whether we want to * stop applying the XLOG before the current record. * * Returns true if we are stopping, false otherwise. If stopping, some * information is saved in recoveryStopXid et al for use in annotating the * new timeline's history file. */ static bool recoveryStopsBefore(XLogReaderState *record) { bool stopsHere = false; uint8 xact_info; bool isCommit; TimestampTz recordXtime = 0; TransactionId recordXid; /* * Ignore recovery target settings when not in archive recovery (meaning * we are in crash recovery). */ if (!ArchiveRecoveryRequested) return false; /* Check if we should stop as soon as reaching consistency */ if (recoveryTarget == RECOVERY_TARGET_IMMEDIATE && reachedConsistency) { ereport(LOG, (errmsg("recovery stopping after reaching consistency"))); recoveryStopAfter = false; recoveryStopXid = InvalidTransactionId; recoveryStopLSN = InvalidXLogRecPtr; recoveryStopTime = 0; recoveryStopName[0] = '\0'; return true; } /* Check if target LSN has been reached */ if (recoveryTarget == RECOVERY_TARGET_LSN && !recoveryTargetInclusive && record->ReadRecPtr >= recoveryTargetLSN) { recoveryStopAfter = false; recoveryStopXid = InvalidTransactionId; recoveryStopLSN = record->ReadRecPtr; recoveryStopTime = 0; recoveryStopName[0] = '\0'; ereport(LOG, (errmsg("recovery stopping before WAL location (LSN) \"%X/%X\"", (uint32) (recoveryStopLSN >> 32), (uint32) recoveryStopLSN))); return true; } /* Otherwise we only consider stopping before COMMIT or ABORT records. */ if (XLogRecGetRmid(record) != RM_XACT_ID) return false; xact_info = XLogRecGetInfo(record) & XLOG_XACT_OPMASK; if (xact_info == XLOG_XACT_COMMIT) { isCommit = true; recordXid = XLogRecGetXid(record); } else if (xact_info == XLOG_XACT_COMMIT_PREPARED) { xl_xact_commit *xlrec = (xl_xact_commit *) XLogRecGetData(record); xl_xact_parsed_commit parsed; isCommit = true; ParseCommitRecord(XLogRecGetInfo(record), xlrec, &parsed); recordXid = parsed.twophase_xid; } else if (xact_info == XLOG_XACT_ABORT) { isCommit = false; recordXid = XLogRecGetXid(record); } else if (xact_info == XLOG_XACT_ABORT_PREPARED) { xl_xact_abort *xlrec = (xl_xact_abort *) XLogRecGetData(record); xl_xact_parsed_abort parsed; isCommit = true; ParseAbortRecord(XLogRecGetInfo(record), xlrec, &parsed); recordXid = parsed.twophase_xid; } else return false; if (recoveryTarget == RECOVERY_TARGET_XID && !recoveryTargetInclusive) { /* * There can be only one transaction end record with this exact * transactionid * * when testing for an xid, we MUST test for equality only, since * transactions are numbered in the order they start, not the order * they complete. A higher numbered xid will complete before you about * 50% of the time... */ stopsHere = (recordXid == recoveryTargetXid); } if (recoveryTarget == RECOVERY_TARGET_TIME && getRecordTimestamp(record, &recordXtime)) { /* * There can be many transactions that share the same commit time, so * we stop after the last one, if we are inclusive, or stop at the * first one if we are exclusive */ if (recoveryTargetInclusive) stopsHere = (recordXtime > recoveryTargetTime); else stopsHere = (recordXtime >= recoveryTargetTime); } if (stopsHere) { recoveryStopAfter = false; recoveryStopXid = recordXid; recoveryStopTime = recordXtime; recoveryStopLSN = InvalidXLogRecPtr; recoveryStopName[0] = '\0'; if (isCommit) { ereport(LOG, (errmsg("recovery stopping before commit of transaction %u, time %s", recoveryStopXid, timestamptz_to_str(recoveryStopTime)))); } else { ereport(LOG, (errmsg("recovery stopping before abort of transaction %u, time %s", recoveryStopXid, timestamptz_to_str(recoveryStopTime)))); } } return stopsHere; } /* * Same as recoveryStopsBefore, but called after applying the record. * * We also track the timestamp of the latest applied COMMIT/ABORT * record in XLogCtl->recoveryLastXTime. */ static bool recoveryStopsAfter(XLogReaderState *record) { uint8 info; uint8 xact_info; uint8 rmid; TimestampTz recordXtime; /* * Ignore recovery target settings when not in archive recovery (meaning * we are in crash recovery). */ if (!ArchiveRecoveryRequested) return false; info = XLogRecGetInfo(record) & ~XLR_INFO_MASK; rmid = XLogRecGetRmid(record); /* * There can be many restore points that share the same name; we stop at * the first one. */ if (recoveryTarget == RECOVERY_TARGET_NAME && rmid == RM_XLOG_ID && info == XLOG_RESTORE_POINT) { xl_restore_point *recordRestorePointData; recordRestorePointData = (xl_restore_point *) XLogRecGetData(record); if (strcmp(recordRestorePointData->rp_name, recoveryTargetName) == 0) { recoveryStopAfter = true; recoveryStopXid = InvalidTransactionId; recoveryStopLSN = InvalidXLogRecPtr; (void) getRecordTimestamp(record, &recoveryStopTime); strlcpy(recoveryStopName, recordRestorePointData->rp_name, MAXFNAMELEN); ereport(LOG, (errmsg("recovery stopping at restore point \"%s\", time %s", recoveryStopName, timestamptz_to_str(recoveryStopTime)))); return true; } } /* Check if the target LSN has been reached */ if (recoveryTarget == RECOVERY_TARGET_LSN && recoveryTargetInclusive && record->ReadRecPtr >= recoveryTargetLSN) { recoveryStopAfter = true; recoveryStopXid = InvalidTransactionId; recoveryStopLSN = record->ReadRecPtr; recoveryStopTime = 0; recoveryStopName[0] = '\0'; ereport(LOG, (errmsg("recovery stopping after WAL location (LSN) \"%X/%X\"", (uint32) (recoveryStopLSN >> 32), (uint32) recoveryStopLSN))); return true; } if (rmid != RM_XACT_ID) return false; xact_info = info & XLOG_XACT_OPMASK; if (xact_info == XLOG_XACT_COMMIT || xact_info == XLOG_XACT_COMMIT_PREPARED || xact_info == XLOG_XACT_ABORT || xact_info == XLOG_XACT_ABORT_PREPARED) { TransactionId recordXid; /* Update the last applied transaction timestamp */ if (getRecordTimestamp(record, &recordXtime)) SetLatestXTime(recordXtime); /* Extract the XID of the committed/aborted transaction */ if (xact_info == XLOG_XACT_COMMIT_PREPARED) { xl_xact_commit *xlrec = (xl_xact_commit *) XLogRecGetData(record); xl_xact_parsed_commit parsed; ParseCommitRecord(XLogRecGetInfo(record), xlrec, &parsed); recordXid = parsed.twophase_xid; } else if (xact_info == XLOG_XACT_ABORT_PREPARED) { xl_xact_abort *xlrec = (xl_xact_abort *) XLogRecGetData(record); xl_xact_parsed_abort parsed; ParseAbortRecord(XLogRecGetInfo(record), xlrec, &parsed); recordXid = parsed.twophase_xid; } else recordXid = XLogRecGetXid(record); /* * There can be only one transaction end record with this exact * transactionid * * when testing for an xid, we MUST test for equality only, since * transactions are numbered in the order they start, not the order * they complete. A higher numbered xid will complete before you about * 50% of the time... */ if (recoveryTarget == RECOVERY_TARGET_XID && recoveryTargetInclusive && recordXid == recoveryTargetXid) { recoveryStopAfter = true; recoveryStopXid = recordXid; recoveryStopTime = recordXtime; recoveryStopLSN = InvalidXLogRecPtr; recoveryStopName[0] = '\0'; if (xact_info == XLOG_XACT_COMMIT || xact_info == XLOG_XACT_COMMIT_PREPARED) { ereport(LOG, (errmsg("recovery stopping after commit of transaction %u, time %s", recoveryStopXid, timestamptz_to_str(recoveryStopTime)))); } else if (xact_info == XLOG_XACT_ABORT || xact_info == XLOG_XACT_ABORT_PREPARED) { ereport(LOG, (errmsg("recovery stopping after abort of transaction %u, time %s", recoveryStopXid, timestamptz_to_str(recoveryStopTime)))); } return true; } } /* Check if we should stop as soon as reaching consistency */ if (recoveryTarget == RECOVERY_TARGET_IMMEDIATE && reachedConsistency) { ereport(LOG, (errmsg("recovery stopping after reaching consistency"))); recoveryStopAfter = true; recoveryStopXid = InvalidTransactionId; recoveryStopTime = 0; recoveryStopLSN = InvalidXLogRecPtr; recoveryStopName[0] = '\0'; return true; } return false; } /* * Wait until shared recoveryPause flag is cleared. * * XXX Could also be done with shared latch, avoiding the pg_usleep loop. * Probably not worth the trouble though. This state shouldn't be one that * anyone cares about server power consumption in. */ static void recoveryPausesHere(void) { /* Don't pause unless users can connect! */ if (!LocalHotStandbyActive) return; ereport(LOG, (errmsg("recovery has paused"), errhint("Execute pg_wal_replay_resume() to continue."))); while (RecoveryIsPaused()) { pg_usleep(1000000L); /* 1000 ms */ HandleStartupProcInterrupts(); } } bool RecoveryIsPaused(void) { bool recoveryPause; SpinLockAcquire(&XLogCtl->info_lck); recoveryPause = XLogCtl->recoveryPause; SpinLockRelease(&XLogCtl->info_lck); return recoveryPause; } void SetRecoveryPause(bool recoveryPause) { SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->recoveryPause = recoveryPause; SpinLockRelease(&XLogCtl->info_lck); } /* * When recovery_min_apply_delay is set, we wait long enough to make sure * certain record types are applied at least that interval behind the master. * * Returns true if we waited. * * Note that the delay is calculated between the WAL record log time and * the current time on standby. We would prefer to keep track of when this * standby received each WAL record, which would allow a more consistent * approach and one not affected by time synchronisation issues, but that * is significantly more effort and complexity for little actual gain in * usability. */ static bool recoveryApplyDelay(XLogReaderState *record) { uint8 xact_info; TimestampTz xtime; TimestampTz delayUntil; long secs; int microsecs; /* nothing to do if no delay configured */ if (recovery_min_apply_delay <= 0) return false; /* no delay is applied on a database not yet consistent */ if (!reachedConsistency) return false; /* nothing to do if crash recovery is requested */ if (!ArchiveRecoveryRequested) return false; /* * Is it a COMMIT record? * * We deliberately choose not to delay aborts since they have no effect on * MVCC. We already allow replay of records that don't have a timestamp, * so there is already opportunity for issues caused by early conflicts on * standbys. */ if (XLogRecGetRmid(record) != RM_XACT_ID) return false; xact_info = XLogRecGetInfo(record) & XLOG_XACT_OPMASK; if (xact_info != XLOG_XACT_COMMIT && xact_info != XLOG_XACT_COMMIT_PREPARED) return false; if (!getRecordTimestamp(record, &xtime)) return false; delayUntil = TimestampTzPlusMilliseconds(xtime, recovery_min_apply_delay); /* * Exit without arming the latch if it's already past time to apply this * record */ TimestampDifference(GetCurrentTimestamp(), delayUntil, &secs, µsecs); if (secs <= 0 && microsecs <= 0) return false; while (true) { ResetLatch(&XLogCtl->recoveryWakeupLatch); /* might change the trigger file's location */ HandleStartupProcInterrupts(); if (CheckForStandbyTrigger()) break; /* * Wait for difference between GetCurrentTimestamp() and delayUntil */ TimestampDifference(GetCurrentTimestamp(), delayUntil, &secs, µsecs); /* * NB: We're ignoring waits below recovery_min_apply_delay's * resolution. */ if (secs <= 0 && microsecs / 1000 <= 0) break; elog(DEBUG2, "recovery apply delay %ld seconds, %d milliseconds", secs, microsecs / 1000); (void) WaitLatch(&XLogCtl->recoveryWakeupLatch, WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH, secs * 1000L + microsecs / 1000, WAIT_EVENT_RECOVERY_APPLY_DELAY); } return true; } /* * Save timestamp of latest processed commit/abort record. * * We keep this in XLogCtl, not a simple static variable, so that it can be * seen by processes other than the startup process. Note in particular * that CreateRestartPoint is executed in the checkpointer. */ static void SetLatestXTime(TimestampTz xtime) { SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->recoveryLastXTime = xtime; SpinLockRelease(&XLogCtl->info_lck); } /* * Fetch timestamp of latest processed commit/abort record. */ TimestampTz GetLatestXTime(void) { TimestampTz xtime; SpinLockAcquire(&XLogCtl->info_lck); xtime = XLogCtl->recoveryLastXTime; SpinLockRelease(&XLogCtl->info_lck); return xtime; } /* * Save timestamp of the next chunk of WAL records to apply. * * We keep this in XLogCtl, not a simple static variable, so that it can be * seen by all backends. */ static void SetCurrentChunkStartTime(TimestampTz xtime) { SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->currentChunkStartTime = xtime; SpinLockRelease(&XLogCtl->info_lck); } /* * Fetch timestamp of latest processed commit/abort record. * Startup process maintains an accurate local copy in XLogReceiptTime */ TimestampTz GetCurrentChunkReplayStartTime(void) { TimestampTz xtime; SpinLockAcquire(&XLogCtl->info_lck); xtime = XLogCtl->currentChunkStartTime; SpinLockRelease(&XLogCtl->info_lck); return xtime; } /* * Returns time of receipt of current chunk of XLOG data, as well as * whether it was received from streaming replication or from archives. */ void GetXLogReceiptTime(TimestampTz *rtime, bool *fromStream) { /* * This must be executed in the startup process, since we don't export the * relevant state to shared memory. */ Assert(InRecovery); *rtime = XLogReceiptTime; *fromStream = (XLogReceiptSource == XLOG_FROM_STREAM); } /* * Note that text field supplied is a parameter name and does not require * translation */ #define RecoveryRequiresIntParameter(param_name, currValue, minValue) \ do { \ if ((currValue) < (minValue)) \ ereport(ERROR, \ (errcode(ERRCODE_INVALID_PARAMETER_VALUE), \ errmsg("hot standby is not possible because %s = %d is a lower setting than on the master server (its value was %d)", \ param_name, \ currValue, \ minValue))); \ } while(0) /* * Check to see if required parameters are set high enough on this server * for various aspects of recovery operation. * * Note that all the parameters which this function tests need to be * listed in Administrator's Overview section in high-availability.sgml. * If you change them, don't forget to update the list. */ static void CheckRequiredParameterValues(void) { /* * For archive recovery, the WAL must be generated with at least 'replica' * wal_level. */ if (ArchiveRecoveryRequested && ControlFile->wal_level == WAL_LEVEL_MINIMAL) { ereport(WARNING, (errmsg("WAL was generated with wal_level=minimal, data may be missing"), errhint("This happens if you temporarily set wal_level=minimal without taking a new base backup."))); } /* * For Hot Standby, the WAL must be generated with 'replica' mode, and we * must have at least as many backend slots as the primary. */ if (ArchiveRecoveryRequested && EnableHotStandby) { if (ControlFile->wal_level < WAL_LEVEL_REPLICA) ereport(ERROR, (errmsg("hot standby is not possible because wal_level was not set to \"replica\" or higher on the master server"), errhint("Either set wal_level to \"replica\" on the master, or turn off hot_standby here."))); /* We ignore autovacuum_max_workers when we make this test. */ RecoveryRequiresIntParameter("max_connections", MaxConnections, ControlFile->MaxConnections); RecoveryRequiresIntParameter("max_worker_processes", max_worker_processes, ControlFile->max_worker_processes); RecoveryRequiresIntParameter("max_wal_senders", max_wal_senders, ControlFile->max_wal_senders); RecoveryRequiresIntParameter("max_prepared_transactions", max_prepared_xacts, ControlFile->max_prepared_xacts); RecoveryRequiresIntParameter("max_locks_per_transaction", max_locks_per_xact, ControlFile->max_locks_per_xact); } } /* * This must be called ONCE during postmaster or standalone-backend startup */ void StartupXLOG(void) { XLogCtlInsert *Insert; CheckPoint checkPoint; bool wasShutdown; bool reachedStopPoint = false; bool haveBackupLabel = false; bool haveTblspcMap = false; XLogRecPtr RecPtr, checkPointLoc, EndOfLog; TimeLineID EndOfLogTLI; TimeLineID PrevTimeLineID; XLogRecord *record; TransactionId oldestActiveXID; bool backupEndRequired = false; bool backupFromStandby = false; DBState dbstate_at_startup; XLogReaderState *xlogreader; XLogPageReadPrivate private; bool fast_promoted = false; struct stat st; /* * We should have an aux process resource owner to use, and we should not * be in a transaction that's installed some other resowner. */ Assert(AuxProcessResourceOwner != NULL); Assert(CurrentResourceOwner == NULL || CurrentResourceOwner == AuxProcessResourceOwner); CurrentResourceOwner = AuxProcessResourceOwner; /* * Check that contents look valid. */ if (!XRecOffIsValid(ControlFile->checkPoint)) ereport(FATAL, (errmsg("control file contains invalid checkpoint location"))); switch (ControlFile->state) { case DB_SHUTDOWNED: /* This is the expected case, so don't be chatty in standalone mode */ ereport(IsPostmasterEnvironment ? LOG : NOTICE, (errmsg("database system was shut down at %s", str_time(ControlFile->time)))); break; case DB_SHUTDOWNED_IN_RECOVERY: ereport(LOG, (errmsg("database system was shut down in recovery at %s", str_time(ControlFile->time)))); break; case DB_SHUTDOWNING: ereport(LOG, (errmsg("database system shutdown was interrupted; last known up at %s", str_time(ControlFile->time)))); break; case DB_IN_CRASH_RECOVERY: ereport(LOG, (errmsg("database system was interrupted while in recovery at %s", str_time(ControlFile->time)), errhint("This probably means that some data is corrupted and" " you will have to use the last backup for recovery."))); break; case DB_IN_ARCHIVE_RECOVERY: ereport(LOG, (errmsg("database system was interrupted while in recovery at log time %s", str_time(ControlFile->checkPointCopy.time)), errhint("If this has occurred more than once some data might be corrupted" " and you might need to choose an earlier recovery target."))); break; case DB_IN_PRODUCTION: ereport(LOG, (errmsg("database system was interrupted; last known up at %s", str_time(ControlFile->time)))); break; default: ereport(FATAL, (errmsg("control file contains invalid database cluster state"))); } /* This is just to allow attaching to startup process with a debugger */ #ifdef XLOG_REPLAY_DELAY if (ControlFile->state != DB_SHUTDOWNED) pg_usleep(60000000L); #endif /* * Verify that pg_wal and pg_wal/archive_status exist. In cases where * someone has performed a copy for PITR, these directories may have been * excluded and need to be re-created. */ ValidateXLOGDirectoryStructure(); /*---------- * If we previously crashed, perform a couple of actions: * - The pg_wal directory may still include some temporary WAL segments * used when creating a new segment, so perform some clean up to not * bloat this path. This is done first as there is no point to sync this * temporary data. * - There might be data which we had written, intending to fsync it, * but which we had not actually fsync'd yet. Therefore, a power failure * in the near future might cause earlier unflushed writes to be lost, * even though more recent data written to disk from here on would be * persisted. To avoid that, fsync the entire data directory. *--------- */ if (ControlFile->state != DB_SHUTDOWNED && ControlFile->state != DB_SHUTDOWNED_IN_RECOVERY) { RemoveTempXlogFiles(); SyncDataDirectory(); } /* * Initialize on the assumption we want to recover to the latest timeline * that's active according to pg_control. */ if (ControlFile->minRecoveryPointTLI > ControlFile->checkPointCopy.ThisTimeLineID) recoveryTargetTLI = ControlFile->minRecoveryPointTLI; else recoveryTargetTLI = ControlFile->checkPointCopy.ThisTimeLineID; /* * Check for signal files, and if so set up state for offline recovery */ readRecoverySignalFile(); validateRecoveryParameters(); if (ArchiveRecoveryRequested) { if (StandbyModeRequested) ereport(LOG, (errmsg("entering standby mode"))); else if (recoveryTarget == RECOVERY_TARGET_XID) ereport(LOG, (errmsg("starting point-in-time recovery to XID %u", recoveryTargetXid))); else if (recoveryTarget == RECOVERY_TARGET_TIME) ereport(LOG, (errmsg("starting point-in-time recovery to %s", timestamptz_to_str(recoveryTargetTime)))); else if (recoveryTarget == RECOVERY_TARGET_NAME) ereport(LOG, (errmsg("starting point-in-time recovery to \"%s\"", recoveryTargetName))); else if (recoveryTarget == RECOVERY_TARGET_LSN) ereport(LOG, (errmsg("starting point-in-time recovery to WAL location (LSN) \"%X/%X\"", (uint32) (recoveryTargetLSN >> 32), (uint32) recoveryTargetLSN))); else if (recoveryTarget == RECOVERY_TARGET_IMMEDIATE) ereport(LOG, (errmsg("starting point-in-time recovery to earliest consistent point"))); else ereport(LOG, (errmsg("starting archive recovery"))); } /* * Take ownership of the wakeup latch if we're going to sleep during * recovery. */ if (ArchiveRecoveryRequested) OwnLatch(&XLogCtl->recoveryWakeupLatch); /* Set up XLOG reader facility */ MemSet(&private, 0, sizeof(XLogPageReadPrivate)); xlogreader = XLogReaderAllocate(wal_segment_size, NULL, &XLogPageRead, &private); if (!xlogreader) ereport(ERROR, (errcode(ERRCODE_OUT_OF_MEMORY), errmsg("out of memory"), errdetail("Failed while allocating a WAL reading processor."))); xlogreader->system_identifier = ControlFile->system_identifier; /* * Allocate two page buffers dedicated to WAL consistency checks. We do * it this way, rather than just making static arrays, for two reasons: * (1) no need to waste the storage in most instantiations of the backend; * (2) a static char array isn't guaranteed to have any particular * alignment, whereas palloc() will provide MAXALIGN'd storage. */ replay_image_masked = (char *) palloc(BLCKSZ); master_image_masked = (char *) palloc(BLCKSZ); if (read_backup_label(&checkPointLoc, &backupEndRequired, &backupFromStandby)) { List *tablespaces = NIL; /* * Archive recovery was requested, and thanks to the backup label * file, we know how far we need to replay to reach consistency. Enter * archive recovery directly. */ InArchiveRecovery = true; if (StandbyModeRequested) StandbyMode = true; /* * When a backup_label file is present, we want to roll forward from * the checkpoint it identifies, rather than using pg_control. */ record = ReadCheckpointRecord(xlogreader, checkPointLoc, 0, true); if (record != NULL) { memcpy(&checkPoint, XLogRecGetData(xlogreader), sizeof(CheckPoint)); wasShutdown = ((record->xl_info & ~XLR_INFO_MASK) == XLOG_CHECKPOINT_SHUTDOWN); ereport(DEBUG1, (errmsg("checkpoint record is at %X/%X", (uint32) (checkPointLoc >> 32), (uint32) checkPointLoc))); InRecovery = true; /* force recovery even if SHUTDOWNED */ /* * Make sure that REDO location exists. This may not be the case * if there was a crash during an online backup, which left a * backup_label around that references a WAL segment that's * already been archived. */ if (checkPoint.redo < checkPointLoc) { XLogBeginRead(xlogreader, checkPoint.redo); if (!ReadRecord(xlogreader, LOG, false)) ereport(FATAL, (errmsg("could not find redo location referenced by checkpoint record"), errhint("If you are restoring from a backup, touch \"%s/recovery.signal\" and add required recovery options.\n" "If you are not restoring from a backup, try removing the file \"%s/backup_label\".\n" "Be careful: removing \"%s/backup_label\" will result in a corrupt cluster if restoring from a backup.", DataDir, DataDir, DataDir))); } } else { ereport(FATAL, (errmsg("could not locate required checkpoint record"), errhint("If you are restoring from a backup, touch \"%s/recovery.signal\" and add required recovery options.\n" "If you are not restoring from a backup, try removing the file \"%s/backup_label\".\n" "Be careful: removing \"%s/backup_label\" will result in a corrupt cluster if restoring from a backup.", DataDir, DataDir, DataDir))); wasShutdown = false; /* keep compiler quiet */ } /* read the tablespace_map file if present and create symlinks. */ if (read_tablespace_map(&tablespaces)) { ListCell *lc; foreach(lc, tablespaces) { tablespaceinfo *ti = lfirst(lc); char *linkloc; linkloc = psprintf("pg_tblspc/%s", ti->oid); /* * Remove the existing symlink if any and Create the symlink * under PGDATA. */ remove_tablespace_symlink(linkloc); if (symlink(ti->path, linkloc) < 0) ereport(ERROR, (errcode_for_file_access(), errmsg("could not create symbolic link \"%s\": %m", linkloc))); pfree(ti->oid); pfree(ti->path); pfree(ti); } /* set flag to delete it later */ haveTblspcMap = true; } /* set flag to delete it later */ haveBackupLabel = true; } else { /* * If tablespace_map file is present without backup_label file, there * is no use of such file. There is no harm in retaining it, but it * is better to get rid of the map file so that we don't have any * redundant file in data directory and it will avoid any sort of * confusion. It seems prudent though to just rename the file out of * the way rather than delete it completely, also we ignore any error * that occurs in rename operation as even if map file is present * without backup_label file, it is harmless. */ if (stat(TABLESPACE_MAP, &st) == 0) { unlink(TABLESPACE_MAP_OLD); if (durable_rename(TABLESPACE_MAP, TABLESPACE_MAP_OLD, DEBUG1) == 0) ereport(LOG, (errmsg("ignoring file \"%s\" because no file \"%s\" exists", TABLESPACE_MAP, BACKUP_LABEL_FILE), errdetail("File \"%s\" was renamed to \"%s\".", TABLESPACE_MAP, TABLESPACE_MAP_OLD))); else ereport(LOG, (errmsg("ignoring file \"%s\" because no file \"%s\" exists", TABLESPACE_MAP, BACKUP_LABEL_FILE), errdetail("Could not rename file \"%s\" to \"%s\": %m.", TABLESPACE_MAP, TABLESPACE_MAP_OLD))); } /* * It's possible that archive recovery was requested, but we don't * know how far we need to replay the WAL before we reach consistency. * This can happen for example if a base backup is taken from a * running server using an atomic filesystem snapshot, without calling * pg_start/stop_backup. Or if you just kill a running master server * and put it into archive recovery by creating a recovery signal * file. * * Our strategy in that case is to perform crash recovery first, * replaying all the WAL present in pg_wal, and only enter archive * recovery after that. * * But usually we already know how far we need to replay the WAL (up * to minRecoveryPoint, up to backupEndPoint, or until we see an * end-of-backup record), and we can enter archive recovery directly. */ if (ArchiveRecoveryRequested && (ControlFile->minRecoveryPoint != InvalidXLogRecPtr || ControlFile->backupEndRequired || ControlFile->backupEndPoint != InvalidXLogRecPtr || ControlFile->state == DB_SHUTDOWNED)) { InArchiveRecovery = true; if (StandbyModeRequested) StandbyMode = true; } /* Get the last valid checkpoint record. */ checkPointLoc = ControlFile->checkPoint; RedoStartLSN = ControlFile->checkPointCopy.redo; record = ReadCheckpointRecord(xlogreader, checkPointLoc, 1, true); if (record != NULL) { ereport(DEBUG1, (errmsg("checkpoint record is at %X/%X", (uint32) (checkPointLoc >> 32), (uint32) checkPointLoc))); } else { /* * We used to attempt to go back to a secondary checkpoint record * here, but only when not in standby mode. We now just fail if we * can't read the last checkpoint because this allows us to * simplify processing around checkpoints. */ ereport(PANIC, (errmsg("could not locate a valid checkpoint record"))); } memcpy(&checkPoint, XLogRecGetData(xlogreader), sizeof(CheckPoint)); wasShutdown = ((record->xl_info & ~XLR_INFO_MASK) == XLOG_CHECKPOINT_SHUTDOWN); } /* * Clear out any old relcache cache files. This is *necessary* if we do * any WAL replay, since that would probably result in the cache files * being out of sync with database reality. In theory we could leave them * in place if the database had been cleanly shut down, but it seems * safest to just remove them always and let them be rebuilt during the * first backend startup. These files needs to be removed from all * directories including pg_tblspc, however the symlinks are created only * after reading tablespace_map file in case of archive recovery from * backup, so needs to clear old relcache files here after creating * symlinks. */ RelationCacheInitFileRemove(); /* * If the location of the checkpoint record is not on the expected * timeline in the history of the requested timeline, we cannot proceed: * the backup is not part of the history of the requested timeline. */ Assert(expectedTLEs); /* was initialized by reading checkpoint * record */ if (tliOfPointInHistory(checkPointLoc, expectedTLEs) != checkPoint.ThisTimeLineID) { XLogRecPtr switchpoint; /* * tliSwitchPoint will throw an error if the checkpoint's timeline is * not in expectedTLEs at all. */ switchpoint = tliSwitchPoint(ControlFile->checkPointCopy.ThisTimeLineID, expectedTLEs, NULL); ereport(FATAL, (errmsg("requested timeline %u is not a child of this server's history", recoveryTargetTLI), errdetail("Latest checkpoint is at %X/%X on timeline %u, but in the history of the requested timeline, the server forked off from that timeline at %X/%X.", (uint32) (ControlFile->checkPoint >> 32), (uint32) ControlFile->checkPoint, ControlFile->checkPointCopy.ThisTimeLineID, (uint32) (switchpoint >> 32), (uint32) switchpoint))); } /* * The min recovery point should be part of the requested timeline's * history, too. */ if (!XLogRecPtrIsInvalid(ControlFile->minRecoveryPoint) && tliOfPointInHistory(ControlFile->minRecoveryPoint - 1, expectedTLEs) != ControlFile->minRecoveryPointTLI) ereport(FATAL, (errmsg("requested timeline %u does not contain minimum recovery point %X/%X on timeline %u", recoveryTargetTLI, (uint32) (ControlFile->minRecoveryPoint >> 32), (uint32) ControlFile->minRecoveryPoint, ControlFile->minRecoveryPointTLI))); LastRec = RecPtr = checkPointLoc; ereport(DEBUG1, (errmsg_internal("redo record is at %X/%X; shutdown %s", (uint32) (checkPoint.redo >> 32), (uint32) checkPoint.redo, wasShutdown ? "true" : "false"))); ereport(DEBUG1, (errmsg_internal("next transaction ID: " UINT64_FORMAT "; next OID: %u", U64FromFullTransactionId(checkPoint.nextFullXid), checkPoint.nextOid))); ereport(DEBUG1, (errmsg_internal("next MultiXactId: %u; next MultiXactOffset: %u", checkPoint.nextMulti, checkPoint.nextMultiOffset))); ereport(DEBUG1, (errmsg_internal("oldest unfrozen transaction ID: %u, in database %u", checkPoint.oldestXid, checkPoint.oldestXidDB))); ereport(DEBUG1, (errmsg_internal("oldest MultiXactId: %u, in database %u", checkPoint.oldestMulti, checkPoint.oldestMultiDB))); ereport(DEBUG1, (errmsg_internal("commit timestamp Xid oldest/newest: %u/%u", checkPoint.oldestCommitTsXid, checkPoint.newestCommitTsXid))); if (!TransactionIdIsNormal(XidFromFullTransactionId(checkPoint.nextFullXid))) ereport(PANIC, (errmsg("invalid next transaction ID"))); /* initialize shared memory variables from the checkpoint record */ ShmemVariableCache->nextFullXid = checkPoint.nextFullXid; ShmemVariableCache->nextOid = checkPoint.nextOid; ShmemVariableCache->oidCount = 0; MultiXactSetNextMXact(checkPoint.nextMulti, checkPoint.nextMultiOffset); AdvanceOldestClogXid(checkPoint.oldestXid); SetTransactionIdLimit(checkPoint.oldestXid, checkPoint.oldestXidDB); SetMultiXactIdLimit(checkPoint.oldestMulti, checkPoint.oldestMultiDB, true); SetCommitTsLimit(checkPoint.oldestCommitTsXid, checkPoint.newestCommitTsXid); XLogCtl->ckptFullXid = checkPoint.nextFullXid; /* * Initialize replication slots, before there's a chance to remove * required resources. */ StartupReplicationSlots(); /* * Startup logical state, needs to be setup now so we have proper data * during crash recovery. */ StartupReorderBuffer(); /* * Startup MultiXact. We need to do this early to be able to replay * truncations. */ StartupMultiXact(); /* * Ditto for commit timestamps. Activate the facility if the setting is * enabled in the control file, as there should be no tracking of commit * timestamps done when the setting was disabled. This facility can be * started or stopped when replaying a XLOG_PARAMETER_CHANGE record. */ if (ControlFile->track_commit_timestamp) StartupCommitTs(); /* * Recover knowledge about replay progress of known replication partners. */ StartupReplicationOrigin(); /* * Initialize unlogged LSN. On a clean shutdown, it's restored from the * control file. On recovery, all unlogged relations are blown away, so * the unlogged LSN counter can be reset too. */ if (ControlFile->state == DB_SHUTDOWNED) XLogCtl->unloggedLSN = ControlFile->unloggedLSN; else XLogCtl->unloggedLSN = FirstNormalUnloggedLSN; /* * We must replay WAL entries using the same TimeLineID they were created * under, so temporarily adopt the TLI indicated by the checkpoint (see * also xlog_redo()). */ ThisTimeLineID = checkPoint.ThisTimeLineID; /* * Copy any missing timeline history files between 'now' and the recovery * target timeline from archive to pg_wal. While we don't need those files * ourselves - the history file of the recovery target timeline covers all * the previous timelines in the history too - a cascading standby server * might be interested in them. Or, if you archive the WAL from this * server to a different archive than the master, it'd be good for all the * history files to get archived there after failover, so that you can use * one of the old timelines as a PITR target. Timeline history files are * small, so it's better to copy them unnecessarily than not copy them and * regret later. */ restoreTimeLineHistoryFiles(ThisTimeLineID, recoveryTargetTLI); /* * Before running in recovery, scan pg_twophase and fill in its status to * be able to work on entries generated by redo. Doing a scan before * taking any recovery action has the merit to discard any 2PC files that * are newer than the first record to replay, saving from any conflicts at * replay. This avoids as well any subsequent scans when doing recovery * of the on-disk two-phase data. */ restoreTwoPhaseData(); lastFullPageWrites = checkPoint.fullPageWrites; RedoRecPtr = XLogCtl->RedoRecPtr = XLogCtl->Insert.RedoRecPtr = checkPoint.redo; doPageWrites = lastFullPageWrites; if (RecPtr < checkPoint.redo) ereport(PANIC, (errmsg("invalid redo in checkpoint record"))); /* * Check whether we need to force recovery from WAL. If it appears to * have been a clean shutdown and we did not have a recovery signal file, * then assume no recovery needed. */ if (checkPoint.redo < RecPtr) { if (wasShutdown) ereport(PANIC, (errmsg("invalid redo record in shutdown checkpoint"))); InRecovery = true; } else if (ControlFile->state != DB_SHUTDOWNED) InRecovery = true; else if (ArchiveRecoveryRequested) { /* force recovery due to presence of recovery signal file */ InRecovery = true; } /* REDO */ if (InRecovery) { int rmid; /* * Update pg_control to show that we are recovering and to show the * selected checkpoint as the place we are starting from. We also mark * pg_control with any minimum recovery stop point obtained from a * backup history file. */ dbstate_at_startup = ControlFile->state; if (InArchiveRecovery) ControlFile->state = DB_IN_ARCHIVE_RECOVERY; else { ereport(LOG, (errmsg("database system was not properly shut down; " "automatic recovery in progress"))); if (recoveryTargetTLI > ControlFile->checkPointCopy.ThisTimeLineID) ereport(LOG, (errmsg("crash recovery starts in timeline %u " "and has target timeline %u", ControlFile->checkPointCopy.ThisTimeLineID, recoveryTargetTLI))); ControlFile->state = DB_IN_CRASH_RECOVERY; } ControlFile->checkPoint = checkPointLoc; ControlFile->checkPointCopy = checkPoint; if (InArchiveRecovery) { /* initialize minRecoveryPoint if not set yet */ if (ControlFile->minRecoveryPoint < checkPoint.redo) { ControlFile->minRecoveryPoint = checkPoint.redo; ControlFile->minRecoveryPointTLI = checkPoint.ThisTimeLineID; } } /* * Set backupStartPoint if we're starting recovery from a base backup. * * Also set backupEndPoint and use minRecoveryPoint as the backup end * location if we're starting recovery from a base backup which was * taken from a standby. In this case, the database system status in * pg_control must indicate that the database was already in recovery. * Usually that will be DB_IN_ARCHIVE_RECOVERY but also can be * DB_SHUTDOWNED_IN_RECOVERY if recovery previously was interrupted * before reaching this point; e.g. because restore_command or * primary_conninfo were faulty. * * Any other state indicates that the backup somehow became corrupted * and we can't sensibly continue with recovery. */ if (haveBackupLabel) { ControlFile->backupStartPoint = checkPoint.redo; ControlFile->backupEndRequired = backupEndRequired; if (backupFromStandby) { if (dbstate_at_startup != DB_IN_ARCHIVE_RECOVERY && dbstate_at_startup != DB_SHUTDOWNED_IN_RECOVERY) ereport(FATAL, (errmsg("backup_label contains data inconsistent with control file"), errhint("This means that the backup is corrupted and you will " "have to use another backup for recovery."))); ControlFile->backupEndPoint = ControlFile->minRecoveryPoint; } } ControlFile->time = (pg_time_t) time(NULL); /* No need to hold ControlFileLock yet, we aren't up far enough */ UpdateControlFile(); /* * Initialize our local copy of minRecoveryPoint. When doing crash * recovery we want to replay up to the end of WAL. Particularly, in * the case of a promoted standby minRecoveryPoint value in the * control file is only updated after the first checkpoint. However, * if the instance crashes before the first post-recovery checkpoint * is completed then recovery will use a stale location causing the * startup process to think that there are still invalid page * references when checking for data consistency. */ if (InArchiveRecovery) { minRecoveryPoint = ControlFile->minRecoveryPoint; minRecoveryPointTLI = ControlFile->minRecoveryPointTLI; } else { minRecoveryPoint = InvalidXLogRecPtr; minRecoveryPointTLI = 0; } /* * Reset pgstat data, because it may be invalid after recovery. */ pgstat_reset_all(); /* * If there was a backup label file, it's done its job and the info * has now been propagated into pg_control. We must get rid of the * label file so that if we crash during recovery, we'll pick up at * the latest recovery restartpoint instead of going all the way back * to the backup start point. It seems prudent though to just rename * the file out of the way rather than delete it completely. */ if (haveBackupLabel) { unlink(BACKUP_LABEL_OLD); durable_rename(BACKUP_LABEL_FILE, BACKUP_LABEL_OLD, FATAL); } /* * If there was a tablespace_map file, it's done its job and the * symlinks have been created. We must get rid of the map file so * that if we crash during recovery, we don't create symlinks again. * It seems prudent though to just rename the file out of the way * rather than delete it completely. */ if (haveTblspcMap) { unlink(TABLESPACE_MAP_OLD); durable_rename(TABLESPACE_MAP, TABLESPACE_MAP_OLD, FATAL); } /* Check that the GUCs used to generate the WAL allow recovery */ CheckRequiredParameterValues(); /* * We're in recovery, so unlogged relations may be trashed and must be * reset. This should be done BEFORE allowing Hot Standby * connections, so that read-only backends don't try to read whatever * garbage is left over from before. */ ResetUnloggedRelations(UNLOGGED_RELATION_CLEANUP); /* * Likewise, delete any saved transaction snapshot files that got left * behind by crashed backends. */ DeleteAllExportedSnapshotFiles(); /* * Initialize for Hot Standby, if enabled. We won't let backends in * yet, not until we've reached the min recovery point specified in * control file and we've established a recovery snapshot from a * running-xacts WAL record. */ if (ArchiveRecoveryRequested && EnableHotStandby) { TransactionId *xids; int nxids; ereport(DEBUG1, (errmsg("initializing for hot standby"))); InitRecoveryTransactionEnvironment(); if (wasShutdown) oldestActiveXID = PrescanPreparedTransactions(&xids, &nxids); else oldestActiveXID = checkPoint.oldestActiveXid; Assert(TransactionIdIsValid(oldestActiveXID)); /* Tell procarray about the range of xids it has to deal with */ ProcArrayInitRecovery(XidFromFullTransactionId(ShmemVariableCache->nextFullXid)); /* * Startup commit log and subtrans only. MultiXact and commit * timestamp have already been started up and other SLRUs are not * maintained during recovery and need not be started yet. */ StartupCLOG(); StartupSUBTRANS(oldestActiveXID); /* * If we're beginning at a shutdown checkpoint, we know that * nothing was running on the master at this point. So fake-up an * empty running-xacts record and use that here and now. Recover * additional standby state for prepared transactions. */ if (wasShutdown) { RunningTransactionsData running; TransactionId latestCompletedXid; /* * Construct a RunningTransactions snapshot representing a * shut down server, with only prepared transactions still * alive. We're never overflowed at this point because all * subxids are listed with their parent prepared transactions. */ running.xcnt = nxids; running.subxcnt = 0; running.subxid_overflow = false; running.nextXid = XidFromFullTransactionId(checkPoint.nextFullXid); running.oldestRunningXid = oldestActiveXID; latestCompletedXid = XidFromFullTransactionId(checkPoint.nextFullXid); TransactionIdRetreat(latestCompletedXid); Assert(TransactionIdIsNormal(latestCompletedXid)); running.latestCompletedXid = latestCompletedXid; running.xids = xids; ProcArrayApplyRecoveryInfo(&running); StandbyRecoverPreparedTransactions(); } } /* Initialize resource managers */ for (rmid = 0; rmid <= RM_MAX_ID; rmid++) { if (RmgrTable[rmid].rm_startup != NULL) RmgrTable[rmid].rm_startup(); } /* * Initialize shared variables for tracking progress of WAL replay, as * if we had just replayed the record before the REDO location (or the * checkpoint record itself, if it's a shutdown checkpoint). */ SpinLockAcquire(&XLogCtl->info_lck); if (checkPoint.redo < RecPtr) XLogCtl->replayEndRecPtr = checkPoint.redo; else XLogCtl->replayEndRecPtr = EndRecPtr; XLogCtl->replayEndTLI = ThisTimeLineID; XLogCtl->lastReplayedEndRecPtr = XLogCtl->replayEndRecPtr; XLogCtl->lastReplayedTLI = XLogCtl->replayEndTLI; XLogCtl->recoveryLastXTime = 0; XLogCtl->currentChunkStartTime = 0; XLogCtl->recoveryPause = false; SpinLockRelease(&XLogCtl->info_lck); /* Also ensure XLogReceiptTime has a sane value */ XLogReceiptTime = GetCurrentTimestamp(); /* * Let postmaster know we've started redo now, so that it can launch * checkpointer to perform restartpoints. We don't bother during * crash recovery as restartpoints can only be performed during * archive recovery. And we'd like to keep crash recovery simple, to * avoid introducing bugs that could affect you when recovering after * crash. * * After this point, we can no longer assume that we're the only * process in addition to postmaster! Also, fsync requests are * subsequently to be handled by the checkpointer, not locally. */ if (ArchiveRecoveryRequested && IsUnderPostmaster) { PublishStartupProcessInformation(); EnableSyncRequestForwarding(); SendPostmasterSignal(PMSIGNAL_RECOVERY_STARTED); bgwriterLaunched = true; } /* * Allow read-only connections immediately if we're consistent * already. */ CheckRecoveryConsistency(); /* * Find the first record that logically follows the checkpoint --- it * might physically precede it, though. */ if (checkPoint.redo < RecPtr) { /* back up to find the record */ XLogBeginRead(xlogreader, checkPoint.redo); record = ReadRecord(xlogreader, PANIC, false); } else { /* just have to read next record after CheckPoint */ record = ReadRecord(xlogreader, LOG, false); } if (record != NULL) { ErrorContextCallback errcallback; TimestampTz xtime; InRedo = true; ereport(LOG, (errmsg("redo starts at %X/%X", (uint32) (ReadRecPtr >> 32), (uint32) ReadRecPtr))); /* * main redo apply loop */ do { bool switchedTLI = false; #ifdef WAL_DEBUG if (XLOG_DEBUG || (rmid == RM_XACT_ID && trace_recovery_messages <= DEBUG2) || (rmid != RM_XACT_ID && trace_recovery_messages <= DEBUG3)) { StringInfoData buf; initStringInfo(&buf); appendStringInfo(&buf, "REDO @ %X/%X; LSN %X/%X: ", (uint32) (ReadRecPtr >> 32), (uint32) ReadRecPtr, (uint32) (EndRecPtr >> 32), (uint32) EndRecPtr); xlog_outrec(&buf, xlogreader); appendStringInfoString(&buf, " - "); xlog_outdesc(&buf, xlogreader); elog(LOG, "%s", buf.data); pfree(buf.data); } #endif /* Handle interrupt signals of startup process */ HandleStartupProcInterrupts(); /* * Pause WAL replay, if requested by a hot-standby session via * SetRecoveryPause(). * * Note that we intentionally don't take the info_lck spinlock * here. We might therefore read a slightly stale value of * the recoveryPause flag, but it can't be very stale (no * worse than the last spinlock we did acquire). Since a * pause request is a pretty asynchronous thing anyway, * possibly responding to it one WAL record later than we * otherwise would is a minor issue, so it doesn't seem worth * adding another spinlock cycle to prevent that. */ if (((volatile XLogCtlData *) XLogCtl)->recoveryPause) recoveryPausesHere(); /* * Have we reached our recovery target? */ if (recoveryStopsBefore(xlogreader)) { reachedStopPoint = true; /* see below */ break; } /* * If we've been asked to lag the master, wait on latch until * enough time has passed. */ if (recoveryApplyDelay(xlogreader)) { /* * We test for paused recovery again here. If user sets * delayed apply, it may be because they expect to pause * recovery in case of problems, so we must test again * here otherwise pausing during the delay-wait wouldn't * work. */ if (((volatile XLogCtlData *) XLogCtl)->recoveryPause) recoveryPausesHere(); } /* Setup error traceback support for ereport() */ errcallback.callback = rm_redo_error_callback; errcallback.arg = (void *) xlogreader; errcallback.previous = error_context_stack; error_context_stack = &errcallback; /* * ShmemVariableCache->nextFullXid must be beyond record's * xid. */ AdvanceNextFullTransactionIdPastXid(record->xl_xid); /* * Before replaying this record, check if this record causes * the current timeline to change. The record is already * considered to be part of the new timeline, so we update * ThisTimeLineID before replaying it. That's important so * that replayEndTLI, which is recorded as the minimum * recovery point's TLI if recovery stops after this record, * is set correctly. */ if (record->xl_rmid == RM_XLOG_ID) { TimeLineID newTLI = ThisTimeLineID; TimeLineID prevTLI = ThisTimeLineID; uint8 info = record->xl_info & ~XLR_INFO_MASK; if (info == XLOG_CHECKPOINT_SHUTDOWN) { CheckPoint checkPoint; memcpy(&checkPoint, XLogRecGetData(xlogreader), sizeof(CheckPoint)); newTLI = checkPoint.ThisTimeLineID; prevTLI = checkPoint.PrevTimeLineID; } else if (info == XLOG_END_OF_RECOVERY) { xl_end_of_recovery xlrec; memcpy(&xlrec, XLogRecGetData(xlogreader), sizeof(xl_end_of_recovery)); newTLI = xlrec.ThisTimeLineID; prevTLI = xlrec.PrevTimeLineID; } if (newTLI != ThisTimeLineID) { /* Check that it's OK to switch to this TLI */ checkTimeLineSwitch(EndRecPtr, newTLI, prevTLI); /* Following WAL records should be run with new TLI */ ThisTimeLineID = newTLI; switchedTLI = true; } } /* * Update shared replayEndRecPtr before replaying this record, * so that XLogFlush will update minRecoveryPoint correctly. */ SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->replayEndRecPtr = EndRecPtr; XLogCtl->replayEndTLI = ThisTimeLineID; SpinLockRelease(&XLogCtl->info_lck); /* * If we are attempting to enter Hot Standby mode, process * XIDs we see */ if (standbyState >= STANDBY_INITIALIZED && TransactionIdIsValid(record->xl_xid)) RecordKnownAssignedTransactionIds(record->xl_xid); /* Now apply the WAL record itself */ RmgrTable[record->xl_rmid].rm_redo(xlogreader); /* * After redo, check whether the backup pages associated with * the WAL record are consistent with the existing pages. This * check is done only if consistency check is enabled for this * record. */ if ((record->xl_info & XLR_CHECK_CONSISTENCY) != 0) checkXLogConsistency(xlogreader); /* Pop the error context stack */ error_context_stack = errcallback.previous; /* * Update lastReplayedEndRecPtr after this record has been * successfully replayed. */ SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->lastReplayedEndRecPtr = EndRecPtr; XLogCtl->lastReplayedTLI = ThisTimeLineID; SpinLockRelease(&XLogCtl->info_lck); /* * If rm_redo called XLogRequestWalReceiverReply, then we wake * up the receiver so that it notices the updated * lastReplayedEndRecPtr and sends a reply to the master. */ if (doRequestWalReceiverReply) { doRequestWalReceiverReply = false; WalRcvForceReply(); } /* Remember this record as the last-applied one */ LastRec = ReadRecPtr; /* Allow read-only connections if we're consistent now */ CheckRecoveryConsistency(); /* Is this a timeline switch? */ if (switchedTLI) { /* * Before we continue on the new timeline, clean up any * (possibly bogus) future WAL segments on the old * timeline. */ RemoveNonParentXlogFiles(EndRecPtr, ThisTimeLineID); /* * Wake up any walsenders to notice that we are on a new * timeline. */ if (switchedTLI && AllowCascadeReplication()) WalSndWakeup(); } /* Exit loop if we reached inclusive recovery target */ if (recoveryStopsAfter(xlogreader)) { reachedStopPoint = true; break; } /* Else, try to fetch the next WAL record */ record = ReadRecord(xlogreader, LOG, false); } while (record != NULL); /* * end of main redo apply loop */ if (reachedStopPoint) { if (!reachedConsistency) ereport(FATAL, (errmsg("requested recovery stop point is before consistent recovery point"))); /* * This is the last point where we can restart recovery with a * new recovery target, if we shutdown and begin again. After * this, Resource Managers may choose to do permanent * corrective actions at end of recovery. */ switch (recoveryTargetAction) { case RECOVERY_TARGET_ACTION_SHUTDOWN: /* * exit with special return code to request shutdown * of postmaster. Log messages issued from * postmaster. */ proc_exit(3); case RECOVERY_TARGET_ACTION_PAUSE: SetRecoveryPause(true); recoveryPausesHere(); /* drop into promote */ case RECOVERY_TARGET_ACTION_PROMOTE: break; } } /* Allow resource managers to do any required cleanup. */ for (rmid = 0; rmid <= RM_MAX_ID; rmid++) { if (RmgrTable[rmid].rm_cleanup != NULL) RmgrTable[rmid].rm_cleanup(); } ereport(LOG, (errmsg("redo done at %X/%X", (uint32) (ReadRecPtr >> 32), (uint32) ReadRecPtr))); xtime = GetLatestXTime(); if (xtime) ereport(LOG, (errmsg("last completed transaction was at log time %s", timestamptz_to_str(xtime)))); InRedo = false; } else { /* there are no WAL records following the checkpoint */ ereport(LOG, (errmsg("redo is not required"))); } } /* * Kill WAL receiver, if it's still running, before we continue to write * the startup checkpoint record. It will trump over the checkpoint and * subsequent records if it's still alive when we start writing WAL. */ ShutdownWalRcv(); /* * Reset unlogged relations to the contents of their INIT fork. This is * done AFTER recovery is complete so as to include any unlogged relations * created during recovery, but BEFORE recovery is marked as having * completed successfully. Otherwise we'd not retry if any of the post * end-of-recovery steps fail. */ if (InRecovery) ResetUnloggedRelations(UNLOGGED_RELATION_INIT); /* * We don't need the latch anymore. It's not strictly necessary to disown * it, but let's do it for the sake of tidiness. */ if (ArchiveRecoveryRequested) DisownLatch(&XLogCtl->recoveryWakeupLatch); /* * We are now done reading the xlog from stream. Turn off streaming * recovery to force fetching the files (which would be required at end of * recovery, e.g., timeline history file) from archive or pg_wal. */ StandbyMode = false; /* * Re-fetch the last valid or last applied record, so we can identify the * exact endpoint of what we consider the valid portion of WAL. */ XLogBeginRead(xlogreader, LastRec); record = ReadRecord(xlogreader, PANIC, false); EndOfLog = EndRecPtr; /* * EndOfLogTLI is the TLI in the filename of the XLOG segment containing * the end-of-log. It could be different from the timeline that EndOfLog * nominally belongs to, if there was a timeline switch in that segment, * and we were reading the old WAL from a segment belonging to a higher * timeline. */ EndOfLogTLI = xlogreader->seg.ws_tli; /* * Complain if we did not roll forward far enough to render the backup * dump consistent. Note: it is indeed okay to look at the local variable * minRecoveryPoint here, even though ControlFile->minRecoveryPoint might * be further ahead --- ControlFile->minRecoveryPoint cannot have been * advanced beyond the WAL we processed. */ if (InRecovery && (EndOfLog < minRecoveryPoint || !XLogRecPtrIsInvalid(ControlFile->backupStartPoint))) { /* * Ran off end of WAL before reaching end-of-backup WAL record, or * minRecoveryPoint. That's usually a bad sign, indicating that you * tried to recover from an online backup but never called * pg_stop_backup(), or you didn't archive all the WAL up to that * point. However, this also happens in crash recovery, if the system * crashes while an online backup is in progress. We must not treat * that as an error, or the database will refuse to start up. */ if (ArchiveRecoveryRequested || ControlFile->backupEndRequired) { if (ControlFile->backupEndRequired) ereport(FATAL, (errmsg("WAL ends before end of online backup"), errhint("All WAL generated while online backup was taken must be available at recovery."))); else if (!XLogRecPtrIsInvalid(ControlFile->backupStartPoint)) ereport(FATAL, (errmsg("WAL ends before end of online backup"), errhint("Online backup started with pg_start_backup() must be ended with pg_stop_backup(), and all WAL up to that point must be available at recovery."))); else ereport(FATAL, (errmsg("WAL ends before consistent recovery point"))); } } /* * Pre-scan prepared transactions to find out the range of XIDs present. * This information is not quite needed yet, but it is positioned here so * as potential problems are detected before any on-disk change is done. */ oldestActiveXID = PrescanPreparedTransactions(NULL, NULL); /* * Consider whether we need to assign a new timeline ID. * * If we are doing an archive recovery, we always assign a new ID. This * handles a couple of issues. If we stopped short of the end of WAL * during recovery, then we are clearly generating a new timeline and must * assign it a unique new ID. Even if we ran to the end, modifying the * current last segment is problematic because it may result in trying to * overwrite an already-archived copy of that segment, and we encourage * DBAs to make their archive_commands reject that. We can dodge the * problem by making the new active segment have a new timeline ID. * * In a normal crash recovery, we can just extend the timeline we were in. */ PrevTimeLineID = ThisTimeLineID; if (ArchiveRecoveryRequested) { char reason[200]; char recoveryPath[MAXPGPATH]; Assert(InArchiveRecovery); ThisTimeLineID = findNewestTimeLine(recoveryTargetTLI) + 1; ereport(LOG, (errmsg("selected new timeline ID: %u", ThisTimeLineID))); /* * Create a comment for the history file to explain why and where * timeline changed. */ if (recoveryTarget == RECOVERY_TARGET_XID) snprintf(reason, sizeof(reason), "%s transaction %u", recoveryStopAfter ? "after" : "before", recoveryStopXid); else if (recoveryTarget == RECOVERY_TARGET_TIME) snprintf(reason, sizeof(reason), "%s %s\n", recoveryStopAfter ? "after" : "before", timestamptz_to_str(recoveryStopTime)); else if (recoveryTarget == RECOVERY_TARGET_LSN) snprintf(reason, sizeof(reason), "%s LSN %X/%X\n", recoveryStopAfter ? "after" : "before", (uint32) (recoveryStopLSN >> 32), (uint32) recoveryStopLSN); else if (recoveryTarget == RECOVERY_TARGET_NAME) snprintf(reason, sizeof(reason), "at restore point \"%s\"", recoveryStopName); else if (recoveryTarget == RECOVERY_TARGET_IMMEDIATE) snprintf(reason, sizeof(reason), "reached consistency"); else snprintf(reason, sizeof(reason), "no recovery target specified"); /* * We are now done reading the old WAL. Turn off archive fetching if * it was active, and make a writable copy of the last WAL segment. * (Note that we also have a copy of the last block of the old WAL in * readBuf; we will use that below.) */ exitArchiveRecovery(EndOfLogTLI, EndOfLog); /* * Write the timeline history file, and have it archived. After this * point (or rather, as soon as the file is archived), the timeline * will appear as "taken" in the WAL archive and to any standby * servers. If we crash before actually switching to the new * timeline, standby servers will nevertheless think that we switched * to the new timeline, and will try to connect to the new timeline. * To minimize the window for that, try to do as little as possible * between here and writing the end-of-recovery record. */ writeTimeLineHistory(ThisTimeLineID, recoveryTargetTLI, EndRecPtr, reason); /* * Since there might be a partial WAL segment named RECOVERYXLOG, get * rid of it. */ snprintf(recoveryPath, MAXPGPATH, XLOGDIR "/RECOVERYXLOG"); unlink(recoveryPath); /* ignore any error */ /* Get rid of any remaining recovered timeline-history file, too */ snprintf(recoveryPath, MAXPGPATH, XLOGDIR "/RECOVERYHISTORY"); unlink(recoveryPath); /* ignore any error */ } /* Save the selected TimeLineID in shared memory, too */ XLogCtl->ThisTimeLineID = ThisTimeLineID; XLogCtl->PrevTimeLineID = PrevTimeLineID; /* * Prepare to write WAL starting at EndOfLog location, and init xlog * buffer cache using the block containing the last record from the * previous incarnation. */ Insert = &XLogCtl->Insert; Insert->PrevBytePos = XLogRecPtrToBytePos(LastRec); Insert->CurrBytePos = XLogRecPtrToBytePos(EndOfLog); /* * Tricky point here: readBuf contains the *last* block that the LastRec * record spans, not the one it starts in. The last block is indeed the * one we want to use. */ if (EndOfLog % XLOG_BLCKSZ != 0) { char *page; int len; int firstIdx; XLogRecPtr pageBeginPtr; pageBeginPtr = EndOfLog - (EndOfLog % XLOG_BLCKSZ); Assert(readOff == XLogSegmentOffset(pageBeginPtr, wal_segment_size)); firstIdx = XLogRecPtrToBufIdx(EndOfLog); /* Copy the valid part of the last block, and zero the rest */ page = &XLogCtl->pages[firstIdx * XLOG_BLCKSZ]; len = EndOfLog % XLOG_BLCKSZ; memcpy(page, xlogreader->readBuf, len); memset(page + len, 0, XLOG_BLCKSZ - len); XLogCtl->xlblocks[firstIdx] = pageBeginPtr + XLOG_BLCKSZ; XLogCtl->InitializedUpTo = pageBeginPtr + XLOG_BLCKSZ; } else { /* * There is no partial block to copy. Just set InitializedUpTo, and * let the first attempt to insert a log record to initialize the next * buffer. */ XLogCtl->InitializedUpTo = EndOfLog; } LogwrtResult.Write = LogwrtResult.Flush = EndOfLog; XLogCtl->LogwrtResult = LogwrtResult; XLogCtl->LogwrtRqst.Write = EndOfLog; XLogCtl->LogwrtRqst.Flush = EndOfLog; /* * Update full_page_writes in shared memory and write an XLOG_FPW_CHANGE * record before resource manager writes cleanup WAL records or checkpoint * record is written. */ Insert->fullPageWrites = lastFullPageWrites; LocalSetXLogInsertAllowed(); UpdateFullPageWrites(); LocalXLogInsertAllowed = -1; if (InRecovery) { /* * Perform a checkpoint to update all our recovery activity to disk. * * Note that we write a shutdown checkpoint rather than an on-line * one. This is not particularly critical, but since we may be * assigning a new TLI, using a shutdown checkpoint allows us to have * the rule that TLI only changes in shutdown checkpoints, which * allows some extra error checking in xlog_redo. * * In fast promotion, only create a lightweight end-of-recovery record * instead of a full checkpoint. A checkpoint is requested later, * after we're fully out of recovery mode and already accepting * queries. */ if (bgwriterLaunched) { if (fast_promote) { checkPointLoc = ControlFile->checkPoint; /* * Confirm the last checkpoint is available for us to recover * from if we fail. */ record = ReadCheckpointRecord(xlogreader, checkPointLoc, 1, false); if (record != NULL) { fast_promoted = true; /* * Insert a special WAL record to mark the end of * recovery, since we aren't doing a checkpoint. That * means that the checkpointer process may likely be in * the middle of a time-smoothed restartpoint and could * continue to be for minutes after this. That sounds * strange, but the effect is roughly the same and it * would be stranger to try to come out of the * restartpoint and then checkpoint. We request a * checkpoint later anyway, just for safety. */ CreateEndOfRecoveryRecord(); } } if (!fast_promoted) RequestCheckpoint(CHECKPOINT_END_OF_RECOVERY | CHECKPOINT_IMMEDIATE | CHECKPOINT_WAIT); } else CreateCheckPoint(CHECKPOINT_END_OF_RECOVERY | CHECKPOINT_IMMEDIATE); } if (ArchiveRecoveryRequested) { /* * And finally, execute the recovery_end_command, if any. */ if (recoveryEndCommand && strcmp(recoveryEndCommand, "") != 0) ExecuteRecoveryCommand(recoveryEndCommand, "recovery_end_command", true); /* * We switched to a new timeline. Clean up segments on the old * timeline. * * If there are any higher-numbered segments on the old timeline, * remove them. They might contain valid WAL, but they might also be * pre-allocated files containing garbage. In any case, they are not * part of the new timeline's history so we don't need them. */ RemoveNonParentXlogFiles(EndOfLog, ThisTimeLineID); /* * If the switch happened in the middle of a segment, what to do with * the last, partial segment on the old timeline? If we don't archive * it, and the server that created the WAL never archives it either * (e.g. because it was hit by a meteor), it will never make it to the * archive. That's OK from our point of view, because the new segment * that we created with the new TLI contains all the WAL from the old * timeline up to the switch point. But if you later try to do PITR to * the "missing" WAL on the old timeline, recovery won't find it in * the archive. It's physically present in the new file with new TLI, * but recovery won't look there when it's recovering to the older * timeline. On the other hand, if we archive the partial segment, and * the original server on that timeline is still running and archives * the completed version of the same segment later, it will fail. (We * used to do that in 9.4 and below, and it caused such problems). * * As a compromise, we rename the last segment with the .partial * suffix, and archive it. Archive recovery will never try to read * .partial segments, so they will normally go unused. But in the odd * PITR case, the administrator can copy them manually to the pg_wal * directory (removing the suffix). They can be useful in debugging, * too. * * If a .done or .ready file already exists for the old timeline, * however, we had already determined that the segment is complete, so * we can let it be archived normally. (In particular, if it was * restored from the archive to begin with, it's expected to have a * .done file). */ if (XLogSegmentOffset(EndOfLog, wal_segment_size) != 0 && XLogArchivingActive()) { char origfname[MAXFNAMELEN]; XLogSegNo endLogSegNo; XLByteToPrevSeg(EndOfLog, endLogSegNo, wal_segment_size); XLogFileName(origfname, EndOfLogTLI, endLogSegNo, wal_segment_size); if (!XLogArchiveIsReadyOrDone(origfname)) { char origpath[MAXPGPATH]; char partialfname[MAXFNAMELEN]; char partialpath[MAXPGPATH]; XLogFilePath(origpath, EndOfLogTLI, endLogSegNo, wal_segment_size); snprintf(partialfname, MAXFNAMELEN, "%s.partial", origfname); snprintf(partialpath, MAXPGPATH, "%s.partial", origpath); /* * Make sure there's no .done or .ready file for the .partial * file. */ XLogArchiveCleanup(partialfname); durable_rename(origpath, partialpath, ERROR); XLogArchiveNotify(partialfname); } } } /* * Preallocate additional log files, if wanted. */ PreallocXlogFiles(EndOfLog); /* * Okay, we're officially UP. */ InRecovery = false; /* start the archive_timeout timer and LSN running */ XLogCtl->lastSegSwitchTime = (pg_time_t) time(NULL); XLogCtl->lastSegSwitchLSN = EndOfLog; /* also initialize latestCompletedXid, to nextXid - 1 */ LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE); ShmemVariableCache->latestCompletedXid = XidFromFullTransactionId(ShmemVariableCache->nextFullXid); TransactionIdRetreat(ShmemVariableCache->latestCompletedXid); LWLockRelease(ProcArrayLock); /* * Start up the commit log and subtrans, if not already done for hot * standby. (commit timestamps are started below, if necessary.) */ if (standbyState == STANDBY_DISABLED) { StartupCLOG(); StartupSUBTRANS(oldestActiveXID); } /* * Perform end of recovery actions for any SLRUs that need it. */ TrimCLOG(); TrimMultiXact(); /* Reload shared-memory state for prepared transactions */ RecoverPreparedTransactions(); /* * Shutdown the recovery environment. This must occur after * RecoverPreparedTransactions(), see notes for lock_twophase_recover() */ if (standbyState != STANDBY_DISABLED) ShutdownRecoveryTransactionEnvironment(); /* Shut down xlogreader */ if (readFile >= 0) { close(readFile); readFile = -1; } XLogReaderFree(xlogreader); /* * If any of the critical GUCs have changed, log them before we allow * backends to write WAL. */ LocalSetXLogInsertAllowed(); XLogReportParameters(); /* * Local WAL inserts enabled, so it's time to finish initialization of * commit timestamp. */ CompleteCommitTsInitialization(); /* * All done with end-of-recovery actions. * * Now allow backends to write WAL and update the control file status in * consequence. The boolean flag allowing backends to write WAL is * updated while holding ControlFileLock to prevent other backends to look * at an inconsistent state of the control file in shared memory. There * is still a small window during which backends can write WAL and the * control file is still referring to a system not in DB_IN_PRODUCTION * state while looking at the on-disk control file. * * Also, although the boolean flag to allow WAL is probably atomic in * itself, we use the info_lck here to ensure that there are no race * conditions concerning visibility of other recent updates to shared * memory. */ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); ControlFile->state = DB_IN_PRODUCTION; ControlFile->time = (pg_time_t) time(NULL); SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->SharedRecoveryInProgress = false; SpinLockRelease(&XLogCtl->info_lck); UpdateControlFile(); LWLockRelease(ControlFileLock); /* * If there were cascading standby servers connected to us, nudge any wal * sender processes to notice that we've been promoted. */ WalSndWakeup(); /* * If this was a fast promotion, request an (online) checkpoint now. This * isn't required for consistency, but the last restartpoint might be far * back, and in case of a crash, recovering from it might take a longer * than is appropriate now that we're not in standby mode anymore. */ if (fast_promoted) RequestCheckpoint(CHECKPOINT_FORCE); } /* * Checks if recovery has reached a consistent state. When consistency is * reached and we have a valid starting standby snapshot, tell postmaster * that it can start accepting read-only connections. */ static void CheckRecoveryConsistency(void) { XLogRecPtr lastReplayedEndRecPtr; /* * During crash recovery, we don't reach a consistent state until we've * replayed all the WAL. */ if (XLogRecPtrIsInvalid(minRecoveryPoint)) return; Assert(InArchiveRecovery); /* * assume that we are called in the startup process, and hence don't need * a lock to read lastReplayedEndRecPtr */ lastReplayedEndRecPtr = XLogCtl->lastReplayedEndRecPtr; /* * Have we reached the point where our base backup was completed? */ if (!XLogRecPtrIsInvalid(ControlFile->backupEndPoint) && ControlFile->backupEndPoint <= lastReplayedEndRecPtr) { /* * We have reached the end of base backup, as indicated by pg_control. * The data on disk is now consistent. Reset backupStartPoint and * backupEndPoint, and update minRecoveryPoint to make sure we don't * allow starting up at an earlier point even if recovery is stopped * and restarted soon after this. */ elog(DEBUG1, "end of backup reached"); LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); if (ControlFile->minRecoveryPoint < lastReplayedEndRecPtr) ControlFile->minRecoveryPoint = lastReplayedEndRecPtr; ControlFile->backupStartPoint = InvalidXLogRecPtr; ControlFile->backupEndPoint = InvalidXLogRecPtr; ControlFile->backupEndRequired = false; UpdateControlFile(); LWLockRelease(ControlFileLock); } /* * Have we passed our safe starting point? Note that minRecoveryPoint is * known to be incorrectly set if ControlFile->backupEndRequired, until * the XLOG_BACKUP_END arrives to advise us of the correct * minRecoveryPoint. All we know prior to that is that we're not * consistent yet. */ if (!reachedConsistency && !ControlFile->backupEndRequired && minRecoveryPoint <= lastReplayedEndRecPtr && XLogRecPtrIsInvalid(ControlFile->backupStartPoint)) { /* * Check to see if the XLOG sequence contained any unresolved * references to uninitialized pages. */ XLogCheckInvalidPages(); reachedConsistency = true; ereport(LOG, (errmsg("consistent recovery state reached at %X/%X", (uint32) (lastReplayedEndRecPtr >> 32), (uint32) lastReplayedEndRecPtr))); } /* * Have we got a valid starting snapshot that will allow queries to be * run? If so, we can tell postmaster that the database is consistent now, * enabling connections. */ if (standbyState == STANDBY_SNAPSHOT_READY && !LocalHotStandbyActive && reachedConsistency && IsUnderPostmaster) { SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->SharedHotStandbyActive = true; SpinLockRelease(&XLogCtl->info_lck); LocalHotStandbyActive = true; SendPostmasterSignal(PMSIGNAL_BEGIN_HOT_STANDBY); } } /* * Is the system still in recovery? * * Unlike testing InRecovery, this works in any process that's connected to * shared memory. * * As a side-effect, we initialize the local TimeLineID and RedoRecPtr * variables the first time we see that recovery is finished. */ bool RecoveryInProgress(void) { /* * We check shared state each time only until we leave recovery mode. We * can't re-enter recovery, so there's no need to keep checking after the * shared variable has once been seen false. */ if (!LocalRecoveryInProgress) return false; else { /* * use volatile pointer to make sure we make a fresh read of the * shared variable. */ volatile XLogCtlData *xlogctl = XLogCtl; LocalRecoveryInProgress = xlogctl->SharedRecoveryInProgress; /* * Initialize TimeLineID and RedoRecPtr when we discover that recovery * is finished. InitPostgres() relies upon this behaviour to ensure * that InitXLOGAccess() is called at backend startup. (If you change * this, see also LocalSetXLogInsertAllowed.) */ if (!LocalRecoveryInProgress) { /* * If we just exited recovery, make sure we read TimeLineID and * RedoRecPtr after SharedRecoveryInProgress (for machines with * weak memory ordering). */ pg_memory_barrier(); InitXLOGAccess(); } /* * Note: We don't need a memory barrier when we're still in recovery. * We might exit recovery immediately after return, so the caller * can't rely on 'true' meaning that we're still in recovery anyway. */ return LocalRecoveryInProgress; } } /* * Is HotStandby active yet? This is only important in special backends * since normal backends won't ever be able to connect until this returns * true. Postmaster knows this by way of signal, not via shared memory. * * Unlike testing standbyState, this works in any process that's connected to * shared memory. (And note that standbyState alone doesn't tell the truth * anyway.) */ bool HotStandbyActive(void) { /* * We check shared state each time only until Hot Standby is active. We * can't de-activate Hot Standby, so there's no need to keep checking * after the shared variable has once been seen true. */ if (LocalHotStandbyActive) return true; else { /* spinlock is essential on machines with weak memory ordering! */ SpinLockAcquire(&XLogCtl->info_lck); LocalHotStandbyActive = XLogCtl->SharedHotStandbyActive; SpinLockRelease(&XLogCtl->info_lck); return LocalHotStandbyActive; } } /* * Like HotStandbyActive(), but to be used only in WAL replay code, * where we don't need to ask any other process what the state is. */ bool HotStandbyActiveInReplay(void) { Assert(AmStartupProcess() || !IsPostmasterEnvironment); return LocalHotStandbyActive; } /* * Is this process allowed to insert new WAL records? * * Ordinarily this is essentially equivalent to !RecoveryInProgress(). * But we also have provisions for forcing the result "true" or "false" * within specific processes regardless of the global state. */ bool XLogInsertAllowed(void) { /* * If value is "unconditionally true" or "unconditionally false", just * return it. This provides the normal fast path once recovery is known * done. */ if (LocalXLogInsertAllowed >= 0) return (bool) LocalXLogInsertAllowed; /* * Else, must check to see if we're still in recovery. */ if (RecoveryInProgress()) return false; /* * On exit from recovery, reset to "unconditionally true", since there is * no need to keep checking. */ LocalXLogInsertAllowed = 1; return true; } /* * Make XLogInsertAllowed() return true in the current process only. * * Note: it is allowed to switch LocalXLogInsertAllowed back to -1 later, * and even call LocalSetXLogInsertAllowed() again after that. */ static void LocalSetXLogInsertAllowed(void) { Assert(LocalXLogInsertAllowed == -1); LocalXLogInsertAllowed = 1; /* Initialize as RecoveryInProgress() would do when switching state */ InitXLOGAccess(); } /* * Subroutine to try to fetch and validate a prior checkpoint record. * * whichChkpt identifies the checkpoint (merely for reporting purposes). * 1 for "primary", 0 for "other" (backup_label) */ static XLogRecord * ReadCheckpointRecord(XLogReaderState *xlogreader, XLogRecPtr RecPtr, int whichChkpt, bool report) { XLogRecord *record; uint8 info; if (!XRecOffIsValid(RecPtr)) { if (!report) return NULL; switch (whichChkpt) { case 1: ereport(LOG, (errmsg("invalid primary checkpoint link in control file"))); break; default: ereport(LOG, (errmsg("invalid checkpoint link in backup_label file"))); break; } return NULL; } XLogBeginRead(xlogreader, RecPtr); record = ReadRecord(xlogreader, LOG, true); if (record == NULL) { if (!report) return NULL; switch (whichChkpt) { case 1: ereport(LOG, (errmsg("invalid primary checkpoint record"))); break; default: ereport(LOG, (errmsg("invalid checkpoint record"))); break; } return NULL; } if (record->xl_rmid != RM_XLOG_ID) { switch (whichChkpt) { case 1: ereport(LOG, (errmsg("invalid resource manager ID in primary checkpoint record"))); break; default: ereport(LOG, (errmsg("invalid resource manager ID in checkpoint record"))); break; } return NULL; } info = record->xl_info & ~XLR_INFO_MASK; if (info != XLOG_CHECKPOINT_SHUTDOWN && info != XLOG_CHECKPOINT_ONLINE) { switch (whichChkpt) { case 1: ereport(LOG, (errmsg("invalid xl_info in primary checkpoint record"))); break; default: ereport(LOG, (errmsg("invalid xl_info in checkpoint record"))); break; } return NULL; } if (record->xl_tot_len != SizeOfXLogRecord + SizeOfXLogRecordDataHeaderShort + sizeof(CheckPoint)) { switch (whichChkpt) { case 1: ereport(LOG, (errmsg("invalid length of primary checkpoint record"))); break; default: ereport(LOG, (errmsg("invalid length of checkpoint record"))); break; } return NULL; } return record; } /* * This must be called in a backend process before creating WAL records * (except in a standalone backend, which does StartupXLOG instead). We need * to initialize the local copies of ThisTimeLineID and RedoRecPtr. * * Note: before Postgres 8.0, we went to some effort to keep the postmaster * process's copies of ThisTimeLineID and RedoRecPtr valid too. This was * unnecessary however, since the postmaster itself never touches XLOG anyway. */ void InitXLOGAccess(void) { XLogCtlInsert *Insert = &XLogCtl->Insert; /* ThisTimeLineID doesn't change so we need no lock to copy it */ ThisTimeLineID = XLogCtl->ThisTimeLineID; Assert(ThisTimeLineID != 0 || IsBootstrapProcessingMode()); /* set wal_segment_size */ wal_segment_size = ControlFile->xlog_seg_size; /* Use GetRedoRecPtr to copy the RedoRecPtr safely */ (void) GetRedoRecPtr(); /* Also update our copy of doPageWrites. */ doPageWrites = (Insert->fullPageWrites || Insert->forcePageWrites); /* Also initialize the working areas for constructing WAL records */ InitXLogInsert(); } /* * Return the current Redo pointer from shared memory. * * As a side-effect, the local RedoRecPtr copy is updated. */ XLogRecPtr GetRedoRecPtr(void) { XLogRecPtr ptr; /* * The possibly not up-to-date copy in XlogCtl is enough. Even if we * grabbed a WAL insertion lock to read the master copy, someone might * update it just after we've released the lock. */ SpinLockAcquire(&XLogCtl->info_lck); ptr = XLogCtl->RedoRecPtr; SpinLockRelease(&XLogCtl->info_lck); if (RedoRecPtr < ptr) RedoRecPtr = ptr; return RedoRecPtr; } /* * Return information needed to decide whether a modified block needs a * full-page image to be included in the WAL record. * * The returned values are cached copies from backend-private memory, and * possibly out-of-date. XLogInsertRecord will re-check them against * up-to-date values, while holding the WAL insert lock. */ void GetFullPageWriteInfo(XLogRecPtr *RedoRecPtr_p, bool *doPageWrites_p) { *RedoRecPtr_p = RedoRecPtr; *doPageWrites_p = doPageWrites; } /* * GetInsertRecPtr -- Returns the current insert position. * * NOTE: The value *actually* returned is the position of the last full * xlog page. It lags behind the real insert position by at most 1 page. * For that, we don't need to scan through WAL insertion locks, and an * approximation is enough for the current usage of this function. */ XLogRecPtr GetInsertRecPtr(void) { XLogRecPtr recptr; SpinLockAcquire(&XLogCtl->info_lck); recptr = XLogCtl->LogwrtRqst.Write; SpinLockRelease(&XLogCtl->info_lck); return recptr; } /* * GetFlushRecPtr -- Returns the current flush position, ie, the last WAL * position known to be fsync'd to disk. */ XLogRecPtr GetFlushRecPtr(void) { SpinLockAcquire(&XLogCtl->info_lck); LogwrtResult = XLogCtl->LogwrtResult; SpinLockRelease(&XLogCtl->info_lck); return LogwrtResult.Flush; } /* * GetLastImportantRecPtr -- Returns the LSN of the last important record * inserted. All records not explicitly marked as unimportant are considered * important. * * The LSN is determined by computing the maximum of * WALInsertLocks[i].lastImportantAt. */ XLogRecPtr GetLastImportantRecPtr(void) { XLogRecPtr res = InvalidXLogRecPtr; int i; for (i = 0; i < NUM_XLOGINSERT_LOCKS; i++) { XLogRecPtr last_important; /* * Need to take a lock to prevent torn reads of the LSN, which are * possible on some of the supported platforms. WAL insert locks only * support exclusive mode, so we have to use that. */ LWLockAcquire(&WALInsertLocks[i].l.lock, LW_EXCLUSIVE); last_important = WALInsertLocks[i].l.lastImportantAt; LWLockRelease(&WALInsertLocks[i].l.lock); if (res < last_important) res = last_important; } return res; } /* * Get the time and LSN of the last xlog segment switch */ pg_time_t GetLastSegSwitchData(XLogRecPtr *lastSwitchLSN) { pg_time_t result; /* Need WALWriteLock, but shared lock is sufficient */ LWLockAcquire(WALWriteLock, LW_SHARED); result = XLogCtl->lastSegSwitchTime; *lastSwitchLSN = XLogCtl->lastSegSwitchLSN; LWLockRelease(WALWriteLock); return result; } /* * This must be called ONCE during postmaster or standalone-backend shutdown */ void ShutdownXLOG(int code, Datum arg) { /* * We should have an aux process resource owner to use, and we should not * be in a transaction that's installed some other resowner. */ Assert(AuxProcessResourceOwner != NULL); Assert(CurrentResourceOwner == NULL || CurrentResourceOwner == AuxProcessResourceOwner); CurrentResourceOwner = AuxProcessResourceOwner; /* Don't be chatty in standalone mode */ ereport(IsPostmasterEnvironment ? LOG : NOTICE, (errmsg("shutting down"))); /* * Signal walsenders to move to stopping state. */ WalSndInitStopping(); /* * Wait for WAL senders to be in stopping state. This prevents commands * from writing new WAL. */ WalSndWaitStopping(); if (RecoveryInProgress()) CreateRestartPoint(CHECKPOINT_IS_SHUTDOWN | CHECKPOINT_IMMEDIATE); else { /* * If archiving is enabled, rotate the last XLOG file so that all the * remaining records are archived (postmaster wakes up the archiver * process one more time at the end of shutdown). The checkpoint * record will go to the next XLOG file and won't be archived (yet). */ if (XLogArchivingActive() && XLogArchiveCommandSet()) RequestXLogSwitch(false); CreateCheckPoint(CHECKPOINT_IS_SHUTDOWN | CHECKPOINT_IMMEDIATE); } ShutdownCLOG(); ShutdownCommitTs(); ShutdownSUBTRANS(); ShutdownMultiXact(); } /* * Log start of a checkpoint. */ static void LogCheckpointStart(int flags, bool restartpoint) { elog(LOG, "%s starting:%s%s%s%s%s%s%s%s", restartpoint ? "restartpoint" : "checkpoint", (flags & CHECKPOINT_IS_SHUTDOWN) ? " shutdown" : "", (flags & CHECKPOINT_END_OF_RECOVERY) ? " end-of-recovery" : "", (flags & CHECKPOINT_IMMEDIATE) ? " immediate" : "", (flags & CHECKPOINT_FORCE) ? " force" : "", (flags & CHECKPOINT_WAIT) ? " wait" : "", (flags & CHECKPOINT_CAUSE_XLOG) ? " wal" : "", (flags & CHECKPOINT_CAUSE_TIME) ? " time" : "", (flags & CHECKPOINT_FLUSH_ALL) ? " flush-all" : ""); } /* * Log end of a checkpoint. */ static void LogCheckpointEnd(bool restartpoint) { long write_secs, sync_secs, total_secs, longest_secs, average_secs; int write_usecs, sync_usecs, total_usecs, longest_usecs, average_usecs; uint64 average_sync_time; CheckpointStats.ckpt_end_t = GetCurrentTimestamp(); TimestampDifference(CheckpointStats.ckpt_write_t, CheckpointStats.ckpt_sync_t, &write_secs, &write_usecs); TimestampDifference(CheckpointStats.ckpt_sync_t, CheckpointStats.ckpt_sync_end_t, &sync_secs, &sync_usecs); /* Accumulate checkpoint timing summary data, in milliseconds. */ BgWriterStats.m_checkpoint_write_time += write_secs * 1000 + write_usecs / 1000; BgWriterStats.m_checkpoint_sync_time += sync_secs * 1000 + sync_usecs / 1000; /* * All of the published timing statistics are accounted for. Only * continue if a log message is to be written. */ if (!log_checkpoints) return; TimestampDifference(CheckpointStats.ckpt_start_t, CheckpointStats.ckpt_end_t, &total_secs, &total_usecs); /* * Timing values returned from CheckpointStats are in microseconds. * Convert to the second plus microsecond form that TimestampDifference * returns for homogeneous printing. */ longest_secs = (long) (CheckpointStats.ckpt_longest_sync / 1000000); longest_usecs = CheckpointStats.ckpt_longest_sync - (uint64) longest_secs * 1000000; average_sync_time = 0; if (CheckpointStats.ckpt_sync_rels > 0) average_sync_time = CheckpointStats.ckpt_agg_sync_time / CheckpointStats.ckpt_sync_rels; average_secs = (long) (average_sync_time / 1000000); average_usecs = average_sync_time - (uint64) average_secs * 1000000; elog(LOG, "%s complete: wrote %d buffers (%.1f%%); " "%d WAL file(s) added, %d removed, %d recycled; " "write=%ld.%03d s, sync=%ld.%03d s, total=%ld.%03d s; " "sync files=%d, longest=%ld.%03d s, average=%ld.%03d s; " "distance=%d kB, estimate=%d kB", restartpoint ? "restartpoint" : "checkpoint", CheckpointStats.ckpt_bufs_written, (double) CheckpointStats.ckpt_bufs_written * 100 / NBuffers, CheckpointStats.ckpt_segs_added, CheckpointStats.ckpt_segs_removed, CheckpointStats.ckpt_segs_recycled, write_secs, write_usecs / 1000, sync_secs, sync_usecs / 1000, total_secs, total_usecs / 1000, CheckpointStats.ckpt_sync_rels, longest_secs, longest_usecs / 1000, average_secs, average_usecs / 1000, (int) (PrevCheckPointDistance / 1024.0), (int) (CheckPointDistanceEstimate / 1024.0)); } /* * Update the estimate of distance between checkpoints. * * The estimate is used to calculate the number of WAL segments to keep * preallocated, see XLOGfileslop(). */ static void UpdateCheckPointDistanceEstimate(uint64 nbytes) { /* * To estimate the number of segments consumed between checkpoints, keep a * moving average of the amount of WAL generated in previous checkpoint * cycles. However, if the load is bursty, with quiet periods and busy * periods, we want to cater for the peak load. So instead of a plain * moving average, let the average decline slowly if the previous cycle * used less WAL than estimated, but bump it up immediately if it used * more. * * When checkpoints are triggered by max_wal_size, this should converge to * CheckpointSegments * wal_segment_size, * * Note: This doesn't pay any attention to what caused the checkpoint. * Checkpoints triggered manually with CHECKPOINT command, or by e.g. * starting a base backup, are counted the same as those created * automatically. The slow-decline will largely mask them out, if they are * not frequent. If they are frequent, it seems reasonable to count them * in as any others; if you issue a manual checkpoint every 5 minutes and * never let a timed checkpoint happen, it makes sense to base the * preallocation on that 5 minute interval rather than whatever * checkpoint_timeout is set to. */ PrevCheckPointDistance = nbytes; if (CheckPointDistanceEstimate < nbytes) CheckPointDistanceEstimate = nbytes; else CheckPointDistanceEstimate = (0.90 * CheckPointDistanceEstimate + 0.10 * (double) nbytes); } /* * Perform a checkpoint --- either during shutdown, or on-the-fly * * flags is a bitwise OR of the following: * CHECKPOINT_IS_SHUTDOWN: checkpoint is for database shutdown. * CHECKPOINT_END_OF_RECOVERY: checkpoint is for end of WAL recovery. * CHECKPOINT_IMMEDIATE: finish the checkpoint ASAP, * ignoring checkpoint_completion_target parameter. * CHECKPOINT_FORCE: force a checkpoint even if no XLOG activity has occurred * since the last one (implied by CHECKPOINT_IS_SHUTDOWN or * CHECKPOINT_END_OF_RECOVERY). * CHECKPOINT_FLUSH_ALL: also flush buffers of unlogged tables. * * Note: flags contains other bits, of interest here only for logging purposes. * In particular note that this routine is synchronous and does not pay * attention to CHECKPOINT_WAIT. * * If !shutdown then we are writing an online checkpoint. This is a very special * kind of operation and WAL record because the checkpoint action occurs over * a period of time yet logically occurs at just a single LSN. The logical * position of the WAL record (redo ptr) is the same or earlier than the * physical position. When we replay WAL we locate the checkpoint via its * physical position then read the redo ptr and actually start replay at the * earlier logical position. Note that we don't write *anything* to WAL at * the logical position, so that location could be any other kind of WAL record. * All of this mechanism allows us to continue working while we checkpoint. * As a result, timing of actions is critical here and be careful to note that * this function will likely take minutes to execute on a busy system. */ void CreateCheckPoint(int flags) { bool shutdown; CheckPoint checkPoint; XLogRecPtr recptr; XLogSegNo _logSegNo; XLogCtlInsert *Insert = &XLogCtl->Insert; uint32 freespace; XLogRecPtr PriorRedoPtr; XLogRecPtr curInsert; XLogRecPtr last_important_lsn; VirtualTransactionId *vxids; int nvxids; /* * An end-of-recovery checkpoint is really a shutdown checkpoint, just * issued at a different time. */ if (flags & (CHECKPOINT_IS_SHUTDOWN | CHECKPOINT_END_OF_RECOVERY)) shutdown = true; else shutdown = false; /* sanity check */ if (RecoveryInProgress() && (flags & CHECKPOINT_END_OF_RECOVERY) == 0) elog(ERROR, "can't create a checkpoint during recovery"); /* * Initialize InitXLogInsert working areas before entering the critical * section. Normally, this is done by the first call to * RecoveryInProgress() or LocalSetXLogInsertAllowed(), but when creating * an end-of-recovery checkpoint, the LocalSetXLogInsertAllowed call is * done below in a critical section, and InitXLogInsert cannot be called * in a critical section. */ InitXLogInsert(); /* * Acquire CheckpointLock to ensure only one checkpoint happens at a time. * (This is just pro forma, since in the present system structure there is * only one process that is allowed to issue checkpoints at any given * time.) */ LWLockAcquire(CheckpointLock, LW_EXCLUSIVE); /* * Prepare to accumulate statistics. * * Note: because it is possible for log_checkpoints to change while a * checkpoint proceeds, we always accumulate stats, even if * log_checkpoints is currently off. */ MemSet(&CheckpointStats, 0, sizeof(CheckpointStats)); CheckpointStats.ckpt_start_t = GetCurrentTimestamp(); /* * Use a critical section to force system panic if we have trouble. */ START_CRIT_SECTION(); if (shutdown) { LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); ControlFile->state = DB_SHUTDOWNING; ControlFile->time = (pg_time_t) time(NULL); UpdateControlFile(); LWLockRelease(ControlFileLock); } /* * Let smgr prepare for checkpoint; this has to happen before we determine * the REDO pointer. Note that smgr must not do anything that'd have to * be undone if we decide no checkpoint is needed. */ SyncPreCheckpoint(); /* Begin filling in the checkpoint WAL record */ MemSet(&checkPoint, 0, sizeof(checkPoint)); checkPoint.time = (pg_time_t) time(NULL); /* * For Hot Standby, derive the oldestActiveXid before we fix the redo * pointer. This allows us to begin accumulating changes to assemble our * starting snapshot of locks and transactions. */ if (!shutdown && XLogStandbyInfoActive()) checkPoint.oldestActiveXid = GetOldestActiveTransactionId(); else checkPoint.oldestActiveXid = InvalidTransactionId; /* * Get location of last important record before acquiring insert locks (as * GetLastImportantRecPtr() also locks WAL locks). */ last_important_lsn = GetLastImportantRecPtr(); /* * We must block concurrent insertions while examining insert state to * determine the checkpoint REDO pointer. */ WALInsertLockAcquireExclusive(); curInsert = XLogBytePosToRecPtr(Insert->CurrBytePos); /* * If this isn't a shutdown or forced checkpoint, and if there has been no * WAL activity requiring a checkpoint, skip it. The idea here is to * avoid inserting duplicate checkpoints when the system is idle. */ if ((flags & (CHECKPOINT_IS_SHUTDOWN | CHECKPOINT_END_OF_RECOVERY | CHECKPOINT_FORCE)) == 0) { if (last_important_lsn == ControlFile->checkPoint) { WALInsertLockRelease(); LWLockRelease(CheckpointLock); END_CRIT_SECTION(); ereport(DEBUG1, (errmsg("checkpoint skipped because system is idle"))); return; } } /* * An end-of-recovery checkpoint is created before anyone is allowed to * write WAL. To allow us to write the checkpoint record, temporarily * enable XLogInsertAllowed. (This also ensures ThisTimeLineID is * initialized, which we need here and in AdvanceXLInsertBuffer.) */ if (flags & CHECKPOINT_END_OF_RECOVERY) LocalSetXLogInsertAllowed(); checkPoint.ThisTimeLineID = ThisTimeLineID; if (flags & CHECKPOINT_END_OF_RECOVERY) checkPoint.PrevTimeLineID = XLogCtl->PrevTimeLineID; else checkPoint.PrevTimeLineID = ThisTimeLineID; checkPoint.fullPageWrites = Insert->fullPageWrites; /* * Compute new REDO record ptr = location of next XLOG record. * * NB: this is NOT necessarily where the checkpoint record itself will be, * since other backends may insert more XLOG records while we're off doing * the buffer flush work. Those XLOG records are logically after the * checkpoint, even though physically before it. Got that? */ freespace = INSERT_FREESPACE(curInsert); if (freespace == 0) { if (XLogSegmentOffset(curInsert, wal_segment_size) == 0) curInsert += SizeOfXLogLongPHD; else curInsert += SizeOfXLogShortPHD; } checkPoint.redo = curInsert; /* * Here we update the shared RedoRecPtr for future XLogInsert calls; this * must be done while holding all the insertion locks. * * Note: if we fail to complete the checkpoint, RedoRecPtr will be left * pointing past where it really needs to point. This is okay; the only * consequence is that XLogInsert might back up whole buffers that it * didn't really need to. We can't postpone advancing RedoRecPtr because * XLogInserts that happen while we are dumping buffers must assume that * their buffer changes are not included in the checkpoint. */ RedoRecPtr = XLogCtl->Insert.RedoRecPtr = checkPoint.redo; /* * Now we can release the WAL insertion locks, allowing other xacts to * proceed while we are flushing disk buffers. */ WALInsertLockRelease(); /* Update the info_lck-protected copy of RedoRecPtr as well */ SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->RedoRecPtr = checkPoint.redo; SpinLockRelease(&XLogCtl->info_lck); /* * If enabled, log checkpoint start. We postpone this until now so as not * to log anything if we decided to skip the checkpoint. */ if (log_checkpoints) LogCheckpointStart(flags, false); TRACE_POSTGRESQL_CHECKPOINT_START(flags); /* * Get the other info we need for the checkpoint record. * * We don't need to save oldestClogXid in the checkpoint, it only matters * for the short period in which clog is being truncated, and if we crash * during that we'll redo the clog truncation and fix up oldestClogXid * there. */ LWLockAcquire(XidGenLock, LW_SHARED); checkPoint.nextFullXid = ShmemVariableCache->nextFullXid; checkPoint.oldestXid = ShmemVariableCache->oldestXid; checkPoint.oldestXidDB = ShmemVariableCache->oldestXidDB; LWLockRelease(XidGenLock); LWLockAcquire(CommitTsLock, LW_SHARED); checkPoint.oldestCommitTsXid = ShmemVariableCache->oldestCommitTsXid; checkPoint.newestCommitTsXid = ShmemVariableCache->newestCommitTsXid; LWLockRelease(CommitTsLock); LWLockAcquire(OidGenLock, LW_SHARED); checkPoint.nextOid = ShmemVariableCache->nextOid; if (!shutdown) checkPoint.nextOid += ShmemVariableCache->oidCount; LWLockRelease(OidGenLock); MultiXactGetCheckptMulti(shutdown, &checkPoint.nextMulti, &checkPoint.nextMultiOffset, &checkPoint.oldestMulti, &checkPoint.oldestMultiDB); /* * Having constructed the checkpoint record, ensure all shmem disk buffers * and commit-log buffers are flushed to disk. * * This I/O could fail for various reasons. If so, we will fail to * complete the checkpoint, but there is no reason to force a system * panic. Accordingly, exit critical section while doing it. */ END_CRIT_SECTION(); /* * In some cases there are groups of actions that must all occur on one * side or the other of a checkpoint record. Before flushing the * checkpoint record we must explicitly wait for any backend currently * performing those groups of actions. * * One example is end of transaction, so we must wait for any transactions * that are currently in commit critical sections. If an xact inserted * its commit record into XLOG just before the REDO point, then a crash * restart from the REDO point would not replay that record, which means * that our flushing had better include the xact's update of pg_xact. So * we wait till he's out of his commit critical section before proceeding. * See notes in RecordTransactionCommit(). * * Because we've already released the insertion locks, this test is a bit * fuzzy: it is possible that we will wait for xacts we didn't really need * to wait for. But the delay should be short and it seems better to make * checkpoint take a bit longer than to hold off insertions longer than * necessary. (In fact, the whole reason we have this issue is that xact.c * does commit record XLOG insertion and clog update as two separate steps * protected by different locks, but again that seems best on grounds of * minimizing lock contention.) * * A transaction that has not yet set delayChkpt when we look cannot be at * risk, since he's not inserted his commit record yet; and one that's * already cleared it is not at risk either, since he's done fixing clog * and we will correctly flush the update below. So we cannot miss any * xacts we need to wait for. */ vxids = GetVirtualXIDsDelayingChkpt(&nvxids); if (nvxids > 0) { do { pg_usleep(10000L); /* wait for 10 msec */ } while (HaveVirtualXIDsDelayingChkpt(vxids, nvxids)); } pfree(vxids); CheckPointGuts(checkPoint.redo, flags); /* * Take a snapshot of running transactions and write this to WAL. This * allows us to reconstruct the state of running transactions during * archive recovery, if required. Skip, if this info disabled. * * If we are shutting down, or Startup process is completing crash * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) LogStandbySnapshot(); START_CRIT_SECTION(); /* * Now insert the checkpoint record into XLOG. */ XLogBeginInsert(); XLogRegisterData((char *) (&checkPoint), sizeof(checkPoint)); recptr = XLogInsert(RM_XLOG_ID, shutdown ? XLOG_CHECKPOINT_SHUTDOWN : XLOG_CHECKPOINT_ONLINE); XLogFlush(recptr); /* * We mustn't write any new WAL after a shutdown checkpoint, or it will be * overwritten at next startup. No-one should even try, this just allows * sanity-checking. In the case of an end-of-recovery checkpoint, we want * to just temporarily disable writing until the system has exited * recovery. */ if (shutdown) { if (flags & CHECKPOINT_END_OF_RECOVERY) LocalXLogInsertAllowed = -1; /* return to "check" state */ else LocalXLogInsertAllowed = 0; /* never again write WAL */ } /* * We now have ProcLastRecPtr = start of actual checkpoint record, recptr * = end of actual checkpoint record. */ if (shutdown && checkPoint.redo != ProcLastRecPtr) ereport(PANIC, (errmsg("concurrent write-ahead log activity while database system is shutting down"))); /* * Remember the prior checkpoint's redo ptr for * UpdateCheckPointDistanceEstimate() */ PriorRedoPtr = ControlFile->checkPointCopy.redo; /* * Update the control file. */ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); if (shutdown) ControlFile->state = DB_SHUTDOWNED; ControlFile->checkPoint = ProcLastRecPtr; ControlFile->checkPointCopy = checkPoint; ControlFile->time = (pg_time_t) time(NULL); /* crash recovery should always recover to the end of WAL */ ControlFile->minRecoveryPoint = InvalidXLogRecPtr; ControlFile->minRecoveryPointTLI = 0; /* * Persist unloggedLSN value. It's reset on crash recovery, so this goes * unused on non-shutdown checkpoints, but seems useful to store it always * for debugging purposes. */ SpinLockAcquire(&XLogCtl->ulsn_lck); ControlFile->unloggedLSN = XLogCtl->unloggedLSN; SpinLockRelease(&XLogCtl->ulsn_lck); UpdateControlFile(); LWLockRelease(ControlFileLock); /* Update shared-memory copy of checkpoint XID/epoch */ SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->ckptFullXid = checkPoint.nextFullXid; SpinLockRelease(&XLogCtl->info_lck); /* * We are now done with critical updates; no need for system panic if we * have trouble while fooling with old log segments. */ END_CRIT_SECTION(); /* * Let smgr do post-checkpoint cleanup (eg, deleting old files). */ SyncPostCheckpoint(); /* * Update the average distance between checkpoints if the prior checkpoint * exists. */ if (PriorRedoPtr != InvalidXLogRecPtr) UpdateCheckPointDistanceEstimate(RedoRecPtr - PriorRedoPtr); /* * Delete old log files, those no longer needed for last checkpoint to * prevent the disk holding the xlog from growing full. */ XLByteToSeg(RedoRecPtr, _logSegNo, wal_segment_size); KeepLogSeg(recptr, &_logSegNo); _logSegNo--; RemoveOldXlogFiles(_logSegNo, RedoRecPtr, recptr); /* * Make more log segments if needed. (Do this after recycling old log * segments, since that may supply some of the needed files.) */ if (!shutdown) PreallocXlogFiles(recptr); /* * Truncate pg_subtrans if possible. We can throw away all data before * the oldest XMIN of any running transaction. No future transaction will * attempt to reference any pg_subtrans entry older than that (see Asserts * in subtrans.c). During recovery, though, we mustn't do this because * StartupSUBTRANS hasn't been called yet. */ if (!RecoveryInProgress()) TruncateSUBTRANS(GetOldestXmin(NULL, PROCARRAY_FLAGS_DEFAULT)); /* Real work is done, but log and update stats before releasing lock. */ LogCheckpointEnd(false); TRACE_POSTGRESQL_CHECKPOINT_DONE(CheckpointStats.ckpt_bufs_written, NBuffers, CheckpointStats.ckpt_segs_added, CheckpointStats.ckpt_segs_removed, CheckpointStats.ckpt_segs_recycled); LWLockRelease(CheckpointLock); } /* * Mark the end of recovery in WAL though without running a full checkpoint. * We can expect that a restartpoint is likely to be in progress as we * do this, though we are unwilling to wait for it to complete. So be * careful to avoid taking the CheckpointLock anywhere here. * * CreateRestartPoint() allows for the case where recovery may end before * the restartpoint completes so there is no concern of concurrent behaviour. */ static void CreateEndOfRecoveryRecord(void) { xl_end_of_recovery xlrec; XLogRecPtr recptr; /* sanity check */ if (!RecoveryInProgress()) elog(ERROR, "can only be used to end recovery"); xlrec.end_time = GetCurrentTimestamp(); WALInsertLockAcquireExclusive(); xlrec.ThisTimeLineID = ThisTimeLineID; xlrec.PrevTimeLineID = XLogCtl->PrevTimeLineID; WALInsertLockRelease(); LocalSetXLogInsertAllowed(); START_CRIT_SECTION(); XLogBeginInsert(); XLogRegisterData((char *) &xlrec, sizeof(xl_end_of_recovery)); recptr = XLogInsert(RM_XLOG_ID, XLOG_END_OF_RECOVERY); XLogFlush(recptr); /* * Update the control file so that crash recovery can follow the timeline * changes to this point. */ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); ControlFile->time = (pg_time_t) time(NULL); ControlFile->minRecoveryPoint = recptr; ControlFile->minRecoveryPointTLI = ThisTimeLineID; UpdateControlFile(); LWLockRelease(ControlFileLock); END_CRIT_SECTION(); LocalXLogInsertAllowed = -1; /* return to "check" state */ } /* * Flush all data in shared memory to disk, and fsync * * This is the common code shared between regular checkpoints and * recovery restartpoints. */ static void CheckPointGuts(XLogRecPtr checkPointRedo, int flags) { CheckPointCLOG(); CheckPointCommitTs(); CheckPointSUBTRANS(); CheckPointMultiXact(); CheckPointPredicate(); CheckPointRelationMap(); CheckPointReplicationSlots(); CheckPointSnapBuild(); CheckPointLogicalRewriteHeap(); CheckPointBuffers(flags); /* performs all required fsyncs */ CheckPointReplicationOrigin(); /* We deliberately delay 2PC checkpointing as long as possible */ CheckPointTwoPhase(checkPointRedo); } /* * Save a checkpoint for recovery restart if appropriate * * This function is called each time a checkpoint record is read from XLOG. * It must determine whether the checkpoint represents a safe restartpoint or * not. If so, the checkpoint record is stashed in shared memory so that * CreateRestartPoint can consult it. (Note that the latter function is * executed by the checkpointer, while this one will be executed by the * startup process.) */ static void RecoveryRestartPoint(const CheckPoint *checkPoint) { /* * Also refrain from creating a restartpoint if we have seen any * references to non-existent pages. Restarting recovery from the * restartpoint would not see the references, so we would lose the * cross-check that the pages belonged to a relation that was dropped * later. */ if (XLogHaveInvalidPages()) { elog(trace_recovery(DEBUG2), "could not record restart point at %X/%X because there " "are unresolved references to invalid pages", (uint32) (checkPoint->redo >> 32), (uint32) checkPoint->redo); return; } /* * Copy the checkpoint record to shared memory, so that checkpointer can * work out the next time it wants to perform a restartpoint. */ SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->lastCheckPointRecPtr = ReadRecPtr; XLogCtl->lastCheckPointEndPtr = EndRecPtr; XLogCtl->lastCheckPoint = *checkPoint; SpinLockRelease(&XLogCtl->info_lck); } /* * Establish a restartpoint if possible. * * This is similar to CreateCheckPoint, but is used during WAL recovery * to establish a point from which recovery can roll forward without * replaying the entire recovery log. * * Returns true if a new restartpoint was established. We can only establish * a restartpoint if we have replayed a safe checkpoint record since last * restartpoint. */ bool CreateRestartPoint(int flags) { XLogRecPtr lastCheckPointRecPtr; XLogRecPtr lastCheckPointEndPtr; CheckPoint lastCheckPoint; XLogRecPtr PriorRedoPtr; XLogRecPtr receivePtr; XLogRecPtr replayPtr; TimeLineID replayTLI; XLogRecPtr endptr; XLogSegNo _logSegNo; TimestampTz xtime; /* * Acquire CheckpointLock to ensure only one restartpoint or checkpoint * happens at a time. */ LWLockAcquire(CheckpointLock, LW_EXCLUSIVE); /* Get a local copy of the last safe checkpoint record. */ SpinLockAcquire(&XLogCtl->info_lck); lastCheckPointRecPtr = XLogCtl->lastCheckPointRecPtr; lastCheckPointEndPtr = XLogCtl->lastCheckPointEndPtr; lastCheckPoint = XLogCtl->lastCheckPoint; SpinLockRelease(&XLogCtl->info_lck); /* * Check that we're still in recovery mode. It's ok if we exit recovery * mode after this check, the restart point is valid anyway. */ if (!RecoveryInProgress()) { ereport(DEBUG2, (errmsg("skipping restartpoint, recovery has already ended"))); LWLockRelease(CheckpointLock); return false; } /* * If the last checkpoint record we've replayed is already our last * restartpoint, we can't perform a new restart point. We still update * minRecoveryPoint in that case, so that if this is a shutdown restart * point, we won't start up earlier than before. That's not strictly * necessary, but when hot standby is enabled, it would be rather weird if * the database opened up for read-only connections at a point-in-time * before the last shutdown. Such time travel is still possible in case of * immediate shutdown, though. * * We don't explicitly advance minRecoveryPoint when we do create a * restartpoint. It's assumed that flushing the buffers will do that as a * side-effect. */ if (XLogRecPtrIsInvalid(lastCheckPointRecPtr) || lastCheckPoint.redo <= ControlFile->checkPointCopy.redo) { ereport(DEBUG2, (errmsg("skipping restartpoint, already performed at %X/%X", (uint32) (lastCheckPoint.redo >> 32), (uint32) lastCheckPoint.redo))); UpdateMinRecoveryPoint(InvalidXLogRecPtr, true); if (flags & CHECKPOINT_IS_SHUTDOWN) { LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); ControlFile->state = DB_SHUTDOWNED_IN_RECOVERY; ControlFile->time = (pg_time_t) time(NULL); UpdateControlFile(); LWLockRelease(ControlFileLock); } LWLockRelease(CheckpointLock); return false; } /* * Update the shared RedoRecPtr so that the startup process can calculate * the number of segments replayed since last restartpoint, and request a * restartpoint if it exceeds CheckPointSegments. * * Like in CreateCheckPoint(), hold off insertions to update it, although * during recovery this is just pro forma, because no WAL insertions are * happening. */ WALInsertLockAcquireExclusive(); RedoRecPtr = XLogCtl->Insert.RedoRecPtr = lastCheckPoint.redo; WALInsertLockRelease(); /* Also update the info_lck-protected copy */ SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->RedoRecPtr = lastCheckPoint.redo; SpinLockRelease(&XLogCtl->info_lck); /* * Prepare to accumulate statistics. * * Note: because it is possible for log_checkpoints to change while a * checkpoint proceeds, we always accumulate stats, even if * log_checkpoints is currently off. */ MemSet(&CheckpointStats, 0, sizeof(CheckpointStats)); CheckpointStats.ckpt_start_t = GetCurrentTimestamp(); if (log_checkpoints) LogCheckpointStart(flags, true); CheckPointGuts(lastCheckPoint.redo, flags); /* * Remember the prior checkpoint's redo ptr for * UpdateCheckPointDistanceEstimate() */ PriorRedoPtr = ControlFile->checkPointCopy.redo; /* * Update pg_control, using current time. Check that it still shows * DB_IN_ARCHIVE_RECOVERY state and an older checkpoint, else do nothing; * this is a quick hack to make sure nothing really bad happens if somehow * we get here after the end-of-recovery checkpoint. */ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); if (ControlFile->state == DB_IN_ARCHIVE_RECOVERY && ControlFile->checkPointCopy.redo < lastCheckPoint.redo) { ControlFile->checkPoint = lastCheckPointRecPtr; ControlFile->checkPointCopy = lastCheckPoint; ControlFile->time = (pg_time_t) time(NULL); /* * Ensure minRecoveryPoint is past the checkpoint record. Normally, * this will have happened already while writing out dirty buffers, * but not necessarily - e.g. because no buffers were dirtied. We do * this because a non-exclusive base backup uses minRecoveryPoint to * determine which WAL files must be included in the backup, and the * file (or files) containing the checkpoint record must be included, * at a minimum. Note that for an ordinary restart of recovery there's * no value in having the minimum recovery point any earlier than this * anyway, because redo will begin just after the checkpoint record. */ if (ControlFile->minRecoveryPoint < lastCheckPointEndPtr) { ControlFile->minRecoveryPoint = lastCheckPointEndPtr; ControlFile->minRecoveryPointTLI = lastCheckPoint.ThisTimeLineID; /* update local copy */ minRecoveryPoint = ControlFile->minRecoveryPoint; minRecoveryPointTLI = ControlFile->minRecoveryPointTLI; } if (flags & CHECKPOINT_IS_SHUTDOWN) ControlFile->state = DB_SHUTDOWNED_IN_RECOVERY; UpdateControlFile(); } LWLockRelease(ControlFileLock); /* * Update the average distance between checkpoints/restartpoints if the * prior checkpoint exists. */ if (PriorRedoPtr != InvalidXLogRecPtr) UpdateCheckPointDistanceEstimate(RedoRecPtr - PriorRedoPtr); /* * Delete old log files, those no longer needed for last restartpoint to * prevent the disk holding the xlog from growing full. */ XLByteToSeg(RedoRecPtr, _logSegNo, wal_segment_size); /* * Retreat _logSegNo using the current end of xlog replayed or received, * whichever is later. */ receivePtr = GetWalRcvWriteRecPtr(NULL, NULL); replayPtr = GetXLogReplayRecPtr(&replayTLI); endptr = (receivePtr < replayPtr) ? replayPtr : receivePtr; KeepLogSeg(endptr, &_logSegNo); _logSegNo--; /* * Try to recycle segments on a useful timeline. If we've been promoted * since the beginning of this restartpoint, use the new timeline chosen * at end of recovery (RecoveryInProgress() sets ThisTimeLineID in that * case). If we're still in recovery, use the timeline we're currently * replaying. * * There is no guarantee that the WAL segments will be useful on the * current timeline; if recovery proceeds to a new timeline right after * this, the pre-allocated WAL segments on this timeline will not be used, * and will go wasted until recycled on the next restartpoint. We'll live * with that. */ if (RecoveryInProgress()) ThisTimeLineID = replayTLI; RemoveOldXlogFiles(_logSegNo, RedoRecPtr, endptr); /* * Make more log segments if needed. (Do this after recycling old log * segments, since that may supply some of the needed files.) */ PreallocXlogFiles(endptr); /* * ThisTimeLineID is normally not set when we're still in recovery. * However, recycling/preallocating segments above needed ThisTimeLineID * to determine which timeline to install the segments on. Reset it now, * to restore the normal state of affairs for debugging purposes. */ if (RecoveryInProgress()) ThisTimeLineID = 0; /* * Truncate pg_subtrans if possible. We can throw away all data before * the oldest XMIN of any running transaction. No future transaction will * attempt to reference any pg_subtrans entry older than that (see Asserts * in subtrans.c). When hot standby is disabled, though, we mustn't do * this because StartupSUBTRANS hasn't been called yet. */ if (EnableHotStandby) TruncateSUBTRANS(GetOldestXmin(NULL, PROCARRAY_FLAGS_DEFAULT)); /* Real work is done, but log and update before releasing lock. */ LogCheckpointEnd(true); xtime = GetLatestXTime(); ereport((log_checkpoints ? LOG : DEBUG2), (errmsg("recovery restart point at %X/%X", (uint32) (lastCheckPoint.redo >> 32), (uint32) lastCheckPoint.redo), xtime ? errdetail("Last completed transaction was at log time %s.", timestamptz_to_str(xtime)) : 0)); LWLockRelease(CheckpointLock); /* * Finally, execute archive_cleanup_command, if any. */ if (archiveCleanupCommand && strcmp(archiveCleanupCommand, "") != 0) ExecuteRecoveryCommand(archiveCleanupCommand, "archive_cleanup_command", false); return true; } /* * Retreat *logSegNo to the last segment that we need to retain because of * either wal_keep_segments or replication slots. * * This is calculated by subtracting wal_keep_segments from the given xlog * location, recptr and by making sure that that result is below the * requirement of replication slots. */ static void KeepLogSeg(XLogRecPtr recptr, XLogSegNo *logSegNo) { XLogSegNo segno; XLogRecPtr keep; XLByteToSeg(recptr, segno, wal_segment_size); keep = XLogGetReplicationSlotMinimumLSN(); /* compute limit for wal_keep_segments first */ if (wal_keep_segments > 0) { /* avoid underflow, don't go below 1 */ if (segno <= wal_keep_segments) segno = 1; else segno = segno - wal_keep_segments; } /* then check whether slots limit removal further */ if (max_replication_slots > 0 && keep != InvalidXLogRecPtr) { XLogSegNo slotSegNo; XLByteToSeg(keep, slotSegNo, wal_segment_size); if (slotSegNo <= 0) segno = 1; else if (slotSegNo < segno) segno = slotSegNo; } /* don't delete WAL segments newer than the calculated segment */ if (segno < *logSegNo) *logSegNo = segno; } /* * Write a NEXTOID log record */ void XLogPutNextOid(Oid nextOid) { XLogBeginInsert(); XLogRegisterData((char *) (&nextOid), sizeof(Oid)); (void) XLogInsert(RM_XLOG_ID, XLOG_NEXTOID); /* * We need not flush the NEXTOID record immediately, because any of the * just-allocated OIDs could only reach disk as part of a tuple insert or * update that would have its own XLOG record that must follow the NEXTOID * record. Therefore, the standard buffer LSN interlock applied to those * records will ensure no such OID reaches disk before the NEXTOID record * does. * * Note, however, that the above statement only covers state "within" the * database. When we use a generated OID as a file or directory name, we * are in a sense violating the basic WAL rule, because that filesystem * change may reach disk before the NEXTOID WAL record does. The impact * of this is that if a database crash occurs immediately afterward, we * might after restart re-generate the same OID and find that it conflicts * with the leftover file or directory. But since for safety's sake we * always loop until finding a nonconflicting filename, this poses no real * problem in practice. See pgsql-hackers discussion 27-Sep-2006. */ } /* * Write an XLOG SWITCH record. * * Here we just blindly issue an XLogInsert request for the record. * All the magic happens inside XLogInsert. * * The return value is either the end+1 address of the switch record, * or the end+1 address of the prior segment if we did not need to * write a switch record because we are already at segment start. */ XLogRecPtr RequestXLogSwitch(bool mark_unimportant) { XLogRecPtr RecPtr; /* XLOG SWITCH has no data */ XLogBeginInsert(); if (mark_unimportant) XLogSetRecordFlags(XLOG_MARK_UNIMPORTANT); RecPtr = XLogInsert(RM_XLOG_ID, XLOG_SWITCH); return RecPtr; } /* * Write a RESTORE POINT record */ XLogRecPtr XLogRestorePoint(const char *rpName) { XLogRecPtr RecPtr; xl_restore_point xlrec; xlrec.rp_time = GetCurrentTimestamp(); strlcpy(xlrec.rp_name, rpName, MAXFNAMELEN); XLogBeginInsert(); XLogRegisterData((char *) &xlrec, sizeof(xl_restore_point)); RecPtr = XLogInsert(RM_XLOG_ID, XLOG_RESTORE_POINT); ereport(LOG, (errmsg("restore point \"%s\" created at %X/%X", rpName, (uint32) (RecPtr >> 32), (uint32) RecPtr))); return RecPtr; } /* * Check if any of the GUC parameters that are critical for hot standby * have changed, and update the value in pg_control file if necessary. */ static void XLogReportParameters(void) { if (wal_level != ControlFile->wal_level || wal_log_hints != ControlFile->wal_log_hints || MaxConnections != ControlFile->MaxConnections || max_worker_processes != ControlFile->max_worker_processes || max_wal_senders != ControlFile->max_wal_senders || max_prepared_xacts != ControlFile->max_prepared_xacts || max_locks_per_xact != ControlFile->max_locks_per_xact || track_commit_timestamp != ControlFile->track_commit_timestamp) { /* * The change in number of backend slots doesn't need to be WAL-logged * if archiving is not enabled, as you can't start archive recovery * with wal_level=minimal anyway. We don't really care about the * values in pg_control either if wal_level=minimal, but seems better * to keep them up-to-date to avoid confusion. */ if (wal_level != ControlFile->wal_level || XLogIsNeeded()) { xl_parameter_change xlrec; XLogRecPtr recptr; xlrec.MaxConnections = MaxConnections; xlrec.max_worker_processes = max_worker_processes; xlrec.max_wal_senders = max_wal_senders; xlrec.max_prepared_xacts = max_prepared_xacts; xlrec.max_locks_per_xact = max_locks_per_xact; xlrec.wal_level = wal_level; xlrec.wal_log_hints = wal_log_hints; xlrec.track_commit_timestamp = track_commit_timestamp; XLogBeginInsert(); XLogRegisterData((char *) &xlrec, sizeof(xlrec)); recptr = XLogInsert(RM_XLOG_ID, XLOG_PARAMETER_CHANGE); XLogFlush(recptr); } ControlFile->MaxConnections = MaxConnections; ControlFile->max_worker_processes = max_worker_processes; ControlFile->max_wal_senders = max_wal_senders; ControlFile->max_prepared_xacts = max_prepared_xacts; ControlFile->max_locks_per_xact = max_locks_per_xact; ControlFile->wal_level = wal_level; ControlFile->wal_log_hints = wal_log_hints; ControlFile->track_commit_timestamp = track_commit_timestamp; UpdateControlFile(); } } /* * Update full_page_writes in shared memory, and write an * XLOG_FPW_CHANGE record if necessary. * * Note: this function assumes there is no other process running * concurrently that could update it. */ void UpdateFullPageWrites(void) { XLogCtlInsert *Insert = &XLogCtl->Insert; bool recoveryInProgress; /* * Do nothing if full_page_writes has not been changed. * * It's safe to check the shared full_page_writes without the lock, * because we assume that there is no concurrently running process which * can update it. */ if (fullPageWrites == Insert->fullPageWrites) return; /* * Perform this outside critical section so that the WAL insert * initialization done by RecoveryInProgress() doesn't trigger an * assertion failure. */ recoveryInProgress = RecoveryInProgress(); START_CRIT_SECTION(); /* * It's always safe to take full page images, even when not strictly * required, but not the other round. So if we're setting full_page_writes * to true, first set it true and then write the WAL record. If we're * setting it to false, first write the WAL record and then set the global * flag. */ if (fullPageWrites) { WALInsertLockAcquireExclusive(); Insert->fullPageWrites = true; WALInsertLockRelease(); } /* * Write an XLOG_FPW_CHANGE record. This allows us to keep track of * full_page_writes during archive recovery, if required. */ if (XLogStandbyInfoActive() && !recoveryInProgress) { XLogBeginInsert(); XLogRegisterData((char *) (&fullPageWrites), sizeof(bool)); XLogInsert(RM_XLOG_ID, XLOG_FPW_CHANGE); } if (!fullPageWrites) { WALInsertLockAcquireExclusive(); Insert->fullPageWrites = false; WALInsertLockRelease(); } END_CRIT_SECTION(); } /* * Check that it's OK to switch to new timeline during recovery. * * 'lsn' is the address of the shutdown checkpoint record we're about to * replay. (Currently, timeline can only change at a shutdown checkpoint). */ static void checkTimeLineSwitch(XLogRecPtr lsn, TimeLineID newTLI, TimeLineID prevTLI) { /* Check that the record agrees on what the current (old) timeline is */ if (prevTLI != ThisTimeLineID) ereport(PANIC, (errmsg("unexpected previous timeline ID %u (current timeline ID %u) in checkpoint record", prevTLI, ThisTimeLineID))); /* * The new timeline better be in the list of timelines we expect to see, * according to the timeline history. It should also not decrease. */ if (newTLI < ThisTimeLineID || !tliInHistory(newTLI, expectedTLEs)) ereport(PANIC, (errmsg("unexpected timeline ID %u (after %u) in checkpoint record", newTLI, ThisTimeLineID))); /* * If we have not yet reached min recovery point, and we're about to * switch to a timeline greater than the timeline of the min recovery * point: trouble. After switching to the new timeline, we could not * possibly visit the min recovery point on the correct timeline anymore. * This can happen if there is a newer timeline in the archive that * branched before the timeline the min recovery point is on, and you * attempt to do PITR to the new timeline. */ if (!XLogRecPtrIsInvalid(minRecoveryPoint) && lsn < minRecoveryPoint && newTLI > minRecoveryPointTLI) ereport(PANIC, (errmsg("unexpected timeline ID %u in checkpoint record, before reaching minimum recovery point %X/%X on timeline %u", newTLI, (uint32) (minRecoveryPoint >> 32), (uint32) minRecoveryPoint, minRecoveryPointTLI))); /* Looks good */ } /* * XLOG resource manager's routines * * Definitions of info values are in include/catalog/pg_control.h, though * not all record types are related to control file updates. */ void xlog_redo(XLogReaderState *record) { uint8 info = XLogRecGetInfo(record) & ~XLR_INFO_MASK; XLogRecPtr lsn = record->EndRecPtr; /* in XLOG rmgr, backup blocks are only used by XLOG_FPI records */ Assert(info == XLOG_FPI || info == XLOG_FPI_FOR_HINT || !XLogRecHasAnyBlockRefs(record)); if (info == XLOG_NEXTOID) { Oid nextOid; /* * We used to try to take the maximum of ShmemVariableCache->nextOid * and the recorded nextOid, but that fails if the OID counter wraps * around. Since no OID allocation should be happening during replay * anyway, better to just believe the record exactly. We still take * OidGenLock while setting the variable, just in case. */ memcpy(&nextOid, XLogRecGetData(record), sizeof(Oid)); LWLockAcquire(OidGenLock, LW_EXCLUSIVE); ShmemVariableCache->nextOid = nextOid; ShmemVariableCache->oidCount = 0; LWLockRelease(OidGenLock); } else if (info == XLOG_CHECKPOINT_SHUTDOWN) { CheckPoint checkPoint; memcpy(&checkPoint, XLogRecGetData(record), sizeof(CheckPoint)); /* In a SHUTDOWN checkpoint, believe the counters exactly */ LWLockAcquire(XidGenLock, LW_EXCLUSIVE); ShmemVariableCache->nextFullXid = checkPoint.nextFullXid; LWLockRelease(XidGenLock); LWLockAcquire(OidGenLock, LW_EXCLUSIVE); ShmemVariableCache->nextOid = checkPoint.nextOid; ShmemVariableCache->oidCount = 0; LWLockRelease(OidGenLock); MultiXactSetNextMXact(checkPoint.nextMulti, checkPoint.nextMultiOffset); MultiXactAdvanceOldest(checkPoint.oldestMulti, checkPoint.oldestMultiDB); /* * No need to set oldestClogXid here as well; it'll be set when we * redo an xl_clog_truncate if it changed since initialization. */ SetTransactionIdLimit(checkPoint.oldestXid, checkPoint.oldestXidDB); /* * If we see a shutdown checkpoint while waiting for an end-of-backup * record, the backup was canceled and the end-of-backup record will * never arrive. */ if (ArchiveRecoveryRequested && !XLogRecPtrIsInvalid(ControlFile->backupStartPoint) && XLogRecPtrIsInvalid(ControlFile->backupEndPoint)) ereport(PANIC, (errmsg("online backup was canceled, recovery cannot continue"))); /* * If we see a shutdown checkpoint, we know that nothing was running * on the master at this point. So fake-up an empty running-xacts * record and use that here and now. Recover additional standby state * for prepared transactions. */ if (standbyState >= STANDBY_INITIALIZED) { TransactionId *xids; int nxids; TransactionId oldestActiveXID; TransactionId latestCompletedXid; RunningTransactionsData running; oldestActiveXID = PrescanPreparedTransactions(&xids, &nxids); /* * Construct a RunningTransactions snapshot representing a shut * down server, with only prepared transactions still alive. We're * never overflowed at this point because all subxids are listed * with their parent prepared transactions. */ running.xcnt = nxids; running.subxcnt = 0; running.subxid_overflow = false; running.nextXid = XidFromFullTransactionId(checkPoint.nextFullXid); running.oldestRunningXid = oldestActiveXID; latestCompletedXid = XidFromFullTransactionId(checkPoint.nextFullXid); TransactionIdRetreat(latestCompletedXid); Assert(TransactionIdIsNormal(latestCompletedXid)); running.latestCompletedXid = latestCompletedXid; running.xids = xids; ProcArrayApplyRecoveryInfo(&running); StandbyRecoverPreparedTransactions(); } /* ControlFile->checkPointCopy always tracks the latest ckpt XID */ ControlFile->checkPointCopy.nextFullXid = checkPoint.nextFullXid; /* Update shared-memory copy of checkpoint XID/epoch */ SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->ckptFullXid = checkPoint.nextFullXid; SpinLockRelease(&XLogCtl->info_lck); /* * We should've already switched to the new TLI before replaying this * record. */ if (checkPoint.ThisTimeLineID != ThisTimeLineID) ereport(PANIC, (errmsg("unexpected timeline ID %u (should be %u) in checkpoint record", checkPoint.ThisTimeLineID, ThisTimeLineID))); RecoveryRestartPoint(&checkPoint); } else if (info == XLOG_CHECKPOINT_ONLINE) { CheckPoint checkPoint; memcpy(&checkPoint, XLogRecGetData(record), sizeof(CheckPoint)); /* In an ONLINE checkpoint, treat the XID counter as a minimum */ LWLockAcquire(XidGenLock, LW_EXCLUSIVE); if (FullTransactionIdPrecedes(ShmemVariableCache->nextFullXid, checkPoint.nextFullXid)) ShmemVariableCache->nextFullXid = checkPoint.nextFullXid; LWLockRelease(XidGenLock); /* * We ignore the nextOid counter in an ONLINE checkpoint, preferring * to track OID assignment through XLOG_NEXTOID records. The nextOid * counter is from the start of the checkpoint and might well be stale * compared to later XLOG_NEXTOID records. We could try to take the * maximum of the nextOid counter and our latest value, but since * there's no particular guarantee about the speed with which the OID * counter wraps around, that's a risky thing to do. In any case, * users of the nextOid counter are required to avoid assignment of * duplicates, so that a somewhat out-of-date value should be safe. */ /* Handle multixact */ MultiXactAdvanceNextMXact(checkPoint.nextMulti, checkPoint.nextMultiOffset); /* * NB: This may perform multixact truncation when replaying WAL * generated by an older primary. */ MultiXactAdvanceOldest(checkPoint.oldestMulti, checkPoint.oldestMultiDB); if (TransactionIdPrecedes(ShmemVariableCache->oldestXid, checkPoint.oldestXid)) SetTransactionIdLimit(checkPoint.oldestXid, checkPoint.oldestXidDB); /* ControlFile->checkPointCopy always tracks the latest ckpt XID */ ControlFile->checkPointCopy.nextFullXid = checkPoint.nextFullXid; /* Update shared-memory copy of checkpoint XID/epoch */ SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->ckptFullXid = checkPoint.nextFullXid; SpinLockRelease(&XLogCtl->info_lck); /* TLI should not change in an on-line checkpoint */ if (checkPoint.ThisTimeLineID != ThisTimeLineID) ereport(PANIC, (errmsg("unexpected timeline ID %u (should be %u) in checkpoint record", checkPoint.ThisTimeLineID, ThisTimeLineID))); RecoveryRestartPoint(&checkPoint); } else if (info == XLOG_END_OF_RECOVERY) { xl_end_of_recovery xlrec; memcpy(&xlrec, XLogRecGetData(record), sizeof(xl_end_of_recovery)); /* * For Hot Standby, we could treat this like a Shutdown Checkpoint, * but this case is rarer and harder to test, so the benefit doesn't * outweigh the potential extra cost of maintenance. */ /* * We should've already switched to the new TLI before replaying this * record. */ if (xlrec.ThisTimeLineID != ThisTimeLineID) ereport(PANIC, (errmsg("unexpected timeline ID %u (should be %u) in checkpoint record", xlrec.ThisTimeLineID, ThisTimeLineID))); } else if (info == XLOG_NOOP) { /* nothing to do here */ } else if (info == XLOG_SWITCH) { /* nothing to do here */ } else if (info == XLOG_RESTORE_POINT) { /* nothing to do here */ } else if (info == XLOG_FPI || info == XLOG_FPI_FOR_HINT) { /* * Full-page image (FPI) records contain nothing else but a backup * block (or multiple backup blocks). Every block reference must * include a full-page image - otherwise there would be no point in * this record. * * No recovery conflicts are generated by these generic records - if a * resource manager needs to generate conflicts, it has to define a * separate WAL record type and redo routine. * * XLOG_FPI_FOR_HINT records are generated when a page needs to be * WAL- logged because of a hint bit update. They are only generated * when checksums are enabled. There is no difference in handling * XLOG_FPI and XLOG_FPI_FOR_HINT records, they use a different info * code just to distinguish them for statistics purposes. */ for (uint8 block_id = 0; block_id <= record->max_block_id; block_id++) { Buffer buffer; if (XLogReadBufferForRedo(record, block_id, &buffer) != BLK_RESTORED) elog(ERROR, "unexpected XLogReadBufferForRedo result when restoring backup block"); UnlockReleaseBuffer(buffer); } } else if (info == XLOG_BACKUP_END) { XLogRecPtr startpoint; memcpy(&startpoint, XLogRecGetData(record), sizeof(startpoint)); if (ControlFile->backupStartPoint == startpoint) { /* * We have reached the end of base backup, the point where * pg_stop_backup() was done. The data on disk is now consistent. * Reset backupStartPoint, and update minRecoveryPoint to make * sure we don't allow starting up at an earlier point even if * recovery is stopped and restarted soon after this. */ elog(DEBUG1, "end of backup reached"); LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); if (ControlFile->minRecoveryPoint < lsn) { ControlFile->minRecoveryPoint = lsn; ControlFile->minRecoveryPointTLI = ThisTimeLineID; } ControlFile->backupStartPoint = InvalidXLogRecPtr; ControlFile->backupEndRequired = false; UpdateControlFile(); LWLockRelease(ControlFileLock); } } else if (info == XLOG_PARAMETER_CHANGE) { xl_parameter_change xlrec; /* Update our copy of the parameters in pg_control */ memcpy(&xlrec, XLogRecGetData(record), sizeof(xl_parameter_change)); LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); ControlFile->MaxConnections = xlrec.MaxConnections; ControlFile->max_worker_processes = xlrec.max_worker_processes; ControlFile->max_wal_senders = xlrec.max_wal_senders; ControlFile->max_prepared_xacts = xlrec.max_prepared_xacts; ControlFile->max_locks_per_xact = xlrec.max_locks_per_xact; ControlFile->wal_level = xlrec.wal_level; ControlFile->wal_log_hints = xlrec.wal_log_hints; /* * Update minRecoveryPoint to ensure that if recovery is aborted, we * recover back up to this point before allowing hot standby again. * This is important if the max_* settings are decreased, to ensure * you don't run queries against the WAL preceding the change. The * local copies cannot be updated as long as crash recovery is * happening and we expect all the WAL to be replayed. */ if (InArchiveRecovery) { minRecoveryPoint = ControlFile->minRecoveryPoint; minRecoveryPointTLI = ControlFile->minRecoveryPointTLI; } if (minRecoveryPoint != InvalidXLogRecPtr && minRecoveryPoint < lsn) { ControlFile->minRecoveryPoint = lsn; ControlFile->minRecoveryPointTLI = ThisTimeLineID; } CommitTsParameterChange(xlrec.track_commit_timestamp, ControlFile->track_commit_timestamp); ControlFile->track_commit_timestamp = xlrec.track_commit_timestamp; UpdateControlFile(); LWLockRelease(ControlFileLock); /* Check to see if any parameter change gives a problem on recovery */ CheckRequiredParameterValues(); } else if (info == XLOG_FPW_CHANGE) { bool fpw; memcpy(&fpw, XLogRecGetData(record), sizeof(bool)); /* * Update the LSN of the last replayed XLOG_FPW_CHANGE record so that * do_pg_start_backup() and do_pg_stop_backup() can check whether * full_page_writes has been disabled during online backup. */ if (!fpw) { SpinLockAcquire(&XLogCtl->info_lck); if (XLogCtl->lastFpwDisableRecPtr < ReadRecPtr) XLogCtl->lastFpwDisableRecPtr = ReadRecPtr; SpinLockRelease(&XLogCtl->info_lck); } /* Keep track of full_page_writes */ lastFullPageWrites = fpw; } } #ifdef WAL_DEBUG static void xlog_outrec(StringInfo buf, XLogReaderState *record) { int block_id; appendStringInfo(buf, "prev %X/%X; xid %u", (uint32) (XLogRecGetPrev(record) >> 32), (uint32) XLogRecGetPrev(record), XLogRecGetXid(record)); appendStringInfo(buf, "; len %u", XLogRecGetDataLen(record)); /* decode block references */ for (block_id = 0; block_id <= record->max_block_id; block_id++) { RelFileNode rnode; ForkNumber forknum; BlockNumber blk; if (!XLogRecHasBlockRef(record, block_id)) continue; XLogRecGetBlockTag(record, block_id, &rnode, &forknum, &blk); if (forknum != MAIN_FORKNUM) appendStringInfo(buf, "; blkref #%u: rel %u/%u/%u, fork %u, blk %u", block_id, rnode.spcNode, rnode.dbNode, rnode.relNode, forknum, blk); else appendStringInfo(buf, "; blkref #%u: rel %u/%u/%u, blk %u", block_id, rnode.spcNode, rnode.dbNode, rnode.relNode, blk); if (XLogRecHasBlockImage(record, block_id)) appendStringInfoString(buf, " FPW"); } } #endif /* WAL_DEBUG */ /* * Returns a string describing an XLogRecord, consisting of its identity * optionally followed by a colon, a space, and a further description. */ static void xlog_outdesc(StringInfo buf, XLogReaderState *record) { RmgrId rmid = XLogRecGetRmid(record); uint8 info = XLogRecGetInfo(record); const char *id; appendStringInfoString(buf, RmgrTable[rmid].rm_name); appendStringInfoChar(buf, '/'); id = RmgrTable[rmid].rm_identify(info); if (id == NULL) appendStringInfo(buf, "UNKNOWN (%X): ", info & ~XLR_INFO_MASK); else appendStringInfo(buf, "%s: ", id); RmgrTable[rmid].rm_desc(buf, record); } /* * Return the (possible) sync flag used for opening a file, depending on the * value of the GUC wal_sync_method. */ static int get_sync_bit(int method) { int o_direct_flag = 0; /* If fsync is disabled, never open in sync mode */ if (!enableFsync) return 0; /* * Optimize writes by bypassing kernel cache with O_DIRECT when using * O_SYNC/O_FSYNC and O_DSYNC. But only if archiving and streaming are * disabled, otherwise the archive command or walsender process will read * the WAL soon after writing it, which is guaranteed to cause a physical * read if we bypassed the kernel cache. We also skip the * posix_fadvise(POSIX_FADV_DONTNEED) call in XLogFileClose() for the same * reason. * * Never use O_DIRECT in walreceiver process for similar reasons; the WAL * written by walreceiver is normally read by the startup process soon * after its written. Also, walreceiver performs unaligned writes, which * don't work with O_DIRECT, so it is required for correctness too. */ if (!XLogIsNeeded() && !AmWalReceiverProcess()) o_direct_flag = PG_O_DIRECT; switch (method) { /* * enum values for all sync options are defined even if they are * not supported on the current platform. But if not, they are * not included in the enum option array, and therefore will never * be seen here. */ case SYNC_METHOD_FSYNC: case SYNC_METHOD_FSYNC_WRITETHROUGH: case SYNC_METHOD_FDATASYNC: return 0; #ifdef OPEN_SYNC_FLAG case SYNC_METHOD_OPEN: return OPEN_SYNC_FLAG | o_direct_flag; #endif #ifdef OPEN_DATASYNC_FLAG case SYNC_METHOD_OPEN_DSYNC: return OPEN_DATASYNC_FLAG | o_direct_flag; #endif default: /* can't happen (unless we are out of sync with option array) */ elog(ERROR, "unrecognized wal_sync_method: %d", method); return 0; /* silence warning */ } } /* * GUC support */ void assign_xlog_sync_method(int new_sync_method, void *extra) { if (sync_method != new_sync_method) { /* * To ensure that no blocks escape unsynced, force an fsync on the * currently open log segment (if any). Also, if the open flag is * changing, close the log file so it will be reopened (with new flag * bit) at next use. */ if (openLogFile >= 0) { pgstat_report_wait_start(WAIT_EVENT_WAL_SYNC_METHOD_ASSIGN); if (pg_fsync(openLogFile) != 0) { char xlogfname[MAXFNAMELEN]; int save_errno; save_errno = errno; XLogFileName(xlogfname, ThisTimeLineID, openLogSegNo, wal_segment_size); errno = save_errno; ereport(PANIC, (errcode_for_file_access(), errmsg("could not fsync file \"%s\": %m", xlogfname))); } pgstat_report_wait_end(); if (get_sync_bit(sync_method) != get_sync_bit(new_sync_method)) XLogFileClose(); } } } /* * Issue appropriate kind of fsync (if any) for an XLOG output file. * * 'fd' is a file descriptor for the XLOG file to be fsync'd. * 'segno' is for error reporting purposes. */ void issue_xlog_fsync(int fd, XLogSegNo segno) { char *msg = NULL; pgstat_report_wait_start(WAIT_EVENT_WAL_SYNC); switch (sync_method) { case SYNC_METHOD_FSYNC: if (pg_fsync_no_writethrough(fd) != 0) msg = _("could not fsync file \"%s\": %m"); break; #ifdef HAVE_FSYNC_WRITETHROUGH case SYNC_METHOD_FSYNC_WRITETHROUGH: if (pg_fsync_writethrough(fd) != 0) msg = _("could not fsync write-through file \"%s\": %m"); break; #endif #ifdef HAVE_FDATASYNC case SYNC_METHOD_FDATASYNC: if (pg_fdatasync(fd) != 0) msg = _("could not fdatasync file \"%s\": %m"); break; #endif case SYNC_METHOD_OPEN: case SYNC_METHOD_OPEN_DSYNC: /* write synced it already */ break; default: elog(PANIC, "unrecognized wal_sync_method: %d", sync_method); break; } /* PANIC if failed to fsync */ if (msg) { char xlogfname[MAXFNAMELEN]; int save_errno = errno; XLogFileName(xlogfname, ThisTimeLineID, segno, wal_segment_size); errno = save_errno; ereport(PANIC, (errcode_for_file_access(), errmsg(msg, xlogfname))); } pgstat_report_wait_end(); } /* * do_pg_start_backup * * Utility function called at the start of an online backup. It creates the * necessary starting checkpoint and constructs the backup label file. * * There are two kind of backups: exclusive and non-exclusive. An exclusive * backup is started with pg_start_backup(), and there can be only one active * at a time. The backup and tablespace map files of an exclusive backup are * written to $PGDATA/backup_label and $PGDATA/tablespace_map, and they are * removed by pg_stop_backup(). * * A non-exclusive backup is used for the streaming base backups (see * src/backend/replication/basebackup.c). The difference to exclusive backups * is that the backup label and tablespace map files are not written to disk. * Instead, their would-be contents are returned in *labelfile and *tblspcmapfile, * and the caller is responsible for including them in the backup archive as * 'backup_label' and 'tablespace_map'. There can be many non-exclusive backups * active at the same time, and they don't conflict with an exclusive backup * either. * * tblspcmapfile is required mainly for tar format in windows as native windows * utilities are not able to create symlinks while extracting files from tar. * However for consistency, the same is used for all platforms. * * needtblspcmapfile is true for the cases (exclusive backup and for * non-exclusive backup only when tar format is used for taking backup) * when backup needs to generate tablespace_map file, it is used to * embed escape character before newline character in tablespace path. * * Returns the minimum WAL location that must be present to restore from this * backup, and the corresponding timeline ID in *starttli_p. * * Every successfully started non-exclusive backup must be stopped by calling * do_pg_stop_backup() or do_pg_abort_backup(). * * It is the responsibility of the caller of this function to verify the * permissions of the calling user! */ XLogRecPtr do_pg_start_backup(const char *backupidstr, bool fast, TimeLineID *starttli_p, StringInfo labelfile, List **tablespaces, StringInfo tblspcmapfile, bool infotbssize, bool needtblspcmapfile) { bool exclusive = (labelfile == NULL); bool backup_started_in_recovery = false; XLogRecPtr checkpointloc; XLogRecPtr startpoint; TimeLineID starttli; pg_time_t stamp_time; char strfbuf[128]; char xlogfilename[MAXFNAMELEN]; XLogSegNo _logSegNo; struct stat stat_buf; FILE *fp; backup_started_in_recovery = RecoveryInProgress(); /* * Currently only non-exclusive backup can be taken during recovery. */ if (backup_started_in_recovery && exclusive) ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("recovery is in progress"), errhint("WAL control functions cannot be executed during recovery."))); /* * During recovery, we don't need to check WAL level. Because, if WAL * level is not sufficient, it's impossible to get here during recovery. */ if (!backup_started_in_recovery && !XLogIsNeeded()) ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("WAL level not sufficient for making an online backup"), errhint("wal_level must be set to \"replica\" or \"logical\" at server start."))); if (strlen(backupidstr) > MAXPGPATH) ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE), errmsg("backup label too long (max %d bytes)", MAXPGPATH))); /* * Mark backup active in shared memory. We must do full-page WAL writes * during an on-line backup even if not doing so at other times, because * it's quite possible for the backup dump to obtain a "torn" (partially * written) copy of a database page if it reads the page concurrently with * our write to the same page. This can be fixed as long as the first * write to the page in the WAL sequence is a full-page write. Hence, we * turn on forcePageWrites and then force a CHECKPOINT, to ensure there * are no dirty pages in shared memory that might get dumped while the * backup is in progress without having a corresponding WAL record. (Once * the backup is complete, we need not force full-page writes anymore, * since we expect that any pages not modified during the backup interval * must have been correctly captured by the backup.) * * Note that forcePageWrites has no effect during an online backup from * the standby. * * We must hold all the insertion locks to change the value of * forcePageWrites, to ensure adequate interlocking against * XLogInsertRecord(). */ WALInsertLockAcquireExclusive(); if (exclusive) { /* * At first, mark that we're now starting an exclusive backup, to * ensure that there are no other sessions currently running * pg_start_backup() or pg_stop_backup(). */ if (XLogCtl->Insert.exclusiveBackupState != EXCLUSIVE_BACKUP_NONE) { WALInsertLockRelease(); ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("a backup is already in progress"), errhint("Run pg_stop_backup() and try again."))); } XLogCtl->Insert.exclusiveBackupState = EXCLUSIVE_BACKUP_STARTING; } else XLogCtl->Insert.nonExclusiveBackups++; XLogCtl->Insert.forcePageWrites = true; WALInsertLockRelease(); /* Ensure we release forcePageWrites if fail below */ PG_ENSURE_ERROR_CLEANUP(pg_start_backup_callback, (Datum) BoolGetDatum(exclusive)); { bool gotUniqueStartpoint = false; DIR *tblspcdir; struct dirent *de; tablespaceinfo *ti; int datadirpathlen; /* * Force an XLOG file switch before the checkpoint, to ensure that the * WAL segment the checkpoint is written to doesn't contain pages with * old timeline IDs. That would otherwise happen if you called * pg_start_backup() right after restoring from a PITR archive: the * first WAL segment containing the startup checkpoint has pages in * the beginning with the old timeline ID. That can cause trouble at * recovery: we won't have a history file covering the old timeline if * pg_wal directory was not included in the base backup and the WAL * archive was cleared too before starting the backup. * * This also ensures that we have emitted a WAL page header that has * XLP_BKP_REMOVABLE off before we emit the checkpoint record. * Therefore, if a WAL archiver (such as pglesslog) is trying to * compress out removable backup blocks, it won't remove any that * occur after this point. * * During recovery, we skip forcing XLOG file switch, which means that * the backup taken during recovery is not available for the special * recovery case described above. */ if (!backup_started_in_recovery) RequestXLogSwitch(false); do { bool checkpointfpw; /* * Force a CHECKPOINT. Aside from being necessary to prevent torn * page problems, this guarantees that two successive backup runs * will have different checkpoint positions and hence different * history file names, even if nothing happened in between. * * During recovery, establish a restartpoint if possible. We use * the last restartpoint as the backup starting checkpoint. This * means that two successive backup runs can have same checkpoint * positions. * * Since the fact that we are executing do_pg_start_backup() * during recovery means that checkpointer is running, we can use * RequestCheckpoint() to establish a restartpoint. * * We use CHECKPOINT_IMMEDIATE only if requested by user (via * passing fast = true). Otherwise this can take awhile. */ RequestCheckpoint(CHECKPOINT_FORCE | CHECKPOINT_WAIT | (fast ? CHECKPOINT_IMMEDIATE : 0)); /* * Now we need to fetch the checkpoint record location, and also * its REDO pointer. The oldest point in WAL that would be needed * to restore starting from the checkpoint is precisely the REDO * pointer. */ LWLockAcquire(ControlFileLock, LW_SHARED); checkpointloc = ControlFile->checkPoint; startpoint = ControlFile->checkPointCopy.redo; starttli = ControlFile->checkPointCopy.ThisTimeLineID; checkpointfpw = ControlFile->checkPointCopy.fullPageWrites; LWLockRelease(ControlFileLock); if (backup_started_in_recovery) { XLogRecPtr recptr; /* * Check to see if all WAL replayed during online backup * (i.e., since last restartpoint used as backup starting * checkpoint) contain full-page writes. */ SpinLockAcquire(&XLogCtl->info_lck); recptr = XLogCtl->lastFpwDisableRecPtr; SpinLockRelease(&XLogCtl->info_lck); if (!checkpointfpw || startpoint <= recptr) ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("WAL generated with full_page_writes=off was replayed " "since last restartpoint"), errhint("This means that the backup being taken on the standby " "is corrupt and should not be used. " "Enable full_page_writes and run CHECKPOINT on the master, " "and then try an online backup again."))); /* * During recovery, since we don't use the end-of-backup WAL * record and don't write the backup history file, the * starting WAL location doesn't need to be unique. This means * that two base backups started at the same time might use * the same checkpoint as starting locations. */ gotUniqueStartpoint = true; } /* * If two base backups are started at the same time (in WAL sender * processes), we need to make sure that they use different * checkpoints as starting locations, because we use the starting * WAL location as a unique identifier for the base backup in the * end-of-backup WAL record and when we write the backup history * file. Perhaps it would be better generate a separate unique ID * for each backup instead of forcing another checkpoint, but * taking a checkpoint right after another is not that expensive * either because only few buffers have been dirtied yet. */ WALInsertLockAcquireExclusive(); if (XLogCtl->Insert.lastBackupStart < startpoint) { XLogCtl->Insert.lastBackupStart = startpoint; gotUniqueStartpoint = true; } WALInsertLockRelease(); } while (!gotUniqueStartpoint); XLByteToSeg(startpoint, _logSegNo, wal_segment_size); XLogFileName(xlogfilename, starttli, _logSegNo, wal_segment_size); /* * Construct tablespace_map file */ if (exclusive) tblspcmapfile = makeStringInfo(); datadirpathlen = strlen(DataDir); /* Collect information about all tablespaces */ tblspcdir = AllocateDir("pg_tblspc"); while ((de = ReadDir(tblspcdir, "pg_tblspc")) != NULL) { char fullpath[MAXPGPATH + 10]; char linkpath[MAXPGPATH]; char *relpath = NULL; int rllen; StringInfoData buflinkpath; char *s = linkpath; /* Skip special stuff */ if (strcmp(de->d_name, ".") == 0 || strcmp(de->d_name, "..") == 0) continue; snprintf(fullpath, sizeof(fullpath), "pg_tblspc/%s", de->d_name); #if defined(HAVE_READLINK) || defined(WIN32) rllen = readlink(fullpath, linkpath, sizeof(linkpath)); if (rllen < 0) { ereport(WARNING, (errmsg("could not read symbolic link \"%s\": %m", fullpath))); continue; } else if (rllen >= sizeof(linkpath)) { ereport(WARNING, (errmsg("symbolic link \"%s\" target is too long", fullpath))); continue; } linkpath[rllen] = '\0'; /* * Add the escape character '\\' before newline in a string to * ensure that we can distinguish between the newline in the * tablespace path and end of line while reading tablespace_map * file during archive recovery. */ initStringInfo(&buflinkpath); while (*s) { if ((*s == '\n' || *s == '\r') && needtblspcmapfile) appendStringInfoChar(&buflinkpath, '\\'); appendStringInfoChar(&buflinkpath, *s++); } /* * Relpath holds the relative path of the tablespace directory * when it's located within PGDATA, or NULL if it's located * elsewhere. */ if (rllen > datadirpathlen && strncmp(linkpath, DataDir, datadirpathlen) == 0 && IS_DIR_SEP(linkpath[datadirpathlen])) relpath = linkpath + datadirpathlen + 1; ti = palloc(sizeof(tablespaceinfo)); ti->oid = pstrdup(de->d_name); ti->path = pstrdup(buflinkpath.data); ti->rpath = relpath ? pstrdup(relpath) : NULL; ti->size = infotbssize ? sendTablespace(fullpath, true) : -1; if (tablespaces) *tablespaces = lappend(*tablespaces, ti); appendStringInfo(tblspcmapfile, "%s %s\n", ti->oid, ti->path); pfree(buflinkpath.data); #else /* * If the platform does not have symbolic links, it should not be * possible to have tablespaces - clearly somebody else created * them. Warn about it and ignore. */ ereport(WARNING, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("tablespaces are not supported on this platform"))); #endif } FreeDir(tblspcdir); /* * Construct backup label file */ if (exclusive) labelfile = makeStringInfo(); /* Use the log timezone here, not the session timezone */ stamp_time = (pg_time_t) time(NULL); pg_strftime(strfbuf, sizeof(strfbuf), "%Y-%m-%d %H:%M:%S %Z", pg_localtime(&stamp_time, log_timezone)); appendStringInfo(labelfile, "START WAL LOCATION: %X/%X (file %s)\n", (uint32) (startpoint >> 32), (uint32) startpoint, xlogfilename); appendStringInfo(labelfile, "CHECKPOINT LOCATION: %X/%X\n", (uint32) (checkpointloc >> 32), (uint32) checkpointloc); appendStringInfo(labelfile, "BACKUP METHOD: %s\n", exclusive ? "pg_start_backup" : "streamed"); appendStringInfo(labelfile, "BACKUP FROM: %s\n", backup_started_in_recovery ? "standby" : "master"); appendStringInfo(labelfile, "START TIME: %s\n", strfbuf); appendStringInfo(labelfile, "LABEL: %s\n", backupidstr); appendStringInfo(labelfile, "START TIMELINE: %u\n", starttli); /* * Okay, write the file, or return its contents to caller. */ if (exclusive) { /* * Check for existing backup label --- implies a backup is already * running. (XXX given that we checked exclusiveBackupState * above, maybe it would be OK to just unlink any such label * file?) */ if (stat(BACKUP_LABEL_FILE, &stat_buf) != 0) { if (errno != ENOENT) ereport(ERROR, (errcode_for_file_access(), errmsg("could not stat file \"%s\": %m", BACKUP_LABEL_FILE))); } else ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("a backup is already in progress"), errhint("If you're sure there is no backup in progress, remove file \"%s\" and try again.", BACKUP_LABEL_FILE))); fp = AllocateFile(BACKUP_LABEL_FILE, "w"); if (!fp) ereport(ERROR, (errcode_for_file_access(), errmsg("could not create file \"%s\": %m", BACKUP_LABEL_FILE))); if (fwrite(labelfile->data, labelfile->len, 1, fp) != 1 || fflush(fp) != 0 || pg_fsync(fileno(fp)) != 0 || ferror(fp) || FreeFile(fp)) ereport(ERROR, (errcode_for_file_access(), errmsg("could not write file \"%s\": %m", BACKUP_LABEL_FILE))); /* Allocated locally for exclusive backups, so free separately */ pfree(labelfile->data); pfree(labelfile); /* Write backup tablespace_map file. */ if (tblspcmapfile->len > 0) { if (stat(TABLESPACE_MAP, &stat_buf) != 0) { if (errno != ENOENT) ereport(ERROR, (errcode_for_file_access(), errmsg("could not stat file \"%s\": %m", TABLESPACE_MAP))); } else ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("a backup is already in progress"), errhint("If you're sure there is no backup in progress, remove file \"%s\" and try again.", TABLESPACE_MAP))); fp = AllocateFile(TABLESPACE_MAP, "w"); if (!fp) ereport(ERROR, (errcode_for_file_access(), errmsg("could not create file \"%s\": %m", TABLESPACE_MAP))); if (fwrite(tblspcmapfile->data, tblspcmapfile->len, 1, fp) != 1 || fflush(fp) != 0 || pg_fsync(fileno(fp)) != 0 || ferror(fp) || FreeFile(fp)) ereport(ERROR, (errcode_for_file_access(), errmsg("could not write file \"%s\": %m", TABLESPACE_MAP))); } /* Allocated locally for exclusive backups, so free separately */ pfree(tblspcmapfile->data); pfree(tblspcmapfile); } } PG_END_ENSURE_ERROR_CLEANUP(pg_start_backup_callback, (Datum) BoolGetDatum(exclusive)); /* * Mark that start phase has correctly finished for an exclusive backup. * Session-level locks are updated as well to reflect that state. * * Note that CHECK_FOR_INTERRUPTS() must not occur while updating backup * counters and session-level lock. Otherwise they can be updated * inconsistently, and which might cause do_pg_abort_backup() to fail. */ if (exclusive) { WALInsertLockAcquireExclusive(); XLogCtl->Insert.exclusiveBackupState = EXCLUSIVE_BACKUP_IN_PROGRESS; /* Set session-level lock */ sessionBackupState = SESSION_BACKUP_EXCLUSIVE; WALInsertLockRelease(); } else sessionBackupState = SESSION_BACKUP_NON_EXCLUSIVE; /* * We're done. As a convenience, return the starting WAL location. */ if (starttli_p) *starttli_p = starttli; return startpoint; } /* Error cleanup callback for pg_start_backup */ static void pg_start_backup_callback(int code, Datum arg) { bool exclusive = DatumGetBool(arg); /* Update backup counters and forcePageWrites on failure */ WALInsertLockAcquireExclusive(); if (exclusive) { Assert(XLogCtl->Insert.exclusiveBackupState == EXCLUSIVE_BACKUP_STARTING); XLogCtl->Insert.exclusiveBackupState = EXCLUSIVE_BACKUP_NONE; } else { Assert(XLogCtl->Insert.nonExclusiveBackups > 0); XLogCtl->Insert.nonExclusiveBackups--; } if (XLogCtl->Insert.exclusiveBackupState == EXCLUSIVE_BACKUP_NONE && XLogCtl->Insert.nonExclusiveBackups == 0) { XLogCtl->Insert.forcePageWrites = false; } WALInsertLockRelease(); } /* * Error cleanup callback for pg_stop_backup */ static void pg_stop_backup_callback(int code, Datum arg) { bool exclusive = DatumGetBool(arg); /* Update backup status on failure */ WALInsertLockAcquireExclusive(); if (exclusive) { Assert(XLogCtl->Insert.exclusiveBackupState == EXCLUSIVE_BACKUP_STOPPING); XLogCtl->Insert.exclusiveBackupState = EXCLUSIVE_BACKUP_IN_PROGRESS; } WALInsertLockRelease(); } /* * Utility routine to fetch the session-level status of a backup running. */ SessionBackupState get_backup_status(void) { return sessionBackupState; } /* * do_pg_stop_backup * * Utility function called at the end of an online backup. It cleans up the * backup state and can optionally wait for WAL segments to be archived. * * If labelfile is NULL, this stops an exclusive backup. Otherwise this stops * the non-exclusive backup specified by 'labelfile'. * * Returns the last WAL location that must be present to restore from this * backup, and the corresponding timeline ID in *stoptli_p. * * It is the responsibility of the caller of this function to verify the * permissions of the calling user! */ XLogRecPtr do_pg_stop_backup(char *labelfile, bool waitforarchive, TimeLineID *stoptli_p) { bool exclusive = (labelfile == NULL); bool backup_started_in_recovery = false; XLogRecPtr startpoint; XLogRecPtr stoppoint; TimeLineID stoptli; pg_time_t stamp_time; char strfbuf[128]; char histfilepath[MAXPGPATH]; char startxlogfilename[MAXFNAMELEN]; char stopxlogfilename[MAXFNAMELEN]; char lastxlogfilename[MAXFNAMELEN]; char histfilename[MAXFNAMELEN]; char backupfrom[20]; XLogSegNo _logSegNo; FILE *lfp; FILE *fp; char ch; int seconds_before_warning; int waits = 0; bool reported_waiting = false; char *remaining; char *ptr; uint32 hi, lo; backup_started_in_recovery = RecoveryInProgress(); /* * Currently only non-exclusive backup can be taken during recovery. */ if (backup_started_in_recovery && exclusive) ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("recovery is in progress"), errhint("WAL control functions cannot be executed during recovery."))); /* * During recovery, we don't need to check WAL level. Because, if WAL * level is not sufficient, it's impossible to get here during recovery. */ if (!backup_started_in_recovery && !XLogIsNeeded()) ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("WAL level not sufficient for making an online backup"), errhint("wal_level must be set to \"replica\" or \"logical\" at server start."))); if (exclusive) { /* * At first, mark that we're now stopping an exclusive backup, to * ensure that there are no other sessions currently running * pg_start_backup() or pg_stop_backup(). */ WALInsertLockAcquireExclusive(); if (XLogCtl->Insert.exclusiveBackupState != EXCLUSIVE_BACKUP_IN_PROGRESS) { WALInsertLockRelease(); ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("exclusive backup not in progress"))); } XLogCtl->Insert.exclusiveBackupState = EXCLUSIVE_BACKUP_STOPPING; WALInsertLockRelease(); /* * Remove backup_label. In case of failure, the state for an exclusive * backup is switched back to in-progress. */ PG_ENSURE_ERROR_CLEANUP(pg_stop_backup_callback, (Datum) BoolGetDatum(exclusive)); { /* * Read the existing label file into memory. */ struct stat statbuf; int r; if (stat(BACKUP_LABEL_FILE, &statbuf)) { /* should not happen per the upper checks */ if (errno != ENOENT) ereport(ERROR, (errcode_for_file_access(), errmsg("could not stat file \"%s\": %m", BACKUP_LABEL_FILE))); ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("a backup is not in progress"))); } lfp = AllocateFile(BACKUP_LABEL_FILE, "r"); if (!lfp) { ereport(ERROR, (errcode_for_file_access(), errmsg("could not read file \"%s\": %m", BACKUP_LABEL_FILE))); } labelfile = palloc(statbuf.st_size + 1); r = fread(labelfile, statbuf.st_size, 1, lfp); labelfile[statbuf.st_size] = '\0'; /* * Close and remove the backup label file */ if (r != 1 || ferror(lfp) || FreeFile(lfp)) ereport(ERROR, (errcode_for_file_access(), errmsg("could not read file \"%s\": %m", BACKUP_LABEL_FILE))); durable_unlink(BACKUP_LABEL_FILE, ERROR); /* * Remove tablespace_map file if present, it is created only if * there are tablespaces. */ durable_unlink(TABLESPACE_MAP, DEBUG1); } PG_END_ENSURE_ERROR_CLEANUP(pg_stop_backup_callback, (Datum) BoolGetDatum(exclusive)); } /* * OK to update backup counters, forcePageWrites and session-level lock. * * Note that CHECK_FOR_INTERRUPTS() must not occur while updating them. * Otherwise they can be updated inconsistently, and which might cause * do_pg_abort_backup() to fail. */ WALInsertLockAcquireExclusive(); if (exclusive) { XLogCtl->Insert.exclusiveBackupState = EXCLUSIVE_BACKUP_NONE; } else { /* * The user-visible pg_start/stop_backup() functions that operate on * exclusive backups can be called at any time, but for non-exclusive * backups, it is expected that each do_pg_start_backup() call is * matched by exactly one do_pg_stop_backup() call. */ Assert(XLogCtl->Insert.nonExclusiveBackups > 0); XLogCtl->Insert.nonExclusiveBackups--; } if (XLogCtl->Insert.exclusiveBackupState == EXCLUSIVE_BACKUP_NONE && XLogCtl->Insert.nonExclusiveBackups == 0) { XLogCtl->Insert.forcePageWrites = false; } /* * Clean up session-level lock. * * You might think that WALInsertLockRelease() can be called before * cleaning up session-level lock because session-level lock doesn't need * to be protected with WAL insertion lock. But since * CHECK_FOR_INTERRUPTS() can occur in it, session-level lock must be * cleaned up before it. */ sessionBackupState = SESSION_BACKUP_NONE; WALInsertLockRelease(); /* * Read and parse the START WAL LOCATION line (this code is pretty crude, * but we are not expecting any variability in the file format). */ if (sscanf(labelfile, "START WAL LOCATION: %X/%X (file %24s)%c", &hi, &lo, startxlogfilename, &ch) != 4 || ch != '\n') ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("invalid data in file \"%s\"", BACKUP_LABEL_FILE))); startpoint = ((uint64) hi) << 32 | lo; remaining = strchr(labelfile, '\n') + 1; /* %n is not portable enough */ /* * Parse the BACKUP FROM line. If we are taking an online backup from the * standby, we confirm that the standby has not been promoted during the * backup. */ ptr = strstr(remaining, "BACKUP FROM:"); if (!ptr || sscanf(ptr, "BACKUP FROM: %19s\n", backupfrom) != 1) ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("invalid data in file \"%s\"", BACKUP_LABEL_FILE))); if (strcmp(backupfrom, "standby") == 0 && !backup_started_in_recovery) ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("the standby was promoted during online backup"), errhint("This means that the backup being taken is corrupt " "and should not be used. " "Try taking another online backup."))); /* * During recovery, we don't write an end-of-backup record. We assume that * pg_control was backed up last and its minimum recovery point can be * available as the backup end location. Since we don't have an * end-of-backup record, we use the pg_control value to check whether * we've reached the end of backup when starting recovery from this * backup. We have no way of checking if pg_control wasn't backed up last * however. * * We don't force a switch to new WAL file but it is still possible to * wait for all the required files to be archived if waitforarchive is * true. This is okay if we use the backup to start a standby and fetch * the missing WAL using streaming replication. But in the case of an * archive recovery, a user should set waitforarchive to true and wait for * them to be archived to ensure that all the required files are * available. * * We return the current minimum recovery point as the backup end * location. Note that it can be greater than the exact backup end * location if the minimum recovery point is updated after the backup of * pg_control. This is harmless for current uses. * * XXX currently a backup history file is for informational and debug * purposes only. It's not essential for an online backup. Furthermore, * even if it's created, it will not be archived during recovery because * an archiver is not invoked. So it doesn't seem worthwhile to write a * backup history file during recovery. */ if (backup_started_in_recovery) { XLogRecPtr recptr; /* * Check to see if all WAL replayed during online backup contain * full-page writes. */ SpinLockAcquire(&XLogCtl->info_lck); recptr = XLogCtl->lastFpwDisableRecPtr; SpinLockRelease(&XLogCtl->info_lck); if (startpoint <= recptr) ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("WAL generated with full_page_writes=off was replayed " "during online backup"), errhint("This means that the backup being taken on the standby " "is corrupt and should not be used. " "Enable full_page_writes and run CHECKPOINT on the master, " "and then try an online backup again."))); LWLockAcquire(ControlFileLock, LW_SHARED); stoppoint = ControlFile->minRecoveryPoint; stoptli = ControlFile->minRecoveryPointTLI; LWLockRelease(ControlFileLock); } else { /* * Write the backup-end xlog record */ XLogBeginInsert(); XLogRegisterData((char *) (&startpoint), sizeof(startpoint)); stoppoint = XLogInsert(RM_XLOG_ID, XLOG_BACKUP_END); stoptli = ThisTimeLineID; /* * Force a switch to a new xlog segment file, so that the backup is * valid as soon as archiver moves out the current segment file. */ RequestXLogSwitch(false); XLByteToPrevSeg(stoppoint, _logSegNo, wal_segment_size); XLogFileName(stopxlogfilename, stoptli, _logSegNo, wal_segment_size); /* Use the log timezone here, not the session timezone */ stamp_time = (pg_time_t) time(NULL); pg_strftime(strfbuf, sizeof(strfbuf), "%Y-%m-%d %H:%M:%S %Z", pg_localtime(&stamp_time, log_timezone)); /* * Write the backup history file */ XLByteToSeg(startpoint, _logSegNo, wal_segment_size); BackupHistoryFilePath(histfilepath, stoptli, _logSegNo, startpoint, wal_segment_size); fp = AllocateFile(histfilepath, "w"); if (!fp) ereport(ERROR, (errcode_for_file_access(), errmsg("could not create file \"%s\": %m", histfilepath))); fprintf(fp, "START WAL LOCATION: %X/%X (file %s)\n", (uint32) (startpoint >> 32), (uint32) startpoint, startxlogfilename); fprintf(fp, "STOP WAL LOCATION: %X/%X (file %s)\n", (uint32) (stoppoint >> 32), (uint32) stoppoint, stopxlogfilename); /* * Transfer remaining lines including label and start timeline to * history file. */ fprintf(fp, "%s", remaining); fprintf(fp, "STOP TIME: %s\n", strfbuf); fprintf(fp, "STOP TIMELINE: %u\n", stoptli); if (fflush(fp) || ferror(fp) || FreeFile(fp)) ereport(ERROR, (errcode_for_file_access(), errmsg("could not write file \"%s\": %m", histfilepath))); /* * Clean out any no-longer-needed history files. As a side effect, * this will post a .ready file for the newly created history file, * notifying the archiver that history file may be archived * immediately. */ CleanupBackupHistory(); } /* * If archiving is enabled, wait for all the required WAL files to be * archived before returning. If archiving isn't enabled, the required WAL * needs to be transported via streaming replication (hopefully with * wal_keep_segments set high enough), or some more exotic mechanism like * polling and copying files from pg_wal with script. We have no knowledge * of those mechanisms, so it's up to the user to ensure that he gets all * the required WAL. * * We wait until both the last WAL file filled during backup and the * history file have been archived, and assume that the alphabetic sorting * property of the WAL files ensures any earlier WAL files are safely * archived as well. * * We wait forever, since archive_command is supposed to work and we * assume the admin wanted his backup to work completely. If you don't * wish to wait, then either waitforarchive should be passed in as false, * or you can set statement_timeout. Also, some notices are issued to * clue in anyone who might be doing this interactively. */ if (waitforarchive && ((!backup_started_in_recovery && XLogArchivingActive()) || (backup_started_in_recovery && XLogArchivingAlways()))) { XLByteToPrevSeg(stoppoint, _logSegNo, wal_segment_size); XLogFileName(lastxlogfilename, stoptli, _logSegNo, wal_segment_size); XLByteToSeg(startpoint, _logSegNo, wal_segment_size); BackupHistoryFileName(histfilename, stoptli, _logSegNo, startpoint, wal_segment_size); seconds_before_warning = 60; waits = 0; while (XLogArchiveIsBusy(lastxlogfilename) || XLogArchiveIsBusy(histfilename)) { CHECK_FOR_INTERRUPTS(); if (!reported_waiting && waits > 5) { ereport(NOTICE, (errmsg("base backup done, waiting for required WAL segments to be archived"))); reported_waiting = true; } pg_usleep(1000000L); if (++waits >= seconds_before_warning) { seconds_before_warning *= 2; /* This wraps in >10 years... */ ereport(WARNING, (errmsg("still waiting for all required WAL segments to be archived (%d seconds elapsed)", waits), errhint("Check that your archive_command is executing properly. " "You can safely cancel this backup, " "but the database backup will not be usable without all the WAL segments."))); } } ereport(NOTICE, (errmsg("all required WAL segments have been archived"))); } else if (waitforarchive) ereport(NOTICE, (errmsg("WAL archiving is not enabled; you must ensure that all required WAL segments are copied through other means to complete the backup"))); /* * We're done. As a convenience, return the ending WAL location. */ if (stoptli_p) *stoptli_p = stoptli; return stoppoint; } /* * do_pg_abort_backup: abort a running backup * * This does just the most basic steps of do_pg_stop_backup(), by taking the * system out of backup mode, thus making it a lot more safe to call from * an error handler. * * The caller can pass 'arg' as 'true' or 'false' to control whether a warning * is emitted. * * NB: This is only for aborting a non-exclusive backup that doesn't write * backup_label. A backup started with pg_start_backup() needs to be finished * with pg_stop_backup(). * * NB: This gets used as a before_shmem_exit handler, hence the odd-looking * signature. */ void do_pg_abort_backup(int code, Datum arg) { bool emit_warning = DatumGetBool(arg); /* * Quick exit if session is not keeping around a non-exclusive backup * already started. */ if (sessionBackupState != SESSION_BACKUP_NON_EXCLUSIVE) return; WALInsertLockAcquireExclusive(); Assert(XLogCtl->Insert.nonExclusiveBackups > 0); XLogCtl->Insert.nonExclusiveBackups--; if (XLogCtl->Insert.exclusiveBackupState == EXCLUSIVE_BACKUP_NONE && XLogCtl->Insert.nonExclusiveBackups == 0) { XLogCtl->Insert.forcePageWrites = false; } WALInsertLockRelease(); if (emit_warning) ereport(WARNING, (errmsg("aborting backup due to backend exiting before pg_stop_back up was called"))); } /* * Register a handler that will warn about unterminated backups at end of * session, unless this has already been done. */ void register_persistent_abort_backup_handler(void) { static bool already_done = false; if (already_done) return; before_shmem_exit(do_pg_abort_backup, DatumGetBool(true)); already_done = true; } /* * Get latest redo apply position. * * Exported to allow WALReceiver to read the pointer directly. */ XLogRecPtr GetXLogReplayRecPtr(TimeLineID *replayTLI) { XLogRecPtr recptr; TimeLineID tli; SpinLockAcquire(&XLogCtl->info_lck); recptr = XLogCtl->lastReplayedEndRecPtr; tli = XLogCtl->lastReplayedTLI; SpinLockRelease(&XLogCtl->info_lck); if (replayTLI) *replayTLI = tli; return recptr; } /* * Get latest WAL insert pointer */ XLogRecPtr GetXLogInsertRecPtr(void) { XLogCtlInsert *Insert = &XLogCtl->Insert; uint64 current_bytepos; SpinLockAcquire(&Insert->insertpos_lck); current_bytepos = Insert->CurrBytePos; SpinLockRelease(&Insert->insertpos_lck); return XLogBytePosToRecPtr(current_bytepos); } /* * Get latest WAL write pointer */ XLogRecPtr GetXLogWriteRecPtr(void) { SpinLockAcquire(&XLogCtl->info_lck); LogwrtResult = XLogCtl->LogwrtResult; SpinLockRelease(&XLogCtl->info_lck); return LogwrtResult.Write; } /* * Returns the redo pointer of the last checkpoint or restartpoint. This is * the oldest point in WAL that we still need, if we have to restart recovery. */ void GetOldestRestartPoint(XLogRecPtr *oldrecptr, TimeLineID *oldtli) { LWLockAcquire(ControlFileLock, LW_SHARED); *oldrecptr = ControlFile->checkPointCopy.redo; *oldtli = ControlFile->checkPointCopy.ThisTimeLineID; LWLockRelease(ControlFileLock); } /* * read_backup_label: check to see if a backup_label file is present * * If we see a backup_label during recovery, we assume that we are recovering * from a backup dump file, and we therefore roll forward from the checkpoint * identified by the label file, NOT what pg_control says. This avoids the * problem that pg_control might have been archived one or more checkpoints * later than the start of the dump, and so if we rely on it as the start * point, we will fail to restore a consistent database state. * * Returns true if a backup_label was found (and fills the checkpoint * location and its REDO location into *checkPointLoc and RedoStartLSN, * respectively); returns false if not. If this backup_label came from a * streamed backup, *backupEndRequired is set to true. If this backup_label * was created during recovery, *backupFromStandby is set to true. */ static bool read_backup_label(XLogRecPtr *checkPointLoc, bool *backupEndRequired, bool *backupFromStandby) { char startxlogfilename[MAXFNAMELEN]; TimeLineID tli_from_walseg, tli_from_file; FILE *lfp; char ch; char backuptype[20]; char backupfrom[20]; char backuplabel[MAXPGPATH]; char backuptime[128]; uint32 hi, lo; *backupEndRequired = false; *backupFromStandby = false; /* * See if label file is present */ lfp = AllocateFile(BACKUP_LABEL_FILE, "r"); if (!lfp) { if (errno != ENOENT) ereport(FATAL, (errcode_for_file_access(), errmsg("could not read file \"%s\": %m", BACKUP_LABEL_FILE))); return false; /* it's not there, all is fine */ } /* * Read and parse the START WAL LOCATION and CHECKPOINT lines (this code * is pretty crude, but we are not expecting any variability in the file * format). */ if (fscanf(lfp, "START WAL LOCATION: %X/%X (file %08X%16s)%c", &hi, &lo, &tli_from_walseg, startxlogfilename, &ch) != 5 || ch != '\n') ereport(FATAL, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("invalid data in file \"%s\"", BACKUP_LABEL_FILE))); RedoStartLSN = ((uint64) hi) << 32 | lo; if (fscanf(lfp, "CHECKPOINT LOCATION: %X/%X%c", &hi, &lo, &ch) != 3 || ch != '\n') ereport(FATAL, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("invalid data in file \"%s\"", BACKUP_LABEL_FILE))); *checkPointLoc = ((uint64) hi) << 32 | lo; /* * BACKUP METHOD and BACKUP FROM lines are new in 9.2. We can't restore * from an older backup anyway, but since the information on it is not * strictly required, don't error out if it's missing for some reason. */ if (fscanf(lfp, "BACKUP METHOD: %19s\n", backuptype) == 1) { if (strcmp(backuptype, "streamed") == 0) *backupEndRequired = true; } if (fscanf(lfp, "BACKUP FROM: %19s\n", backupfrom) == 1) { if (strcmp(backupfrom, "standby") == 0) *backupFromStandby = true; } /* * Parse START TIME and LABEL. Those are not mandatory fields for recovery * but checking for their presence is useful for debugging and the next * sanity checks. Cope also with the fact that the result buffers have a * pre-allocated size, hence if the backup_label file has been generated * with strings longer than the maximum assumed here an incorrect parsing * happens. That's fine as only minor consistency checks are done * afterwards. */ if (fscanf(lfp, "START TIME: %127[^\n]\n", backuptime) == 1) ereport(DEBUG1, (errmsg("backup time %s in file \"%s\"", backuptime, BACKUP_LABEL_FILE))); if (fscanf(lfp, "LABEL: %1023[^\n]\n", backuplabel) == 1) ereport(DEBUG1, (errmsg("backup label %s in file \"%s\"", backuplabel, BACKUP_LABEL_FILE))); /* * START TIMELINE is new as of 11. Its parsing is not mandatory, still use * it as a sanity check if present. */ if (fscanf(lfp, "START TIMELINE: %u\n", &tli_from_file) == 1) { if (tli_from_walseg != tli_from_file) ereport(FATAL, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("invalid data in file \"%s\"", BACKUP_LABEL_FILE), errdetail("Timeline ID parsed is %u, but expected %u.", tli_from_file, tli_from_walseg))); ereport(DEBUG1, (errmsg("backup timeline %u in file \"%s\"", tli_from_file, BACKUP_LABEL_FILE))); } if (ferror(lfp) || FreeFile(lfp)) ereport(FATAL, (errcode_for_file_access(), errmsg("could not read file \"%s\": %m", BACKUP_LABEL_FILE))); return true; } /* * read_tablespace_map: check to see if a tablespace_map file is present * * If we see a tablespace_map file during recovery, we assume that we are * recovering from a backup dump file, and we therefore need to create symlinks * as per the information present in tablespace_map file. * * Returns true if a tablespace_map file was found (and fills the link * information for all the tablespace links present in file); returns false * if not. */ static bool read_tablespace_map(List **tablespaces) { tablespaceinfo *ti; FILE *lfp; char tbsoid[MAXPGPATH]; char *tbslinkpath; char str[MAXPGPATH]; int ch, prev_ch = -1, i = 0, n; /* * See if tablespace_map file is present */ lfp = AllocateFile(TABLESPACE_MAP, "r"); if (!lfp) { if (errno != ENOENT) ereport(FATAL, (errcode_for_file_access(), errmsg("could not read file \"%s\": %m", TABLESPACE_MAP))); return false; /* it's not there, all is fine */ } /* * Read and parse the link name and path lines from tablespace_map file * (this code is pretty crude, but we are not expecting any variability in * the file format). While taking backup we embed escape character '\\' * before newline in tablespace path, so that during reading of * tablespace_map file, we could distinguish newline in tablespace path * and end of line. Now while reading tablespace_map file, remove the * escape character that has been added in tablespace path during backup. */ while ((ch = fgetc(lfp)) != EOF) { if ((ch == '\n' || ch == '\r') && prev_ch != '\\') { str[i] = '\0'; if (sscanf(str, "%s %n", tbsoid, &n) != 1) ereport(FATAL, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("invalid data in file \"%s\"", TABLESPACE_MAP))); tbslinkpath = str + n; i = 0; ti = palloc(sizeof(tablespaceinfo)); ti->oid = pstrdup(tbsoid); ti->path = pstrdup(tbslinkpath); *tablespaces = lappend(*tablespaces, ti); continue; } else if ((ch == '\n' || ch == '\r') && prev_ch == '\\') str[i - 1] = ch; else str[i++] = ch; prev_ch = ch; } if (ferror(lfp) || FreeFile(lfp)) ereport(FATAL, (errcode_for_file_access(), errmsg("could not read file \"%s\": %m", TABLESPACE_MAP))); return true; } /* * Error context callback for errors occurring during rm_redo(). */ static void rm_redo_error_callback(void *arg) { XLogReaderState *record = (XLogReaderState *) arg; StringInfoData buf; initStringInfo(&buf); xlog_outdesc(&buf, record); /* translator: %s is a WAL record description */ errcontext("WAL redo at %X/%X for %s", (uint32) (record->ReadRecPtr >> 32), (uint32) record->ReadRecPtr, buf.data); pfree(buf.data); } /* * BackupInProgress: check if online backup mode is active * * This is done by checking for existence of the "backup_label" file. */ bool BackupInProgress(void) { struct stat stat_buf; return (stat(BACKUP_LABEL_FILE, &stat_buf) == 0); } /* * CancelBackup: rename the "backup_label" and "tablespace_map" * files to cancel backup mode * * If the "backup_label" file exists, it will be renamed to "backup_label.old". * Similarly, if the "tablespace_map" file exists, it will be renamed to * "tablespace_map.old". * * Note that this will render an online backup in progress * useless. To correctly finish an online backup, pg_stop_backup must be * called. */ void CancelBackup(void) { struct stat stat_buf; /* if the backup_label file is not there, return */ if (stat(BACKUP_LABEL_FILE, &stat_buf) < 0) return; /* remove leftover file from previously canceled backup if it exists */ unlink(BACKUP_LABEL_OLD); if (durable_rename(BACKUP_LABEL_FILE, BACKUP_LABEL_OLD, DEBUG1) != 0) { ereport(WARNING, (errcode_for_file_access(), errmsg("online backup mode was not canceled"), errdetail("File \"%s\" could not be renamed to \"%s\": %m.", BACKUP_LABEL_FILE, BACKUP_LABEL_OLD))); return; } /* if the tablespace_map file is not there, return */ if (stat(TABLESPACE_MAP, &stat_buf) < 0) { ereport(LOG, (errmsg("online backup mode canceled"), errdetail("File \"%s\" was renamed to \"%s\".", BACKUP_LABEL_FILE, BACKUP_LABEL_OLD))); return; } /* remove leftover file from previously canceled backup if it exists */ unlink(TABLESPACE_MAP_OLD); if (durable_rename(TABLESPACE_MAP, TABLESPACE_MAP_OLD, DEBUG1) == 0) { ereport(LOG, (errmsg("online backup mode canceled"), errdetail("Files \"%s\" and \"%s\" were renamed to " "\"%s\" and \"%s\", respectively.", BACKUP_LABEL_FILE, TABLESPACE_MAP, BACKUP_LABEL_OLD, TABLESPACE_MAP_OLD))); } else { ereport(WARNING, (errcode_for_file_access(), errmsg("online backup mode canceled"), errdetail("File \"%s\" was renamed to \"%s\", but " "file \"%s\" could not be renamed to \"%s\": %m.", BACKUP_LABEL_FILE, BACKUP_LABEL_OLD, TABLESPACE_MAP, TABLESPACE_MAP_OLD))); } } /* * Read the XLOG page containing RecPtr into readBuf (if not read already). * Returns number of bytes read, if the page is read successfully, or -1 * in case of errors. When errors occur, they are ereport'ed, but only * if they have not been previously reported. * * This is responsible for restoring files from archive as needed, as well * as for waiting for the requested WAL record to arrive in standby mode. * * 'emode' specifies the log level used for reporting "file not found" or * "end of WAL" situations in archive recovery, or in standby mode when a * trigger file is found. If set to WARNING or below, XLogPageRead() returns * false in those situations, on higher log levels the ereport() won't * return. * * In standby mode, if after a successful return of XLogPageRead() the * caller finds the record it's interested in to be broken, it should * ereport the error with the level determined by * emode_for_corrupt_record(), and then set lastSourceFailed * and call XLogPageRead() again with the same arguments. This lets * XLogPageRead() to try fetching the record from another source, or to * sleep and retry. */ static int XLogPageRead(XLogReaderState *xlogreader, XLogRecPtr targetPagePtr, int reqLen, XLogRecPtr targetRecPtr, char *readBuf) { XLogPageReadPrivate *private = (XLogPageReadPrivate *) xlogreader->private_data; int emode = private->emode; uint32 targetPageOff; XLogSegNo targetSegNo PG_USED_FOR_ASSERTS_ONLY; int r; XLByteToSeg(targetPagePtr, targetSegNo, wal_segment_size); targetPageOff = XLogSegmentOffset(targetPagePtr, wal_segment_size); /* * See if we need to switch to a new segment because the requested record * is not in the currently open one. */ if (readFile >= 0 && !XLByteInSeg(targetPagePtr, readSegNo, wal_segment_size)) { /* * Request a restartpoint if we've replayed too much xlog since the * last one. */ if (bgwriterLaunched) { if (XLogCheckpointNeeded(readSegNo)) { (void) GetRedoRecPtr(); if (XLogCheckpointNeeded(readSegNo)) RequestCheckpoint(CHECKPOINT_CAUSE_XLOG); } } close(readFile); readFile = -1; readSource = 0; } XLByteToSeg(targetPagePtr, readSegNo, wal_segment_size); retry: /* See if we need to retrieve more data */ if (readFile < 0 || (readSource == XLOG_FROM_STREAM && receivedUpto < targetPagePtr + reqLen)) { if (!WaitForWALToBecomeAvailable(targetPagePtr + reqLen, private->randAccess, private->fetching_ckpt, targetRecPtr)) { if (readFile >= 0) close(readFile); readFile = -1; readLen = 0; readSource = 0; return -1; } } /* * At this point, we have the right segment open and if we're streaming we * know the requested record is in it. */ Assert(readFile != -1); /* * If the current segment is being streamed from master, calculate how * much of the current page we have received already. We know the * requested record has been received, but this is for the benefit of * future calls, to allow quick exit at the top of this function. */ if (readSource == XLOG_FROM_STREAM) { if (((targetPagePtr) / XLOG_BLCKSZ) != (receivedUpto / XLOG_BLCKSZ)) readLen = XLOG_BLCKSZ; else readLen = XLogSegmentOffset(receivedUpto, wal_segment_size) - targetPageOff; } else readLen = XLOG_BLCKSZ; /* Read the requested page */ readOff = targetPageOff; pgstat_report_wait_start(WAIT_EVENT_WAL_READ); r = pg_pread(readFile, readBuf, XLOG_BLCKSZ, (off_t) readOff); if (r != XLOG_BLCKSZ) { char fname[MAXFNAMELEN]; int save_errno = errno; pgstat_report_wait_end(); XLogFileName(fname, curFileTLI, readSegNo, wal_segment_size); if (r < 0) { errno = save_errno; ereport(emode_for_corrupt_record(emode, targetPagePtr + reqLen), (errcode_for_file_access(), errmsg("could not read from log segment %s, offset %u: %m", fname, readOff))); } else ereport(emode_for_corrupt_record(emode, targetPagePtr + reqLen), (errcode(ERRCODE_DATA_CORRUPTED), errmsg("could not read from log segment %s, offset %u: read %d of %zu", fname, readOff, r, (Size) XLOG_BLCKSZ))); goto next_record_is_invalid; } pgstat_report_wait_end(); Assert(targetSegNo == readSegNo); Assert(targetPageOff == readOff); Assert(reqLen <= readLen); xlogreader->seg.ws_tli = curFileTLI; /* * Check the page header immediately, so that we can retry immediately if * it's not valid. This may seem unnecessary, because XLogReadRecord() * validates the page header anyway, and would propagate the failure up to * ReadRecord(), which would retry. However, there's a corner case with * continuation records, if a record is split across two pages such that * we would need to read the two pages from different sources. For * example, imagine a scenario where a streaming replica is started up, * and replay reaches a record that's split across two WAL segments. The * first page is only available locally, in pg_wal, because it's already * been recycled in the master. The second page, however, is not present * in pg_wal, and we should stream it from the master. There is a recycled * WAL segment present in pg_wal, with garbage contents, however. We would * read the first page from the local WAL segment, but when reading the * second page, we would read the bogus, recycled, WAL segment. If we * didn't catch that case here, we would never recover, because * ReadRecord() would retry reading the whole record from the beginning. * * Of course, this only catches errors in the page header, which is what * happens in the case of a recycled WAL segment. Other kinds of errors or * corruption still has the same problem. But this at least fixes the * common case, which can happen as part of normal operation. * * Validating the page header is cheap enough that doing it twice * shouldn't be a big deal from a performance point of view. */ if (!XLogReaderValidatePageHeader(xlogreader, targetPagePtr, readBuf)) { /* reset any error XLogReaderValidatePageHeader() might have set */ xlogreader->errormsg_buf[0] = '\0'; goto next_record_is_invalid; } return readLen; next_record_is_invalid: lastSourceFailed = true; if (readFile >= 0) close(readFile); readFile = -1; readLen = 0; readSource = 0; /* In standby-mode, keep trying */ if (StandbyMode) goto retry; else return -1; } /* * Open the WAL segment containing WAL location 'RecPtr'. * * The segment can be fetched via restore_command, or via walreceiver having * streamed the record, or it can already be present in pg_wal. Checking * pg_wal is mainly for crash recovery, but it will be polled in standby mode * too, in case someone copies a new segment directly to pg_wal. That is not * documented or recommended, though. * * If 'fetching_ckpt' is true, we're fetching a checkpoint record, and should * prepare to read WAL starting from RedoStartLSN after this. * * 'RecPtr' might not point to the beginning of the record we're interested * in, it might also point to the page or segment header. In that case, * 'tliRecPtr' is the position of the WAL record we're interested in. It is * used to decide which timeline to stream the requested WAL from. * * If the record is not immediately available, the function returns false * if we're not in standby mode. In standby mode, waits for it to become * available. * * When the requested record becomes available, the function opens the file * containing it (if not open already), and returns true. When end of standby * mode is triggered by the user, and there is no more WAL available, returns * false. */ static bool WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess, bool fetching_ckpt, XLogRecPtr tliRecPtr) { static TimestampTz last_fail_time = 0; TimestampTz now; bool streaming_reply_sent = false; /*------- * Standby mode is implemented by a state machine: * * 1. Read from either archive or pg_wal (XLOG_FROM_ARCHIVE), or just * pg_wal (XLOG_FROM_PG_WAL) * 2. Check trigger file * 3. Read from primary server via walreceiver (XLOG_FROM_STREAM) * 4. Rescan timelines * 5. Sleep wal_retrieve_retry_interval milliseconds, and loop back to 1. * * Failure to read from the current source advances the state machine to * the next state. * * 'currentSource' indicates the current state. There are no currentSource * values for "check trigger", "rescan timelines", and "sleep" states, * those actions are taken when reading from the previous source fails, as * part of advancing to the next state. *------- */ if (!InArchiveRecovery) currentSource = XLOG_FROM_PG_WAL; else if (currentSource == 0) currentSource = XLOG_FROM_ARCHIVE; for (;;) { int oldSource = currentSource; /* * First check if we failed to read from the current source, and * advance the state machine if so. The failure to read might've * happened outside this function, e.g when a CRC check fails on a * record, or within this loop. */ if (lastSourceFailed) { switch (currentSource) { case XLOG_FROM_ARCHIVE: case XLOG_FROM_PG_WAL: /* * Check to see if the trigger file exists. Note that we * do this only after failure, so when you create the * trigger file, we still finish replaying as much as we * can from archive and pg_wal before failover. */ if (StandbyMode && CheckForStandbyTrigger()) { ShutdownWalRcv(); return false; } /* * Not in standby mode, and we've now tried the archive * and pg_wal. */ if (!StandbyMode) return false; /* * If primary_conninfo is set, launch walreceiver to try * to stream the missing WAL. * * If fetching_ckpt is true, RecPtr points to the initial * checkpoint location. In that case, we use RedoStartLSN * as the streaming start position instead of RecPtr, so * that when we later jump backwards to start redo at * RedoStartLSN, we will have the logs streamed already. */ if (PrimaryConnInfo && strcmp(PrimaryConnInfo, "") != 0) { XLogRecPtr ptr; TimeLineID tli; if (fetching_ckpt) { ptr = RedoStartLSN; tli = ControlFile->checkPointCopy.ThisTimeLineID; } else { ptr = RecPtr; /* * Use the record begin position to determine the * TLI, rather than the position we're reading. */ tli = tliOfPointInHistory(tliRecPtr, expectedTLEs); if (curFileTLI > 0 && tli < curFileTLI) elog(ERROR, "according to history file, WAL location %X/%X belongs to timeline %u, but previous recovered WAL file came from timeline %u", (uint32) (tliRecPtr >> 32), (uint32) tliRecPtr, tli, curFileTLI); } curFileTLI = tli; RequestXLogStreaming(tli, ptr, PrimaryConnInfo, PrimarySlotName); receivedUpto = 0; } /* * Move to XLOG_FROM_STREAM state in either case. We'll * get immediate failure if we didn't launch walreceiver, * and move on to the next state. */ currentSource = XLOG_FROM_STREAM; break; case XLOG_FROM_STREAM: /* * Failure while streaming. Most likely, we got here * because streaming replication was terminated, or * promotion was triggered. But we also get here if we * find an invalid record in the WAL streamed from master, * in which case something is seriously wrong. There's * little chance that the problem will just go away, but * PANIC is not good for availability either, especially * in hot standby mode. So, we treat that the same as * disconnection, and retry from archive/pg_wal again. The * WAL in the archive should be identical to what was * streamed, so it's unlikely that it helps, but one can * hope... */ /* * We should be able to move to XLOG_FROM_STREAM * only in standby mode. */ Assert(StandbyMode); /* * Before we leave XLOG_FROM_STREAM state, make sure that * walreceiver is not active, so that it won't overwrite * WAL that we restore from archive. */ if (WalRcvStreaming()) ShutdownWalRcv(); /* * Before we sleep, re-scan for possible new timelines if * we were requested to recover to the latest timeline. */ if (recoveryTargetTimeLineGoal == RECOVERY_TARGET_TIMELINE_LATEST) { if (rescanLatestTimeLine()) { currentSource = XLOG_FROM_ARCHIVE; break; } } /* * XLOG_FROM_STREAM is the last state in our state * machine, so we've exhausted all the options for * obtaining the requested WAL. We're going to loop back * and retry from the archive, but if it hasn't been long * since last attempt, sleep wal_retrieve_retry_interval * milliseconds to avoid busy-waiting. */ now = GetCurrentTimestamp(); if (!TimestampDifferenceExceeds(last_fail_time, now, wal_retrieve_retry_interval)) { long secs, wait_time; int usecs; TimestampDifference(last_fail_time, now, &secs, &usecs); wait_time = wal_retrieve_retry_interval - (secs * 1000 + usecs / 1000); (void) WaitLatch(&XLogCtl->recoveryWakeupLatch, WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH, wait_time, WAIT_EVENT_RECOVERY_WAL_STREAM); ResetLatch(&XLogCtl->recoveryWakeupLatch); now = GetCurrentTimestamp(); } last_fail_time = now; currentSource = XLOG_FROM_ARCHIVE; break; default: elog(ERROR, "unexpected WAL source %d", currentSource); } } else if (currentSource == XLOG_FROM_PG_WAL) { /* * We just successfully read a file in pg_wal. We prefer files in * the archive over ones in pg_wal, so try the next file again * from the archive first. */ if (InArchiveRecovery) currentSource = XLOG_FROM_ARCHIVE; } if (currentSource != oldSource) elog(DEBUG2, "switched WAL source from %s to %s after %s", xlogSourceNames[oldSource], xlogSourceNames[currentSource], lastSourceFailed ? "failure" : "success"); /* * We've now handled possible failure. Try to read from the chosen * source. */ lastSourceFailed = false; switch (currentSource) { case XLOG_FROM_ARCHIVE: case XLOG_FROM_PG_WAL: /* Close any old file we might have open. */ if (readFile >= 0) { close(readFile); readFile = -1; } /* Reset curFileTLI if random fetch. */ if (randAccess) curFileTLI = 0; /* * Try to restore the file from archive, or read an existing * file from pg_wal. */ readFile = XLogFileReadAnyTLI(readSegNo, DEBUG2, currentSource == XLOG_FROM_ARCHIVE ? XLOG_FROM_ANY : currentSource); if (readFile >= 0) return true; /* success! */ /* * Nope, not found in archive or pg_wal. */ lastSourceFailed = true; break; case XLOG_FROM_STREAM: { bool havedata; /* * We should be able to move to XLOG_FROM_STREAM * only in standby mode. */ Assert(StandbyMode); /* * Check if WAL receiver is still active. */ if (!WalRcvStreaming()) { lastSourceFailed = true; break; } /* * Walreceiver is active, so see if new data has arrived. * * We only advance XLogReceiptTime when we obtain fresh * WAL from walreceiver and observe that we had already * processed everything before the most recent "chunk" * that it flushed to disk. In steady state where we are * keeping up with the incoming data, XLogReceiptTime will * be updated on each cycle. When we are behind, * XLogReceiptTime will not advance, so the grace time * allotted to conflicting queries will decrease. */ if (RecPtr < receivedUpto) havedata = true; else { XLogRecPtr latestChunkStart; receivedUpto = GetWalRcvWriteRecPtr(&latestChunkStart, &receiveTLI); if (RecPtr < receivedUpto && receiveTLI == curFileTLI) { havedata = true; if (latestChunkStart <= RecPtr) { XLogReceiptTime = GetCurrentTimestamp(); SetCurrentChunkStartTime(XLogReceiptTime); } } else havedata = false; } if (havedata) { /* * Great, streamed far enough. Open the file if it's * not open already. Also read the timeline history * file if we haven't initialized timeline history * yet; it should be streamed over and present in * pg_wal by now. Use XLOG_FROM_STREAM so that source * info is set correctly and XLogReceiptTime isn't * changed. */ if (readFile < 0) { if (!expectedTLEs) expectedTLEs = readTimeLineHistory(receiveTLI); readFile = XLogFileRead(readSegNo, PANIC, receiveTLI, XLOG_FROM_STREAM, false); Assert(readFile >= 0); } else { /* just make sure source info is correct... */ readSource = XLOG_FROM_STREAM; XLogReceiptSource = XLOG_FROM_STREAM; return true; } break; } /* * Data not here yet. Check for trigger, then wait for * walreceiver to wake us up when new WAL arrives. */ if (CheckForStandbyTrigger()) { /* * Note that we don't "return false" immediately here. * After being triggered, we still want to replay all * the WAL that was already streamed. It's in pg_wal * now, so we just treat this as a failure, and the * state machine will move on to replay the streamed * WAL from pg_wal, and then recheck the trigger and * exit replay. */ lastSourceFailed = true; break; } /* * Since we have replayed everything we have received so * far and are about to start waiting for more WAL, let's * tell the upstream server our replay location now so * that pg_stat_replication doesn't show stale * information. */ if (!streaming_reply_sent) { WalRcvForceReply(); streaming_reply_sent = true; } /* * Wait for more WAL to arrive. Time out after 5 seconds * to react to a trigger file promptly and to check if the * WAL receiver is still active. */ (void) WaitLatch(&XLogCtl->recoveryWakeupLatch, WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH, 5000L, WAIT_EVENT_RECOVERY_WAL_ALL); ResetLatch(&XLogCtl->recoveryWakeupLatch); break; } default: elog(ERROR, "unexpected WAL source %d", currentSource); } /* * This possibly-long loop needs to handle interrupts of startup * process. */ HandleStartupProcInterrupts(); } return false; /* not reached */ } /* * Determine what log level should be used to report a corrupt WAL record * in the current WAL page, previously read by XLogPageRead(). * * 'emode' is the error mode that would be used to report a file-not-found * or legitimate end-of-WAL situation. Generally, we use it as-is, but if * we're retrying the exact same record that we've tried previously, only * complain the first time to keep the noise down. However, we only do when * reading from pg_wal, because we don't expect any invalid records in archive * or in records streamed from master. Files in the archive should be complete, * and we should never hit the end of WAL because we stop and wait for more WAL * to arrive before replaying it. * * NOTE: This function remembers the RecPtr value it was last called with, * to suppress repeated messages about the same record. Only call this when * you are about to ereport(), or you might cause a later message to be * erroneously suppressed. */ static int emode_for_corrupt_record(int emode, XLogRecPtr RecPtr) { static XLogRecPtr lastComplaint = 0; if (readSource == XLOG_FROM_PG_WAL && emode == LOG) { if (RecPtr == lastComplaint) emode = DEBUG1; else lastComplaint = RecPtr; } return emode; } /* * Check to see whether the user-specified trigger file exists and whether a * promote request has arrived. If either condition holds, return true. */ static bool CheckForStandbyTrigger(void) { struct stat stat_buf; static bool triggered = false; if (triggered) return true; if (IsPromoteTriggered()) { /* * In 9.1 and 9.2 the postmaster unlinked the promote file inside the * signal handler. It now leaves the file in place and lets the * Startup process do the unlink. This allows Startup to know whether * it should create a full checkpoint before starting up (fallback * mode). Fast promotion takes precedence. */ if (stat(PROMOTE_SIGNAL_FILE, &stat_buf) == 0) { unlink(PROMOTE_SIGNAL_FILE); unlink(FALLBACK_PROMOTE_SIGNAL_FILE); fast_promote = true; } else if (stat(FALLBACK_PROMOTE_SIGNAL_FILE, &stat_buf) == 0) { unlink(FALLBACK_PROMOTE_SIGNAL_FILE); fast_promote = false; } ereport(LOG, (errmsg("received promote request"))); ResetPromoteTriggered(); triggered = true; return true; } if (PromoteTriggerFile == NULL || strcmp(PromoteTriggerFile, "") == 0) return false; if (stat(PromoteTriggerFile, &stat_buf) == 0) { ereport(LOG, (errmsg("promote trigger file found: %s", PromoteTriggerFile))); unlink(PromoteTriggerFile); triggered = true; fast_promote = true; return true; } else if (errno != ENOENT) ereport(ERROR, (errcode_for_file_access(), errmsg("could not stat promote trigger file \"%s\": %m", PromoteTriggerFile))); return false; } /* * Remove the files signaling a standby promotion request. */ void RemovePromoteSignalFiles(void) { unlink(PROMOTE_SIGNAL_FILE); unlink(FALLBACK_PROMOTE_SIGNAL_FILE); } /* * Check to see if a promote request has arrived. Should be * called by postmaster after receiving SIGUSR1. */ bool CheckPromoteSignal(void) { struct stat stat_buf; if (stat(PROMOTE_SIGNAL_FILE, &stat_buf) == 0 || stat(FALLBACK_PROMOTE_SIGNAL_FILE, &stat_buf) == 0) return true; return false; } /* * Wake up startup process to replay newly arrived WAL, or to notice that * failover has been requested. */ void WakeupRecovery(void) { SetLatch(&XLogCtl->recoveryWakeupLatch); } /* * Update the WalWriterSleeping flag. */ void SetWalWriterSleeping(bool sleeping) { SpinLockAcquire(&XLogCtl->info_lck); XLogCtl->WalWriterSleeping = sleeping; SpinLockRelease(&XLogCtl->info_lck); } /* * Schedule a walreceiver wakeup in the main recovery loop. */ void XLogRequestWalReceiverReply(void) { doRequestWalReceiverReply = true; }