Add wait events for recovery conflicts.

This commit introduces new wait events RecoveryConflictSnapshot and
RecoveryConflictTablespace. The former is reported while waiting for
recovery conflict resolution on a vacuum cleanup. The latter is reported
while waiting for recovery conflict resolution on dropping tablespace.

Also this commit changes the code so that the wait event Lock is reported
while waiting in ResolveRecoveryConflictWithVirtualXIDs() for recovery
conflict resolution on a lock. Basically the wait event Lock is reported
during that wait, but previously was not reported only when that wait
happened in ResolveRecoveryConflictWithVirtualXIDs().

Author: Masahiko Sawada
Reviewed-by: Fujii Masao
Discussion: https://postgr.es/m/CA+fd4k4mXWTwfQLS3RPwGr4xnfAEs1ysFfgYHvmmoUgv6Zxvmg@mail.gmail.com

doc/src/sgml/monitoring.sgml

@@ -1346,7 +1346,7 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
          <entry>Waiting in an extension.</entry>
         </row>
         <row>
-         <entry morerows="38"><literal>IPC</literal></entry>
+         <entry morerows="40"><literal>IPC</literal></entry>
          <entry><literal>BackupWaitWalArchive</literal></entry>
          <entry>Waiting for WAL files required for the backup to be successfully archived.</entry>
         </row>
@@ -1482,6 +1482,14 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
          <entry><literal>Promote</literal></entry>
          <entry>Waiting for standby promotion.</entry>
         </row>
+        <row>
+         <entry><literal>RecoveryConflictSnapshot</literal></entry>
+         <entry>Waiting for recovery conflict resolution on a vacuum cleanup.</entry>
+        </row>
+        <row>
+         <entry><literal>RecoveryConflictTablespace</literal></entry>
+         <entry>Waiting for recovery conflict resolution on dropping tablespace.</entry>
+        </row>
         <row>
          <entry><literal>RecoveryPause</literal></entry>
          <entry>Waiting for recovery to be resumed.</entry>

src/backend/postmaster/pgstat.c

@@ -3852,6 +3852,12 @@ pgstat_get_wait_ipc(WaitEventIPC w)
 		case WAIT_EVENT_PROMOTE:
 			event_name = "Promote";
 			break;
+		case WAIT_EVENT_RECOVERY_CONFLICT_SNAPSHOT:
+			event_name = "RecoveryConflictSnapshot";
+			break;
+		case WAIT_EVENT_RECOVERY_CONFLICT_TABLESPACE:
+			event_name = "RecoveryConflictTablespace";
+			break;
 		case WAIT_EVENT_RECOVERY_PAUSE:
 			event_name = "RecoveryPause";
 			break;

src/backend/storage/ipc/standby.c

@@ -43,7 +43,9 @@ int			max_standby_streaming_delay = 30 * 1000;
 static HTAB *RecoveryLockLists;
 
 static void ResolveRecoveryConflictWithVirtualXIDs(VirtualTransactionId *waitlist,
-												   ProcSignalReason reason, bool report_waiting);
+												   ProcSignalReason reason,
+												   uint32 wait_event_info,
+												   bool report_waiting);
 static void SendRecoveryConflictWithBufferPin(ProcSignalReason reason);
 static XLogRecPtr LogCurrentRunningXacts(RunningTransactions CurrRunningXacts);
 static void LogAccessExclusiveLocks(int nlocks, xl_standby_lock *locks);
@@ -184,7 +186,7 @@ static int	standbyWait_us = STANDBY_INITIAL_WAIT_US;
  * more then we return true, if we can wait some more return false.
  */
 static bool
-WaitExceedsMaxStandbyDelay(void)
+WaitExceedsMaxStandbyDelay(uint32 wait_event_info)
 {
 	TimestampTz ltime;
 
@@ -198,7 +200,9 @@ WaitExceedsMaxStandbyDelay(void)
 	/*
 	 * Sleep a bit (this is essential to avoid busy-waiting).
 	 */
+	pgstat_report_wait_start(wait_event_info);
 	pg_usleep(standbyWait_us);
+	pgstat_report_wait_end();
 
 	/*
 	 * Progressively increase the sleep times, but not to more than 1s, since
@@ -223,7 +227,8 @@ WaitExceedsMaxStandbyDelay(void)
  */
 static void
 ResolveRecoveryConflictWithVirtualXIDs(VirtualTransactionId *waitlist,
-									   ProcSignalReason reason, bool report_waiting)
+									   ProcSignalReason reason, uint32 wait_event_info,
+									   bool report_waiting)
 {
 	TimestampTz waitStart = 0;
 	char	   *new_status;
@@ -264,7 +269,7 @@ ResolveRecoveryConflictWithVirtualXIDs(VirtualTransactionId *waitlist,
 			}
 
 			/* Is it time to kill it? */
-			if (WaitExceedsMaxStandbyDelay())
+			if (WaitExceedsMaxStandbyDelay(wait_event_info))
 			{
 				pid_t		pid;
 
@@ -317,6 +322,7 @@ ResolveRecoveryConflictWithSnapshot(TransactionId latestRemovedXid, RelFileNode
 
 	ResolveRecoveryConflictWithVirtualXIDs(backends,
 										   PROCSIG_RECOVERY_CONFLICT_SNAPSHOT,
+										   WAIT_EVENT_RECOVERY_CONFLICT_SNAPSHOT,
 										   true);
 }
 
@@ -346,6 +352,7 @@ ResolveRecoveryConflictWithTablespace(Oid tsid)
 												InvalidOid);
 	ResolveRecoveryConflictWithVirtualXIDs(temp_file_users,
 										   PROCSIG_RECOVERY_CONFLICT_TABLESPACE,
+										   WAIT_EVENT_RECOVERY_CONFLICT_TABLESPACE,
 										   true);
 }
 
@@ -417,6 +424,7 @@ ResolveRecoveryConflictWithLock(LOCKTAG locktag)
 		 */
 		ResolveRecoveryConflictWithVirtualXIDs(backends,
 											   PROCSIG_RECOVERY_CONFLICT_LOCK,
+											   PG_WAIT_LOCK | locktag.locktag_type,
 											   false);
 	}
 	else

src/include/pgstat.h

@@ -881,6 +881,8 @@ typedef enum
 	WAIT_EVENT_PARALLEL_FINISH,
 	WAIT_EVENT_PROCARRAY_GROUP_UPDATE,
 	WAIT_EVENT_PROMOTE,
+	WAIT_EVENT_RECOVERY_CONFLICT_SNAPSHOT,
+	WAIT_EVENT_RECOVERY_CONFLICT_TABLESPACE,
 	WAIT_EVENT_RECOVERY_PAUSE,
 	WAIT_EVENT_REPLICATION_ORIGIN_DROP,
 	WAIT_EVENT_REPLICATION_SLOT_DROP,