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Refine the purpose of rdb saving with accurate flags (#12925) 

In Redis, rdb is produced in three scenarios mainly.

- backup, such as `bgsave` and `save` command
- full sync in replication
- aof rewrite if `aof-use-rdb-preamble` is yes

We also have some RDB flags to identify the purpose of rdb saving.
```C
/* flags on the purpose of rdb save or load */
#define RDBFLAGS_NONE 0                 /* No special RDB loading. */
#define RDBFLAGS_AOF_PREAMBLE (1<<0)    /* Load/save the RDB as AOF preamble. */
#define RDBFLAGS_REPLICATION (1<<1)     /* Load/save for SYNC. */
```

But currently, it seems that these flags and purposes of rdb saving
don't exactly match. I find it in `rdbSaveRioWithEOFMark` which calls
`startSaving` with `RDBFLAGS_REPLICATION` but `rdbSaveRio` with
`RDBFLAGS_NONE`.
```C
int rdbSaveRioWithEOFMark(int req, rio *rdb, int *error, rdbSaveInfo *rsi) {
    char eofmark[RDB_EOF_MARK_SIZE];

    startSaving(RDBFLAGS_REPLICATION);
    getRandomHexChars(eofmark,RDB_EOF_MARK_SIZE);
    if (error) *error = 0;
    if (rioWrite(rdb,"$EOF:",5) == 0) goto werr;
    if (rioWrite(rdb,eofmark,RDB_EOF_MARK_SIZE) == 0) goto werr;
    if (rioWrite(rdb,"\r\n",2) == 0) goto werr;
    if (rdbSaveRio(req,rdb,error,RDBFLAGS_NONE,rsi) == C_ERR) goto werr;
    if (rioWrite(rdb,eofmark,RDB_EOF_MARK_SIZE) == 0) goto werr;
    stopSaving(1);
    return C_OK;

werr: /* Write error. */
    /* Set 'error' only if not already set by rdbSaveRio() call. */
    if (error && *error == 0) *error = errno;
    stopSaving(0);
    return C_ERR;
}
```

In this PR, I refine the purpose of rdb saving with accurate flags.
This commit is contained in:
Yanqi Lv 2024-02-01 19:41:02 +08:00 committed by GitHub
parent 9a7d311855
commit 62153b3b2f
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
3 changed files with 6 additions and 5 deletions
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7
src/rdb.c
View File

@ -1424,7 +1424,8 @@ werr:
return C_ERR;
}
/* This is just a wrapper to rdbSaveRio() that additionally adds a prefix
/* This helper function is only used for diskless replication.
* This is just a wrapper to rdbSaveRio() that additionally adds a prefix
* and a suffix to the generated RDB dump. The prefix is:
*
* $EOF:<40 bytes unguessable hex string>\r\n
@ -1441,7 +1442,7 @@ int rdbSaveRioWithEOFMark(int req, rio *rdb, int *error, rdbSaveInfo *rsi) {
if (rioWrite(rdb,"$EOF:",5) == 0) goto werr;
if (rioWrite(rdb,eofmark,RDB_EOF_MARK_SIZE) == 0) goto werr;
if (rioWrite(rdb,"\r\n",2) == 0) goto werr;
if (rdbSaveRio(req,rdb,error,RDBFLAGS_NONE,rsi) == C_ERR) goto werr;
if (rdbSaveRio(req,rdb,error,RDBFLAGS_REPLICATION,rsi) == C_ERR) goto werr;
if (rioWrite(rdb,eofmark,RDB_EOF_MARK_SIZE) == 0) goto werr;
stopSaving(1);
return C_OK;
@ -1528,7 +1529,7 @@ int rdbSave(int req, char *filename, rdbSaveInfo *rsi, int rdbflags) {
char tmpfile[256];
char cwd[MAXPATHLEN]; /* Current working dir path for error messages. */
startSaving(RDBFLAGS_NONE);
startSaving(rdbflags);
snprintf(tmpfile,256,"temp-%d.rdb", (int) getpid());
if (rdbSaveInternal(req,tmpfile,rsi,rdbflags) != C_OK) {

2
src/rdb.h
View File

@ -128,7 +128,7 @@
#define RDB_LOAD_SDS (1<<2)
/* flags on the purpose of rdb save or load */
#define RDBFLAGS_NONE 0 /* No special RDB loading. */
#define RDBFLAGS_NONE 0 /* No special RDB loading or saving. */
#define RDBFLAGS_AOF_PREAMBLE (1<<0) /* Load/save the RDB as AOF preamble. */
#define RDBFLAGS_REPLICATION (1<<1) /* Load/save for SYNC. */
#define RDBFLAGS_ALLOW_DUP (1<<2) /* Allow duplicated keys when loading.*/

2
src/replication.c
View File

@ -878,7 +878,7 @@ int startBgsaveForReplication(int mincapa, int req) {
retval = rdbSaveToSlavesSockets(req,rsiptr);
else {
/* Keep the page cache since it'll get used soon */
retval = rdbSaveBackground(req,server.rdb_filename,rsiptr,RDBFLAGS_KEEP_CACHE);
retval = rdbSaveBackground(req, server.rdb_filename, rsiptr, RDBFLAGS_REPLICATION | RDBFLAGS_KEEP_CACHE);
}
} else {
serverLog(LL_WARNING,"BGSAVE for replication: replication information not available, can't generate the RDB file right now. Try later.");