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Refactor WaitForLSNReplay() to return the result of waiting

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Currently, WaitForLSNReplay() immediately throws an error if waiting for LSN
replay is not successful.  This commit teaches  WaitForLSNReplay() to return
the result of waiting, while making pg_wal_replay_wait() responsible for
throwing an appropriate error.

This is preparation to adding 'no_error' argument to pg_wal_replay_wait() and
new function pg_wal_replay_wait_status(), which returns the last wait result
status.

Additionally, we stop distinguishing situations when we find our instance to
be not in a recovery state before entering the waiting loop and inside
the waiting loop.  Standby promotion may happen at any moment, even between
issuing a procedure call statement and pg_wal_replay_wait() doing a first
check of recovery status.  Thus, there is no pointing distinguishing these
situations.

Also, since we may exit the waiting loop and see our instance not in recovery
without throwing an error, we need to deleteLSNWaiter() in that case. We do
this unconditionally for the sake of simplicity, even if standby was already
promoted after reaching the target LSN, the startup process surely already
deleted us.

Reported-by: Michael Paquier
Discussion: https://postgr.es/m/ZtUF17gF0pNpwZDI%40paquier.xyz
Reviewed-by: Michael Paquier, Pavel Borisov
This commit is contained in:
Alexander Korotkov
2024-10-24 14:38:27 +03:00
parent 6cfebfe88b
commit 73da6b8d1b
4 changed files with 54 additions and 24 deletions
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13
src/include/access/xlogwait.h
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@ -70,12 +70,23 @@ typedef struct WaitLSNState
WaitLSNProcInfo procInfos[FLEXIBLE_ARRAY_MEMBER];
} WaitLSNState;
/*
* Result statuses for WaitForLSNReplay().
*/
typedef enum
{
WAIT_LSN_RESULT_SUCCESS, /* Target LSN is reached */
WAIT_LSN_RESULT_TIMEOUT, /* Timeout occurred */
WAIT_LSN_RESULT_NOT_IN_RECOVERY, /* Recovery ended before or during our
* wait */
} WaitLSNResult;
extern PGDLLIMPORT WaitLSNState *waitLSNState;
extern Size WaitLSNShmemSize(void);
extern void WaitLSNShmemInit(void);
extern void WaitLSNSetLatches(XLogRecPtr currentLSN);
extern void WaitLSNCleanup(void);
extern void WaitForLSNReplay(XLogRecPtr targetLSN, int64 timeout);
extern WaitLSNResult WaitForLSNReplay(XLogRecPtr targetLSN, int64 timeout);
#endif /* XLOG_WAIT_H */