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Commitd59ff6c

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Fix bug in determining when recovery has reached consistency.
When starting WAL replay from an online checkpoint, the last replayed WALrecord variable was initialized using the checkpoint record's location, eventhough the records between the REDO location and the checkpoint record hadnot been replayed yet. That was noted as "slightly confusing" but harmlessin the comment, but in some cases, it fooled CheckRecoveryConsistency toincorrectly conclude that we had already reached a consistent stateimmediately at the beginning of WAL replay. That caused the system to acceptread-only connections in hot standby mode too early, and also PANICs withmessage "WAL contains references to invalid pages".Fix by initializing the variables to the REDO location instead.In 9.2 and above, change CheckRecoveryConsistency() to uselastReplayedEndRecPtr variable when checking if backup end location hasbeen reached. It was inconsistently using EndRecPtr for that check, butlastReplayedEndRecPtr when checking min recovery point. It made nodifference before this patch, because in all the places whereCheckRecoveryConsistency was called the two variables were the same, butit was always an accident waiting to happen, and would have been wrongafter this patch anyway.Report and analysis by Tomonari Katsumata, bug #8686. Backpatch to 9.0,where hot standby was introduced.
1 parentca607b1 commitd59ff6c

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1 file changed

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  • src/backend/access/transam

1 file changed

+18
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lines changed

‎src/backend/access/transam/xlog.c

Lines changed: 18 additions & 18 deletions
Original file line numberDiff line numberDiff line change
@@ -6684,21 +6684,13 @@ StartupXLOG(void)
66846684
}
66856685

66866686
/*
6687-
* Initialize shared replayEndRecPtr, lastReplayedEndRecPtr, and
6688-
* recoveryLastXTime.
6689-
*
6690-
* This is slightly confusing if we're starting from an online
6691-
* checkpoint; we've just read and replayed the checkpoint record, but
6692-
* we're going to start replay from its redo pointer, which precedes
6693-
* the location of the checkpoint record itself. So even though the
6694-
* last record we've replayed is indeed ReadRecPtr, we haven't
6695-
* replayed all the preceding records yet. That's OK for the current
6696-
* use of these variables.
6687+
* Initialize shared variables for tracking progress of WAL replay,
6688+
* as if we had just replayed the record before the REDO location.
66976689
*/
66986690
SpinLockAcquire(&xlogctl->info_lck);
6699-
xlogctl->replayEndRecPtr=ReadRecPtr;
6691+
xlogctl->replayEndRecPtr=checkPoint.redo;
67006692
xlogctl->replayEndTLI=ThisTimeLineID;
6701-
xlogctl->lastReplayedEndRecPtr=EndRecPtr;
6693+
xlogctl->lastReplayedEndRecPtr=checkPoint.redo;
67026694
xlogctl->lastReplayedTLI=ThisTimeLineID;
67036695
xlogctl->recoveryLastXTime=0;
67046696
xlogctl->currentChunkStartTime=0;
@@ -7388,18 +7380,26 @@ StartupXLOG(void)
73887380
staticvoid
73897381
CheckRecoveryConsistency(void)
73907382
{
7383+
XLogRecPtrlastReplayedEndRecPtr;
7384+
73917385
/*
73927386
* During crash recovery, we don't reach a consistent state until we've
73937387
* replayed all the WAL.
73947388
*/
73957389
if (XLogRecPtrIsInvalid(minRecoveryPoint))
73967390
return;
73977391

7392+
/*
7393+
* assume that we are called in the startup process, and hence don't need
7394+
* a lock to read lastReplayedEndRecPtr
7395+
*/
7396+
lastReplayedEndRecPtr=XLogCtl->lastReplayedEndRecPtr;
7397+
73987398
/*
73997399
* Have we reached the point where our base backup was completed?
74007400
*/
74017401
if (!XLogRecPtrIsInvalid(ControlFile->backupEndPoint)&&
7402-
ControlFile->backupEndPoint <=EndRecPtr)
7402+
ControlFile->backupEndPoint <=lastReplayedEndRecPtr)
74037403
{
74047404
/*
74057405
* We have reached the end of base backup, as indicated by pg_control.
@@ -7412,8 +7412,8 @@ CheckRecoveryConsistency(void)
74127412

74137413
LWLockAcquire(ControlFileLock,LW_EXCLUSIVE);
74147414

7415-
if (ControlFile->minRecoveryPoint<EndRecPtr)
7416-
ControlFile->minRecoveryPoint=EndRecPtr;
7415+
if (ControlFile->minRecoveryPoint<lastReplayedEndRecPtr)
7416+
ControlFile->minRecoveryPoint=lastReplayedEndRecPtr;
74177417

74187418
ControlFile->backupStartPoint=InvalidXLogRecPtr;
74197419
ControlFile->backupEndPoint=InvalidXLogRecPtr;
@@ -7431,7 +7431,7 @@ CheckRecoveryConsistency(void)
74317431
* consistent yet.
74327432
*/
74337433
if (!reachedConsistency&& !ControlFile->backupEndRequired&&
7434-
minRecoveryPoint <=XLogCtl->lastReplayedEndRecPtr&&
7434+
minRecoveryPoint <=lastReplayedEndRecPtr&&
74357435
XLogRecPtrIsInvalid(ControlFile->backupStartPoint))
74367436
{
74377437
/*
@@ -7443,8 +7443,8 @@ CheckRecoveryConsistency(void)
74437443
reachedConsistency= true;
74447444
ereport(LOG,
74457445
(errmsg("consistent recovery state reached at %X/%X",
7446-
(uint32) (XLogCtl->lastReplayedEndRecPtr >>32),
7447-
(uint32)XLogCtl->lastReplayedEndRecPtr)));
7446+
(uint32) (lastReplayedEndRecPtr >>32),
7447+
(uint32)lastReplayedEndRecPtr)));
74487448
}
74497449

74507450
/*

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