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Commit8b6b374

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Consistency check should compare last record replayed, not last record read.
EndRecPtr is the last record that we've read, but not necessarily yetreplayed. CheckRecoveryConsistency should compare minRecoveryPoint with thelast replayed record instead. This caused recovery to think it's reachedconsistency too early.Now that we do the check in CheckRecoveryConsistency correctly, we have tomove the call of that function to after redoing a record. The current place,after reading a record but before replaying it, is wrong. In particular, ifthere are no more records after the one ending at minRecoveryPoint, we don'tenter hot standby until one extra record is generated and read by thestandby, and CheckRecoveryConsistency is called. These two bugs conspiredto make the code appear to work correctly, except for the small windowbetween reading the last record that reaches minRecoveryPoint, andreplaying it.In the passing, rename recoveryLastRecPtr, which is the last recordreplayed, to lastReplayedEndRecPtr. This makes it slightly less confusingwith replayEndRecPtr, which is the last record read that we're about toreplay.Original report from Kyotaro HORIGUCHI, further diagnosis by Fujii Masao.Backpatch to 9.0, where Hot Standby subtly changed the test from"minRecoveryPoint < EndRecPtr" to "minRecoveryPoint <= EndRecPtr". Theformer works because where the test is performed, we have always read onemore record than we've replayed.
1 parent5dd1c28 commit8b6b374

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1 file changed

+19
-14
lines changed
  • src/backend/access/transam

1 file changed

+19
-14
lines changed

‎src/backend/access/transam/xlog.c

Lines changed: 19 additions & 14 deletions
Original file line numberDiff line numberDiff line change
@@ -440,10 +440,14 @@ typedef struct XLogCtlData
440440
XLogRecPtrlastCheckPointRecPtr;
441441
CheckPointlastCheckPoint;
442442

443-
/* end+1 of the last record replayed (or being replayed) */
443+
/*
444+
* lastReplayedEndRecPtr points to end+1 of the last record successfully
445+
* replayed. When we're currently replaying a record, ie. in a redo
446+
* function, replayEndRecPtr points to the end+1 of the record being
447+
* replayed, otherwise it's equal to lastReplayedEndRecPtr.
448+
*/
449+
XLogRecPtrlastReplayedEndRecPtr;
444450
XLogRecPtrreplayEndRecPtr;
445-
/* end+1 of the last record replayed */
446-
XLogRecPtrrecoveryLastRecPtr;
447451
/* timestamp of last COMMIT/ABORT record replayed (or being replayed) */
448452
TimestampTzrecoveryLastXTime;
449453
/* Are we requested to pause recovery? */
@@ -6493,7 +6497,7 @@ StartupXLOG(void)
64936497
}
64946498

64956499
/*
6496-
* Initialize shared replayEndRecPtr,recoveryLastRecPtr, and
6500+
* Initialize shared replayEndRecPtr,lastReplayedEndRecPtr, and
64976501
* recoveryLastXTime.
64986502
*
64996503
* This is slightly confusing if we're starting from an online
@@ -6506,7 +6510,7 @@ StartupXLOG(void)
65066510
*/
65076511
SpinLockAcquire(&xlogctl->info_lck);
65086512
xlogctl->replayEndRecPtr=ReadRecPtr;
6509-
xlogctl->recoveryLastRecPtr=EndRecPtr;
6513+
xlogctl->lastReplayedEndRecPtr=EndRecPtr;
65106514
xlogctl->recoveryLastXTime=0;
65116515
xlogctl->recoveryPause= false;
65126516
SpinLockRelease(&xlogctl->info_lck);
@@ -6596,9 +6600,6 @@ StartupXLOG(void)
65966600
/* Handle interrupt signals of startup process */
65976601
HandleStartupProcInterrupts();
65986602

6599-
/* Allow read-only connections if we're consistent now */
6600-
CheckRecoveryConsistency();
6601-
66026603
/*
66036604
* Pause WAL replay, if requested by a hot-standby session via
66046605
* SetRecoveryPause().
@@ -6669,16 +6670,19 @@ StartupXLOG(void)
66696670
error_context_stack=errcontext.previous;
66706671

66716672
/*
6672-
* Updateshared recoveryLastRecPtr after this record has been
6673-
* replayed.
6673+
* UpdatelastReplayedEndRecPtr after this record has been
6674+
*successfullyreplayed.
66746675
*/
66756676
SpinLockAcquire(&xlogctl->info_lck);
6676-
xlogctl->recoveryLastRecPtr=EndRecPtr;
6677+
xlogctl->lastReplayedEndRecPtr=EndRecPtr;
66776678
SpinLockRelease(&xlogctl->info_lck);
66786679

66796680
/* Remember this record as the last-applied one */
66806681
LastRec=ReadRecPtr;
66816682

6683+
/* Allow read-only connections if we're consistent now */
6684+
CheckRecoveryConsistency();
6685+
66826686
/* Exit loop if we reached inclusive recovery target */
66836687
if (!recoveryContinue)
66846688
break;
@@ -7032,13 +7036,14 @@ CheckRecoveryConsistency(void)
70327036
* Have we passed our safe starting point?
70337037
*/
70347038
if (!reachedConsistency&&
7035-
XLByteLE(minRecoveryPoint,EndRecPtr)&&
7039+
XLByteLE(minRecoveryPoint,XLogCtl->lastReplayedEndRecPtr)&&
70367040
XLogRecPtrIsInvalid(ControlFile->backupStartPoint))
70377041
{
70387042
reachedConsistency= true;
70397043
ereport(LOG,
70407044
(errmsg("consistent recovery state reached at %X/%X",
7041-
EndRecPtr.xlogid,EndRecPtr.xrecoff)));
7045+
XLogCtl->lastReplayedEndRecPtr.xlogid,
7046+
XLogCtl->lastReplayedEndRecPtr.xrecoff)));
70427047
}
70437048

70447049
/*
@@ -9676,7 +9681,7 @@ GetXLogReplayRecPtr(void)
96769681
XLogRecPtrrecptr;
96779682

96789683
SpinLockAcquire(&xlogctl->info_lck);
9679-
recptr=xlogctl->recoveryLastRecPtr;
9684+
recptr=xlogctl->lastReplayedEndRecPtr;
96809685
SpinLockRelease(&xlogctl->info_lck);
96819686

96829687
returnrecptr;

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