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Commit496ee64

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Prefer standby promotion over recovery pause.
Previously if a promotion was triggered while recovery was paused,the paused state continued. Also recovery could be paused by executingpg_wal_replay_pause() even while a promotion was ongoing. That is,recovery pause had higher priority over a standby promotion.But this behavior was not desirable because most users basically wantedthe recovery to complete as soon as possible and the server to becomethe master when they requested a promotion.This commit changes recovery so that it prefers a promotion overrecovery pause. That is, if a promotion is triggered while recoveryis paused, the paused state ends and a promotion continues. Alsothis commit makes recovery pause functions like pg_wal_replay_pause()throw an error if they are executed while a promotion is ongoing.Internally, this commit adds new internal function PromoteIsTriggered()that returns true if a promotion is triggered. Since the name ofthis function and the existing function IsPromoteTriggered() areconfusingly similar, the commit changes the name of IsPromoteTriggered()to IsPromoteSignaled, as more appropriate name.Author: Fujii MasaoReviewed-by: Atsushi Torikoshi, Sergei KornilovDiscussion:https://postgr.es/m/00c194b2-dbbb-2e8a-5b39-13f14048ef0a@oss.nttdata.com
1 parente09ad07 commit496ee64

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7 files changed

+93
-15
lines changed

7 files changed

+93
-15
lines changed

‎doc/src/sgml/config.sgml

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -3590,6 +3590,9 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"' # Windows
35903590
This setting has no effect if no recovery target is set.
35913591
If <xref linkend="guc-hot-standby"/> is not enabled, a setting of
35923592
<literal>pause</literal> will act the same as <literal>shutdown</literal>.
3593+
If the recovery target is reached while a promotion is ongoing,
3594+
a setting of <literal>pause</literal> will act the same as
3595+
<literal>promote</literal>.
35933596
</para>
35943597
<para>
35953598
In any case, if a recovery target is configured but the archive

‎doc/src/sgml/func.sgml

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -20177,6 +20177,13 @@ postgres=# SELECT * FROM pg_walfile_name_offset(pg_stop_backup());
2017720177
recovery is resumed.
2017820178
</para>
2017920179

20180+
<para>
20181+
<function>pg_wal_replay_pause</function> and
20182+
<function>pg_wal_replay_resume</function> cannot be executed while
20183+
a promotion is ongoing. If a promotion is triggered while recovery
20184+
is paused, the paused state ends and a promotion continues.
20185+
</para>
20186+
2018020187
<para>
2018120188
If streaming replication is disabled, the paused state may continue
2018220189
indefinitely without problem. While streaming replication is in

‎src/backend/access/transam/xlog.c

Lines changed: 60 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -229,6 +229,12 @@ static bool LocalRecoveryInProgress = true;
229229
*/
230230
staticboolLocalHotStandbyActive= false;
231231

232+
/*
233+
* Local copy of SharedPromoteIsTriggered variable. False actually means "not
234+
* known, need to check the shared state".
235+
*/
236+
staticboolLocalPromoteIsTriggered= false;
237+
232238
/*
233239
* Local state for XLogInsertAllowed():
234240
*1: unconditionally allowed to insert XLOG
@@ -654,6 +660,12 @@ typedef struct XLogCtlData
654660
*/
655661
boolSharedHotStandbyActive;
656662

663+
/*
664+
* SharedPromoteIsTriggered indicates if a standby promotion has been
665+
* triggered. Protected by info_lck.
666+
*/
667+
boolSharedPromoteIsTriggered;
668+
657669
/*
658670
* WalWriterSleeping indicates whether the WAL writer is currently in
659671
* low-power mode (and hence should be nudged if an async commit occurs).
@@ -912,6 +924,7 @@ static void InitControlFile(uint64 sysidentifier);
912924
staticvoidWriteControlFile(void);
913925
staticvoidReadControlFile(void);
914926
staticchar*str_time(pg_time_ttnow);
927+
staticvoidSetPromoteIsTriggered(void);
915928
staticboolCheckForStandbyTrigger(void);
916929

917930
#ifdefWAL_DEBUG
@@ -5112,6 +5125,7 @@ XLOGShmemInit(void)
51125125
XLogCtl->XLogCacheBlck=XLOGbuffers-1;
51135126
XLogCtl->SharedRecoveryInProgress= true;
51145127
XLogCtl->SharedHotStandbyActive= false;
5128+
XLogCtl->SharedPromoteIsTriggered= false;
51155129
XLogCtl->WalWriterSleeping= false;
51165130

51175131
SpinLockInit(&XLogCtl->Insert.insertpos_lck);
@@ -5940,16 +5954,22 @@ recoveryPausesHere(void)
59405954
if (!LocalHotStandbyActive)
59415955
return;
59425956

5957+
/* Don't pause after standby promotion has been triggered */
5958+
if (LocalPromoteIsTriggered)
5959+
return;
5960+
59435961
ereport(LOG,
59445962
(errmsg("recovery has paused"),
59455963
errhint("Execute pg_wal_replay_resume() to continue.")));
59465964

59475965
while (RecoveryIsPaused())
59485966
{
5967+
HandleStartupProcInterrupts();
5968+
if (CheckForStandbyTrigger())
5969+
return;
59495970
pgstat_report_wait_start(WAIT_EVENT_RECOVERY_PAUSE);
59505971
pg_usleep(1000000L);/* 1000 ms */
59515972
pgstat_report_wait_end();
5952-
HandleStartupProcInterrupts();
59535973
}
59545974
}
59555975

@@ -12277,6 +12297,40 @@ emode_for_corrupt_record(int emode, XLogRecPtr RecPtr)
1227712297
returnemode;
1227812298
}
1227912299

12300+
/*
12301+
* Has a standby promotion already been triggered?
12302+
*
12303+
* Unlike CheckForStandbyTrigger(), this works in any process
12304+
* that's connected to shared memory.
12305+
*/
12306+
bool
12307+
PromoteIsTriggered(void)
12308+
{
12309+
/*
12310+
* We check shared state each time only until a standby promotion is
12311+
* triggered. We can't trigger a promotion again, so there's no need to
12312+
* keep checking after the shared variable has once been seen true.
12313+
*/
12314+
if (LocalPromoteIsTriggered)
12315+
return true;
12316+
12317+
SpinLockAcquire(&XLogCtl->info_lck);
12318+
LocalPromoteIsTriggered=XLogCtl->SharedPromoteIsTriggered;
12319+
SpinLockRelease(&XLogCtl->info_lck);
12320+
12321+
returnLocalPromoteIsTriggered;
12322+
}
12323+
12324+
staticvoid
12325+
SetPromoteIsTriggered(void)
12326+
{
12327+
SpinLockAcquire(&XLogCtl->info_lck);
12328+
XLogCtl->SharedPromoteIsTriggered= true;
12329+
SpinLockRelease(&XLogCtl->info_lck);
12330+
12331+
LocalPromoteIsTriggered= true;
12332+
}
12333+
1228012334
/*
1228112335
* Check to see whether the user-specified trigger file exists and whether a
1228212336
* promote request has arrived. If either condition holds, return true.
@@ -12285,12 +12339,11 @@ static bool
1228512339
CheckForStandbyTrigger(void)
1228612340
{
1228712341
structstatstat_buf;
12288-
staticbooltriggered= false;
1228912342

12290-
if (triggered)
12343+
if (LocalPromoteIsTriggered)
1229112344
return true;
1229212345

12293-
if (IsPromoteTriggered())
12346+
if (IsPromoteSignaled())
1229412347
{
1229512348
/*
1229612349
* In 9.1 and 9.2 the postmaster unlinked the promote file inside the
@@ -12313,8 +12366,8 @@ CheckForStandbyTrigger(void)
1231312366

1231412367
ereport(LOG, (errmsg("received promote request")));
1231512368

12316-
ResetPromoteTriggered();
12317-
triggered= true;
12369+
ResetPromoteSignaled();
12370+
SetPromoteIsTriggered();
1231812371
return true;
1231912372
}
1232012373

@@ -12326,7 +12379,7 @@ CheckForStandbyTrigger(void)
1232612379
ereport(LOG,
1232712380
(errmsg("promote trigger file found: %s",PromoteTriggerFile)));
1232812381
unlink(PromoteTriggerFile);
12329-
triggered= true;
12382+
SetPromoteIsTriggered();
1233012383
fast_promote= true;
1233112384
return true;
1233212385
}

‎src/backend/access/transam/xlogfuncs.c

Lines changed: 14 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -531,6 +531,13 @@ pg_wal_replay_pause(PG_FUNCTION_ARGS)
531531
errmsg("recovery is not in progress"),
532532
errhint("Recovery control functions can only be executed during recovery.")));
533533

534+
if (PromoteIsTriggered())
535+
ereport(ERROR,
536+
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
537+
errmsg("standby promotion is ongoing"),
538+
errhint("%s cannot be executed after promotion is triggered.",
539+
"pg_wal_replay_pause()")));
540+
534541
SetRecoveryPause(true);
535542

536543
PG_RETURN_VOID();
@@ -551,6 +558,13 @@ pg_wal_replay_resume(PG_FUNCTION_ARGS)
551558
errmsg("recovery is not in progress"),
552559
errhint("Recovery control functions can only be executed during recovery.")));
553560

561+
if (PromoteIsTriggered())
562+
ereport(ERROR,
563+
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
564+
errmsg("standby promotion is ongoing"),
565+
errhint("%s cannot be executed after promotion is triggered.",
566+
"pg_wal_replay_resume()")));
567+
554568
SetRecoveryPause(false);
555569

556570
PG_RETURN_VOID();

‎src/backend/postmaster/startup.c

Lines changed: 6 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -39,7 +39,7 @@
3939
*/
4040
staticvolatilesig_atomic_tgot_SIGHUP= false;
4141
staticvolatilesig_atomic_tshutdown_requested= false;
42-
staticvolatilesig_atomic_tpromote_triggered= false;
42+
staticvolatilesig_atomic_tpromote_signaled= false;
4343

4444
/*
4545
* Flag set when executing a restore command, to tell SIGTERM signal handler
@@ -63,7 +63,7 @@ StartupProcTriggerHandler(SIGNAL_ARGS)
6363
{
6464
intsave_errno=errno;
6565

66-
promote_triggered= true;
66+
promote_signaled= true;
6767
WakeupRecovery();
6868

6969
errno=save_errno;
@@ -197,13 +197,13 @@ PostRestoreCommand(void)
197197
}
198198

199199
bool
200-
IsPromoteTriggered(void)
200+
IsPromoteSignaled(void)
201201
{
202-
returnpromote_triggered;
202+
returnpromote_signaled;
203203
}
204204

205205
void
206-
ResetPromoteTriggered(void)
206+
ResetPromoteSignaled(void)
207207
{
208-
promote_triggered= false;
208+
promote_signaled= false;
209209
}

‎src/include/access/xlog.h

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -313,6 +313,7 @@ extern XLogRecPtr GetFlushRecPtr(void);
313313
externXLogRecPtrGetLastImportantRecPtr(void);
314314
externvoidRemovePromoteSignalFiles(void);
315315

316+
externboolPromoteIsTriggered(void);
316317
externboolCheckPromoteSignal(void);
317318
externvoidWakeupRecovery(void);
318319
externvoidSetWalWriterSleeping(boolsleeping);

‎src/include/postmaster/startup.h

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -16,7 +16,7 @@ extern void HandleStartupProcInterrupts(void);
1616
externvoidStartupProcessMain(void)pg_attribute_noreturn();
1717
externvoidPreRestoreCommand(void);
1818
externvoidPostRestoreCommand(void);
19-
externboolIsPromoteTriggered(void);
20-
externvoidResetPromoteTriggered(void);
19+
externboolIsPromoteSignaled(void);
20+
externvoidResetPromoteSignaled(void);
2121

2222
#endif/* _STARTUP_H */

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