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Commitd0c231d

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committed
Cosmetic adjustments for postmaster's handling of checkpointer.
Correct some comments, order some operations a bit more consistently.No functional changes.
1 parent2cfb1c6 commitd0c231d

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2 files changed

+34
-26
lines changed

2 files changed

+34
-26
lines changed

‎src/backend/postmaster/bgwriter.c

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -15,9 +15,9 @@
1515
* The bgwriter is started by the postmaster as soon as the startup subprocess
1616
* finishes, or as soon as recovery begins if we are doing archive recovery.
1717
* It remains alive until the postmaster commands it to terminate.
18-
* Normal termination is bySIGUSR2, which instructs the bgwriter to exit(0).
19-
* Emergency termination is by SIGQUIT; like any
20-
*backend, the bgwriter willsimply abort and exit on SIGQUIT.
18+
* Normal termination is bySIGTERM, which instructs the bgwriter to exit(0).
19+
* Emergency termination is by SIGQUIT; like any backend, the bgwriter will
20+
* simply abort and exit on SIGQUIT.
2121
*
2222
* If the bgwriter exits unexpectedly, the postmaster treats that the same
2323
* as a backend crash: shared memory may be corrupted, so remaining backends

‎src/backend/postmaster/postmaster.c

Lines changed: 31 additions & 23 deletions
Original file line numberDiff line numberDiff line change
@@ -239,13 +239,13 @@ static bool RecoveryError = false;/* T if WAL recovery failed */
239239
* hot standby during archive recovery.
240240
*
241241
* When the startup process is ready to start archive recovery, it signals the
242-
* postmaster, and we switch to PM_RECOVERY state. The background writeris
243-
* launched, while the startup process continues applying WAL.If Hot Standby
244-
* is enabled, then, after reaching a consistent point in WAL redo, startup
245-
* process signals us again, and we switch to PM_HOT_STANDBY state and
246-
* begin accepting connections to perform read-only queries. When archive
247-
* recovery is finished, the startup process exits with exit code 0 and we
248-
* switch to PM_RUN state.
242+
* postmaster, and we switch to PM_RECOVERY state. The background writerand
243+
*checkpointer arelaunched, while the startup process continues applying WAL.
244+
*If Hot Standbyis enabled, then, after reaching a consistent point in WAL
245+
*redo, startupprocess signals us again, and we switch to PM_HOT_STANDBY
246+
*state andbegin accepting connections to perform read-only queries. When
247+
*archiverecovery is finished, the startup process exits with exit code 0
248+
*and weswitch to PM_RUN state.
249249
*
250250
* Normal child backends can only be launched when we are in PM_RUN or
251251
* PM_HOT_STANDBY state. (We also allow launch of normal
@@ -1038,7 +1038,7 @@ PostmasterMain(int argc, char *argv[])
10381038
* handling setup of child processes. See tcop/postgres.c,
10391039
* bootstrap/bootstrap.c, postmaster/bgwriter.c, postmaster/walwriter.c,
10401040
* postmaster/autovacuum.c, postmaster/pgarch.c, postmaster/pgstat.c,
1041-
* postmaster/syslogger.c and postmaster/checkpointer.c
1041+
* postmaster/syslogger.c and postmaster/checkpointer.c.
10421042
*/
10431043
pqinitmask();
10441044
PG_SETMASK(&BlockSig);
@@ -1373,10 +1373,10 @@ ServerLoop(void)
13731373
/*
13741374
* If no background writer process is running, and we are not in a
13751375
* state that prevents it, start one. It doesn't matter if this
1376-
* fails, we'll just try again later.
1376+
* fails, we'll just try again later. Likewise for the checkpointer.
13771377
*/
13781378
if (pmState==PM_RUN||pmState==PM_RECOVERY||
1379-
pmState==PM_HOT_STANDBY)
1379+
pmState==PM_HOT_STANDBY)
13801380
{
13811381
if (BgWriterPID==0)
13821382
BgWriterPID=StartBackgroundWriter();
@@ -1386,7 +1386,8 @@ ServerLoop(void)
13861386

13871387
/*
13881388
* Likewise, if we have lost the walwriter process, try to start a new
1389-
* one.
1389+
* one. But this is needed only in normal operation (else we cannot
1390+
* be writing any new WAL).
13901391
*/
13911392
if (WalWriterPID==0&&pmState==PM_RUN)
13921393
WalWriterPID=StartWalWriter();
@@ -2131,11 +2132,12 @@ pmdie(SIGNAL_ARGS)
21312132
/* and the autovac launcher too */
21322133
if (AutoVacPID!=0)
21332134
signal_child(AutoVacPID,SIGTERM);
2135+
/* and the bgwriter too */
2136+
if (BgWriterPID!=0)
2137+
signal_child(BgWriterPID,SIGTERM);
21342138
/* and the walwriter too */
21352139
if (WalWriterPID!=0)
21362140
signal_child(WalWriterPID,SIGTERM);
2137-
if (BgWriterPID!=0)
2138-
signal_child(BgWriterPID,SIGTERM);
21392141

21402142
/*
21412143
* If we're in recovery, we can't kill the startup process
@@ -2174,13 +2176,17 @@ pmdie(SIGNAL_ARGS)
21742176

21752177
if (StartupPID!=0)
21762178
signal_child(StartupPID,SIGTERM);
2177-
if (WalReceiverPID!=0)
2178-
signal_child(WalReceiverPID,SIGTERM);
21792179
if (BgWriterPID!=0)
21802180
signal_child(BgWriterPID,SIGTERM);
2181+
if (WalReceiverPID!=0)
2182+
signal_child(WalReceiverPID,SIGTERM);
21812183
if (pmState==PM_RECOVERY)
21822184
{
2183-
/* only checkpointer is active in this state */
2185+
/*
2186+
* Only startup, bgwriter, and checkpointer should be active
2187+
* in this state; we just signaled the first two, and we don't
2188+
* want to kill checkpointer yet.
2189+
*/
21842190
pmState=PM_WAIT_BACKENDS;
21852191
}
21862192
elseif (pmState==PM_RUN||
@@ -2362,21 +2368,21 @@ reaper(SIGNAL_ARGS)
23622368
}
23632369

23642370
/*
2365-
* Crank up background tasks, if we didn't do that already
2371+
* Crank upthebackground tasks, if we didn't do that already
23662372
* when we entered consistent recovery state. It doesn't matter
23672373
* if this fails, we'll just try again later.
23682374
*/
23692375
if (BgWriterPID==0)
23702376
BgWriterPID=StartBackgroundWriter();
23712377
if (CheckpointerPID==0)
23722378
CheckpointerPID=StartCheckpointer();
2379+
if (WalWriterPID==0)
2380+
WalWriterPID=StartWalWriter();
23732381

23742382
/*
23752383
* Likewise, start other special children as needed. In a restart
23762384
* situation, some of them may be alive already.
23772385
*/
2378-
if (WalWriterPID==0)
2379-
WalWriterPID=StartWalWriter();
23802386
if (!IsBinaryUpgrade&&AutoVacuumingActive()&&AutoVacPID==0)
23812387
AutoVacPID=StartAutoVacLauncher();
23822388
if (XLogArchivingActive()&&PgArchPID==0)
@@ -2392,7 +2398,9 @@ reaper(SIGNAL_ARGS)
23922398
}
23932399

23942400
/*
2395-
* Was it the bgwriter?
2401+
* Was it the bgwriter? Normal exit can be ignored; we'll start a
2402+
* new one at the next iteration of the postmaster's main loop, if
2403+
* necessary. Any other exit condition is treated as a crash.
23962404
*/
23972405
if (pid==BgWriterPID)
23982406
{
@@ -4228,13 +4236,13 @@ sigusr1_handler(SIGNAL_ARGS)
42284236
FatalError= false;
42294237

42304238
/*
4231-
* Crank up the backgroundwriters.It doesn't matter if this fails,
4239+
* Crank up the backgroundtasks.It doesn't matter if this fails,
42324240
* we'll just try again later.
42334241
*/
4234-
Assert(CheckpointerPID==0);
4235-
CheckpointerPID=StartCheckpointer();
42364242
Assert(BgWriterPID==0);
42374243
BgWriterPID=StartBackgroundWriter();
4244+
Assert(CheckpointerPID==0);
4245+
CheckpointerPID=StartCheckpointer();
42384246

42394247
pmState=PM_RECOVERY;
42404248
}

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