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Commit1e8c5cf

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Make pg_ctl stop/restart/promote recheck postmaster aliveness.
"pg_ctl stop/restart" checked that the postmaster PID is valid justonce, as a side-effect of sending the stop signal, and then wouldwait-till-timeout for the postmaster.pid file to go away. Thisneglects the case wherein the postmaster dies uncleanly after wesignal it. Similarly, once "pg_ctl promote" has sent the signal,it'd wait for the corresponding on-disk state change to occureven if the postmaster dies.I'm not sure how we've managed not to notice this problem, but itseems to explain slow execution of the 017_shm.pl test script on AIXsince commit4fdbf9a, which added a speculative "pg_ctl stop" withthe idea of making real sure that the postmaster isn't there. In thetest steps that kill-9 and then restart the postmaster, it's possibleto get past the initial signal attempt before kill() stops workingfor the doomed postmaster. If that happens, pg_ctl waited tillPGCTLTIMEOUT before giving up ... and the buildfarm's AIX membershave that set very high.To fix, include a "kill(pid, 0)" test (similar to whatpostmaster_is_alive uses) in these wait loops, so that we'llgive up immediately if the postmaster PID disappears.While here, I chose to refactor those loops out of where they were.do_stop() and do_restart() can perfectly well share one copy of thewait-for-stop loop, and it seems desirable to put a similar functionbeside that for wait-for-promote.Back-patch to all supported versions, since pg_ctl's wait logicis substantially identical in all, and we're seeing the slow testbehavior in all branches.Discussion:https://postgr.es/m/20220210023537.GA3222837@rfd.leadboat.com
1 parent92f60f5 commit1e8c5cf

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1 file changed

+80
-48
lines changed

1 file changed

+80
-48
lines changed

‎src/bin/pg_ctl/pg_ctl.c‎

Lines changed: 80 additions & 48 deletions
Original file line numberDiff line numberDiff line change
@@ -155,7 +155,9 @@ static void free_readfile(char **optlines);
155155
staticpgpid_tstart_postmaster(void);
156156
staticvoidread_post_opts(void);
157157

158-
staticWaitPMResultwait_for_postmaster(pgpid_tpm_pid,booldo_checkpoint);
158+
staticWaitPMResultwait_for_postmaster_start(pgpid_tpm_pid,booldo_checkpoint);
159+
staticboolwait_for_postmaster_stop(void);
160+
staticboolwait_for_postmaster_promote(void);
159161
staticboolpostmaster_is_alive(pid_tpid);
160162

161163
#if defined(HAVE_GETRLIMIT)&& defined(RLIMIT_CORE)
@@ -590,7 +592,7 @@ start_postmaster(void)
590592
* manager checkpoint, it's got nothing to do with database checkpoints!!
591593
*/
592594
staticWaitPMResult
593-
wait_for_postmaster(pgpid_tpm_pid,booldo_checkpoint)
595+
wait_for_postmaster_start(pgpid_tpm_pid,booldo_checkpoint)
594596
{
595597
inti;
596598

@@ -700,6 +702,76 @@ wait_for_postmaster(pgpid_t pm_pid, bool do_checkpoint)
700702
}
701703

702704

705+
/*
706+
* Wait for the postmaster to stop.
707+
*
708+
* Returns true if the postmaster stopped cleanly (i.e., removed its pidfile).
709+
* Returns false if the postmaster dies uncleanly, or if we time out.
710+
*/
711+
staticbool
712+
wait_for_postmaster_stop(void)
713+
{
714+
intcnt;
715+
716+
for (cnt=0;cnt<wait_seconds*WAITS_PER_SEC;cnt++)
717+
{
718+
pgpid_tpid;
719+
720+
if ((pid=get_pgpid(false))==0)
721+
return true;/* pid file is gone */
722+
723+
if (kill((pid_t)pid,0)!=0)
724+
{
725+
/*
726+
* Postmaster seems to have died. Check the pid file once more to
727+
* avoid a race condition, but give up waiting.
728+
*/
729+
if (get_pgpid(false)==0)
730+
return true;/* pid file is gone */
731+
return false;/* postmaster died untimely */
732+
}
733+
734+
if (cnt %WAITS_PER_SEC==0)
735+
print_msg(".");
736+
pg_usleep(USEC_PER_SEC /WAITS_PER_SEC);
737+
}
738+
return false;/* timeout reached */
739+
}
740+
741+
742+
/*
743+
* Wait for the postmaster to promote.
744+
*
745+
* Returns true on success, else false.
746+
* To avoid waiting uselessly, we check for postmaster death here too.
747+
*/
748+
staticbool
749+
wait_for_postmaster_promote(void)
750+
{
751+
intcnt;
752+
753+
for (cnt=0;cnt<wait_seconds*WAITS_PER_SEC;cnt++)
754+
{
755+
pgpid_tpid;
756+
DBStatestate;
757+
758+
if ((pid=get_pgpid(false))==0)
759+
return false;/* pid file is gone */
760+
if (kill((pid_t)pid,0)!=0)
761+
return false;/* postmaster died */
762+
763+
state=get_control_dbstate();
764+
if (state==DB_IN_PRODUCTION)
765+
return true;/* successful promotion */
766+
767+
if (cnt %WAITS_PER_SEC==0)
768+
print_msg(".");
769+
pg_usleep(USEC_PER_SEC /WAITS_PER_SEC);
770+
}
771+
return false;/* timeout reached */
772+
}
773+
774+
703775
#if defined(HAVE_GETRLIMIT)&& defined(RLIMIT_CORE)
704776
staticvoid
705777
unlimit_core_size(void)
@@ -913,7 +985,7 @@ do_start(void)
913985

914986
print_msg(_("waiting for server to start..."));
915987

916-
switch (wait_for_postmaster(pm_pid, false))
988+
switch (wait_for_postmaster_start(pm_pid, false))
917989
{
918990
casePOSTMASTER_READY:
919991
print_msg(_(" done\n"));
@@ -948,7 +1020,6 @@ do_start(void)
9481020
staticvoid
9491021
do_stop(void)
9501022
{
951-
intcnt;
9521023
pgpid_tpid;
9531024
structstatstatbuf;
9541025

@@ -999,19 +1070,7 @@ do_stop(void)
9991070

10001071
print_msg(_("waiting for server to shut down..."));
10011072

1002-
for (cnt=0;cnt<wait_seconds*WAITS_PER_SEC;cnt++)
1003-
{
1004-
if ((pid=get_pgpid(false))!=0)
1005-
{
1006-
if (cnt %WAITS_PER_SEC==0)
1007-
print_msg(".");
1008-
pg_usleep(USEC_PER_SEC /WAITS_PER_SEC);
1009-
}
1010-
else
1011-
break;
1012-
}
1013-
1014-
if (pid!=0)/* pid file still exists */
1073+
if (!wait_for_postmaster_stop())
10151074
{
10161075
print_msg(_(" failed\n"));
10171076

@@ -1035,7 +1094,6 @@ do_stop(void)
10351094
staticvoid
10361095
do_restart(void)
10371096
{
1038-
intcnt;
10391097
pgpid_tpid;
10401098
structstatstatbuf;
10411099

@@ -1089,20 +1147,7 @@ do_restart(void)
10891147
print_msg(_("waiting for server to shut down..."));
10901148

10911149
/* always wait for restart */
1092-
1093-
for (cnt=0;cnt<wait_seconds*WAITS_PER_SEC;cnt++)
1094-
{
1095-
if ((pid=get_pgpid(false))!=0)
1096-
{
1097-
if (cnt %WAITS_PER_SEC==0)
1098-
print_msg(".");
1099-
pg_usleep(USEC_PER_SEC /WAITS_PER_SEC);
1100-
}
1101-
else
1102-
break;
1103-
}
1104-
1105-
if (pid!=0)/* pid file still exists */
1150+
if (!wait_for_postmaster_stop())
11061151
{
11071152
print_msg(_(" failed\n"));
11081153

@@ -1222,21 +1267,8 @@ do_promote(void)
12221267

12231268
if (do_wait)
12241269
{
1225-
DBStatestate=DB_STARTUP;
1226-
intcnt;
1227-
12281270
print_msg(_("waiting for server to promote..."));
1229-
for (cnt=0;cnt<wait_seconds*WAITS_PER_SEC;cnt++)
1230-
{
1231-
state=get_control_dbstate();
1232-
if (state==DB_IN_PRODUCTION)
1233-
break;
1234-
1235-
if (cnt %WAITS_PER_SEC==0)
1236-
print_msg(".");
1237-
pg_usleep(USEC_PER_SEC /WAITS_PER_SEC);
1238-
}
1239-
if (state==DB_IN_PRODUCTION)
1271+
if (wait_for_postmaster_promote())
12401272
{
12411273
print_msg(_(" done\n"));
12421274
print_msg(_("server promoted\n"));
@@ -1655,7 +1687,7 @@ pgwin32_ServiceMain(DWORD argc, LPTSTR *argv)
16551687
if (do_wait)
16561688
{
16571689
write_eventlog(EVENTLOG_INFORMATION_TYPE,_("Waiting for server startup...\n"));
1658-
if (wait_for_postmaster(postmasterPID, true)!=POSTMASTER_READY)
1690+
if (wait_for_postmaster_start(postmasterPID, true)!=POSTMASTER_READY)
16591691
{
16601692
write_eventlog(EVENTLOG_ERROR_TYPE,_("Timed out waiting for server startup\n"));
16611693
pgwin32_SetServiceStatus(SERVICE_STOPPED);
@@ -1676,7 +1708,7 @@ pgwin32_ServiceMain(DWORD argc, LPTSTR *argv)
16761708
{
16771709
/*
16781710
* status.dwCheckPoint can be incremented by
1679-
*wait_for_postmaster(), so it might not start from 0.
1711+
*wait_for_postmaster_start(), so it might not start from 0.
16801712
*/
16811713
intmaxShutdownCheckPoint=status.dwCheckPoint+12;
16821714

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