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Make pg_ctl stop/restart/promote recheck postmaster aliveness.
"pg_ctl stop/restart" checked that the postmaster PID is valid just once, as a side-effect of sending the stop signal, and then would wait-till-timeout for the postmaster.pid file to go away. This neglects the case wherein the postmaster dies uncleanly after we signal it. Similarly, once "pg_ctl promote" has sent the signal, it'd wait for the corresponding on-disk state change to occur even if the postmaster dies. I'm not sure how we've managed not to notice this problem, but it seems to explain slow execution of the 017_shm.pl test script on AIX since commit 4fdbf9a, which added a speculative "pg_ctl stop" with the idea of making real sure that the postmaster isn't there. In the test steps that kill-9 and then restart the postmaster, it's possible to get past the initial signal attempt before kill() stops working for the doomed postmaster. If that happens, pg_ctl waited till PGCTLTIMEOUT before giving up ... and the buildfarm's AIX members have that set very high. To fix, include a "kill(pid, 0)" test (similar to what postmaster_is_alive uses) in these wait loops, so that we'll give 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 the wait-for-stop loop, and it seems desirable to put a similar function beside that for wait-for-promote. Back-patch to all supported versions, since pg_ctl's wait logic is substantially identical in all, and we're seeing the slow test behavior in all branches. Discussion: https://postgr.es/m/20220210023537.GA3222837@rfd.leadboat.com
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‎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
static pgpid_t start_postmaster(void);
156156
static void read_post_opts(void);
157157

158-
static WaitPMResult wait_for_postmaster(pgpid_t pm_pid, bool do_checkpoint);
158+
static WaitPMResult wait_for_postmaster_start(pgpid_t pm_pid, bool do_checkpoint);
159+
static bool wait_for_postmaster_stop(void);
160+
static bool wait_for_postmaster_promote(void);
159161
static bool postmaster_is_alive(pid_t pid);
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
static WaitPMResult
593-
wait_for_postmaster(pgpid_t pm_pid, bool do_checkpoint)
595+
wait_for_postmaster_start(pgpid_t pm_pid, bool do_checkpoint)
594596
{
595597
int i;
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+
static bool
712+
wait_for_postmaster_stop(void)
713+
{
714+
int cnt;
715+
716+
for (cnt = 0; cnt < wait_seconds * WAITS_PER_SEC; cnt++)
717+
{
718+
pgpid_t pid;
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+
static bool
749+
wait_for_postmaster_promote(void)
750+
{
751+
int cnt;
752+
753+
for (cnt = 0; cnt < wait_seconds * WAITS_PER_SEC; cnt++)
754+
{
755+
pgpid_t pid;
756+
DBState state;
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
static void
705777
unlimit_core_size(void)
@@ -914,7 +986,7 @@ do_start(void)
914986

915987
print_msg(_("waiting for server to start..."));
916988

917-
switch (wait_for_postmaster(pm_pid, false))
989+
switch (wait_for_postmaster_start(pm_pid, false))
918990
{
919991
case POSTMASTER_READY:
920992
print_msg(_(" done\n"));
@@ -949,7 +1021,6 @@ do_start(void)
9491021
static void
9501022
do_stop(void)
9511023
{
952-
int cnt;
9531024
pgpid_t pid;
9541025
struct stat statbuf;
9551026

@@ -1000,19 +1071,7 @@ do_stop(void)
10001071

10011072
print_msg(_("waiting for server to shut down..."));
10021073

1003-
for (cnt = 0; cnt < wait_seconds * WAITS_PER_SEC; cnt++)
1004-
{
1005-
if ((pid = get_pgpid(false)) != 0)
1006-
{
1007-
if (cnt % WAITS_PER_SEC == 0)
1008-
print_msg(".");
1009-
pg_usleep(USEC_PER_SEC / WAITS_PER_SEC);
1010-
}
1011-
else
1012-
break;
1013-
}
1014-
1015-
if (pid != 0) /* pid file still exists */
1074+
if (!wait_for_postmaster_stop())
10161075
{
10171076
print_msg(_(" failed\n"));
10181077

@@ -1036,7 +1095,6 @@ do_stop(void)
10361095
static void
10371096
do_restart(void)
10381097
{
1039-
int cnt;
10401098
pgpid_t pid;
10411099
struct stat statbuf;
10421100

@@ -1090,20 +1148,7 @@ do_restart(void)
10901148
print_msg(_("waiting for server to shut down..."));
10911149

10921150
/* always wait for restart */
1093-
1094-
for (cnt = 0; cnt < wait_seconds * WAITS_PER_SEC; cnt++)
1095-
{
1096-
if ((pid = get_pgpid(false)) != 0)
1097-
{
1098-
if (cnt % WAITS_PER_SEC == 0)
1099-
print_msg(".");
1100-
pg_usleep(USEC_PER_SEC / WAITS_PER_SEC);
1101-
}
1102-
else
1103-
break;
1104-
}
1105-
1106-
if (pid != 0) /* pid file still exists */
1151+
if (!wait_for_postmaster_stop())
11071152
{
11081153
print_msg(_(" failed\n"));
11091154

@@ -1228,21 +1273,8 @@ do_promote(void)
12281273

12291274
if (do_wait)
12301275
{
1231-
DBState state = DB_STARTUP;
1232-
int cnt;
1233-
12341276
print_msg(_("waiting for server to promote..."));
1235-
for (cnt = 0; cnt < wait_seconds * WAITS_PER_SEC; cnt++)
1236-
{
1237-
state = get_control_dbstate();
1238-
if (state == DB_IN_PRODUCTION)
1239-
break;
1240-
1241-
if (cnt % WAITS_PER_SEC == 0)
1242-
print_msg(".");
1243-
pg_usleep(USEC_PER_SEC / WAITS_PER_SEC);
1244-
}
1245-
if (state == DB_IN_PRODUCTION)
1277+
if (wait_for_postmaster_promote())
12461278
{
12471279
print_msg(_(" done\n"));
12481280
print_msg(_("server promoted\n"));
@@ -1661,7 +1693,7 @@ pgwin32_ServiceMain(DWORD argc, LPTSTR *argv)
16611693
if (do_wait)
16621694
{
16631695
write_eventlog(EVENTLOG_INFORMATION_TYPE, _("Waiting for server startup...\n"));
1664-
if (wait_for_postmaster(postmasterPID, true) != POSTMASTER_READY)
1696+
if (wait_for_postmaster_start(postmasterPID, true) != POSTMASTER_READY)
16651697
{
16661698
write_eventlog(EVENTLOG_ERROR_TYPE, _("Timed out waiting for server startup\n"));
16671699
pgwin32_SetServiceStatus(SERVICE_STOPPED);
@@ -1682,7 +1714,7 @@ pgwin32_ServiceMain(DWORD argc, LPTSTR *argv)
16821714
{
16831715
/*
16841716
* status.dwCheckPoint can be incremented by
1685-
* wait_for_postmaster(), so it might not start from 0.
1717+
* wait_for_postmaster_start(), so it might not start from 0.
16861718
*/
16871719
int maxShutdownCheckPoint = status.dwCheckPoint + 12;
16881720

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