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Kill dead-end children when there's nothing else left

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Previously, the postmaster would never try to kill dead-end child
processes, even if there were no other processes left. A dead-end
backend will eventually exit, when authentication_timeout expires, but
if a dead-end backend is the only thing that's preventing the server
from shutting down, it seems better to kill it immediately. It's
particularly important, if there was a bug in the early startup code
that prevented a dead-end child from timing out and exiting normally.

Includes a test for that case where a dead-end backend previously
prevented the server from shutting down.

Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://www.postgresql.org/message-id/a102f15f-eac4-4ff2-af02-f9ff209ec66f@iki.fi
This commit is contained in:
Heikki Linnakangas
2024-11-14 16:12:04 +02:00
parent 18d67a8d7d
commit bb861414fe
4 changed files with 116 additions and 10 deletions
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17
src/backend/postmaster/postmaster.c
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@@ -2985,10 +2985,11 @@ PostmasterStateMachine(void)
if (Shutdown >= ImmediateShutdown || FatalError)
{
/*
* Start waiting for dead_end children to die. This state
* change causes ServerLoop to stop creating new ones.
* Stop any dead_end children and stop creating new ones.
*/
pmState = PM_WAIT_DEAD_END;
ConfigurePostmasterWaitSet(false);
SignalChildren(SIGQUIT, btmask(B_DEAD_END_BACKEND));
/*
* We already SIGQUIT'd the archiver and stats processes, if
@@ -3027,9 +3028,10 @@ PostmasterStateMachine(void)
*/
FatalError = true;
pmState = PM_WAIT_DEAD_END;
ConfigurePostmasterWaitSet(false);
/* Kill the walsenders and archiver too */
SignalChildren(SIGQUIT, btmask_all_except(B_DEAD_END_BACKEND));
SignalChildren(SIGQUIT, BTYPE_MASK_ALL);
if (PgArchPID != 0)
signal_child(PgArchPID, SIGQUIT);
}
@@ -3048,14 +3050,13 @@ PostmasterStateMachine(void)
if (PgArchPID == 0 && CountChildren(btmask_all_except(B_DEAD_END_BACKEND)) == 0)
{
pmState = PM_WAIT_DEAD_END;
ConfigurePostmasterWaitSet(false);
SignalChildren(SIGTERM, BTYPE_MASK_ALL);
}
}
if (pmState == PM_WAIT_DEAD_END)
{
/* Don't allow any new socket connection events. */
ConfigurePostmasterWaitSet(false);
/*
* PM_WAIT_DEAD_END state ends when the BackendList is entirely empty
* (ie, no dead_end children remain), and the archiver is gone too.
@@ -3381,12 +3382,12 @@ SignalChildren(int signal, BackendTypeMask targetMask)
/*
* Send a termination signal to children. This considers all of our children
* processes, except syslogger and dead_end backends.
* processes, except syslogger.
*/
static void
TerminateChildren(int signal)
{
SignalChildren(signal, btmask_all_except(B_DEAD_END_BACKEND));
SignalChildren(signal, BTYPE_MASK_ALL);
if (StartupPID != 0)
{
signal_child(StartupPID, signal);