Zarko Aleksic <zarko.aleksic@live.com> writes:
> I'm looking for a bit of help understanding a particular behavior we are seeing with our PostgreSQL 9.6. After issuing a service shutdown command with "systemctl stop" on RHEL 7 our PostgreSQL instance started behaving weirdly. For the first time it wouldn't shutdown so easily / quickly.
> From the logs we could see that standby nodes that were trying to connect were rejected due to database being shutdown. After wal_sender_timeout and wal_receiver_timeout (default 60s) were reached the database finally shut down. It seems that walsender process was preventing the shutdown of the master database - until timeout was reached, a behavior we didn't experience before.
9.6.what?
There were several possibly-relevant bug fixes in 9.6.3 and 9.6.4,
notably this one:
Author: Tom Lane <tgl@sss.pgh.pa.us>
Branch: master Release: REL_10_BR [fca85f8ef] 2017-06-30 12:00:15 -0400
Branch: REL9_6_STABLE Release: REL9_6_4 [e9d4aa594] 2017-06-30 12:00:03 -0400
Branch: REL9_5_STABLE Release: REL9_5_8 [446914f6b] 2017-06-30 12:00:03 -0400
Branch: REL9_4_STABLE Release: REL9_4_13 [5aa8db014] 2017-06-30 12:00:03 -0400
Fix walsender to exit promptly if client requests shutdown.
It's possible for WalSndWaitForWal to be asked to wait for WAL that doesn't
exist yet. That's fine, in fact it's the normal situation if we're caught
up; but when the client requests shutdown we should not keep waiting.
The previous coding could wait indefinitely if the source server was idle.
In passing, improve the rather weak comments in this area, and slightly
rearrange some related code for better readability.
Back-patch to 9.4 where this code was introduced.
Discussion:
https://postgr.es/m/14154.1498781234@sss.pgh.pa.us I think that would only apply if the walsender's client had tried to
disconnect at the same time you were doing the master-server shutdown,
but maybe that's what happened.
There is still work going on around the walsender timeout, so maybe
what you hit is an as-yet-unresolved bug, but in any case you should
be keeping up with minor releases.
regards, tom lane