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From: Jakub Wartak <jakub.wartak@enterprisedb.com>
Date: Mon, 6 Jul 2026 14:42:10 +0200
Message-ID: 
 <CAKZiRmxxD5y2hArj3p4Ueq2jvQoTUsUr7tjeK44OnSqxAD1ZmA@mail.gmail.com>
Subject: Re: hang during shutdown
To: Anthonin Bonnefoy <anthonin.bonnefoy@datadoghq.com>
Cc: Srinath Reddy Sadipiralla <srinath2133@gmail.com>,
 Jeremy Schneider <schneider@ardentperf.com>,
	PostgreSQL mailing lists <pgsql-hackers@postgresql.org>
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On Mon, Jul 6, 2026 at 8:30=E2=80=AFAM Anthonin Bonnefoy
<anthonin.bonnefoy@datadoghq.com> wrote:
>
> Hi,
>
> On Sun, Jul 5, 2026 at 11:55=E2=80=AFPM Jeremy Schneider
> <schneider@ardentperf.com> wrote:
> > so far, it all started with this postgres hang during a shutdown. we di=
dnt capture enough diagnostics to root-cause the domino before the hang, bu=
t the data i do have about this postgres hang is very peculiar. i'm working=
 on some automation to gather more diagnostics if there is a recurrence. in=
 the meantime i wanted to share what i do know, in case anyone else has see=
n something similar.
> >
> > postgres version 16.13
> > Ubuntu 22.04.5 LTS
> > kernel 5.15.0-1110-azure
> >
> > between log messages and wal contents, it appears PostmasterStateMachin=
e transitioned into PM_WAIT_BACKENDS but never progressed beyond this for a=
 full 30 minutes until external automation finally killed the processes.
>
> Did you have an active logical replication stream at the time of the
> shutdown? If so, it's very likely due to a bug in the logical
> walsender[..]

Aren't walsenders in general problematic for shutdowns? (not just logical, =
of
course it might be this). The PG 19 is going to have
wal_sender_shutdown_timeout, and from description it seems to match [0] to
something like that. 'netstat -ntpo' would help to see from such hanged
system (if walsenders running there at this point at all).

-J.

[0] - https://git.postgresql.org/gitweb/?p=3Dpostgresql.git;a=3Dcommitdiff;=
h=3Da8f45dee91768cf1447ffaf2527e499e75a194c3