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From: Petr Jelinek <petr@2ndquadrant.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Craig Ringer <craig@2ndquadrant.com>
Cc: Andres Freund <andres@2ndquadrant.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Antonin Houska <antonin.houska@gmail.com>
Cc: pgsql-hackers@postgresql.org <pgsql-hackers@postgresql.org>
Cc: Abhijit Menon-Sen <ams@2ndquadrant.com>
Subject: Re: bgworker crashed or not?
Date: Wed, 07 May 2014 02:25:40 +0200
Message-ID: <53697D84.1050103@2ndquadrant.com> (raw)
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On 06/05/14 19:05, Robert Haas wrote:
> Which brings up another point: the behavior of non-shmem-connected
> workers is totally bizarre.  An exit status other than 0 or 1 is not
> treated as a crash requiring a restart, but failure to disengage the
> deadman switch is still treated as a crash requiring a restart.  Why?
> If the workers are not shmem-connected, then no crash requires a
> system-wide restart.  Of course, there's the tiny problem that we
> aren't actually unmapping shared memory from supposedly non-shmem
> connected workers, which is a different bug, but ignoring that for the
> moment there's no reason for this logic to be like this.

Agreed.

> What I'm inclined to do is change the logic so that:
>
> (1) After a crash-and-restart sequence, zero rw->rw_crashed_at, so
> that anything which is still registered gets restarted immediately.

Yes, that's quite obvious change which I missed completely :).

> (2) If a shmem-connected backend fails to release the deadman switch
> or exits with an exit code other than 0 or 1, we crash-and-restart.  A
> non-shmem-connected backend never causes a crash-and-restart.

+1

> (3) When a background worker exits without triggering a
> crash-and-restart, an exit code of precisely 0 causes the worker to be
> unregistered; any other exit code has no special effect, so
> bgw_restart_time controls.

+1


-- 
  Petr Jelinek                  http://www.2ndQuadrant.com/
  PostgreSQL Development, 24x7 Support, Training & Services


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