Horton

Re: Race conditions in 019_replslot_limit.pl

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Masahiko Sawada <sawada.mshk@gmail.com>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>, hlinnaka@iki.fi, pgsql-hackers@postgresql.org
Date: 2022-02-18T05:55:21Z
Lists: pgsql-hackers 
Hi,

On 2022-02-17 19:41:40 -0800, Andres Freund wrote:
> At this point the psql "walsender" is *not* terminated, because the fatal
> message is waiting behind all the WAL data sent. Which also means that the
> slot isn't yet released.

Isn't it pretty bonkers that we allow error processing to get stuck behind
network traffic, *before* we have have released resources (locks etc)?

I wonder if we should try to send, but do it in a nonblocking way.

Greetings,

Andres Freund

Commits

  1. Revert 019_replslot_limit.pl related debugging aids.

  2. Don't fail for > 1 walsenders in 019_replslot_limit, add debug messages.

  3. Add retries for further investigation of 019_replslot_limit.pl failures.

  4. Add further debug info to help debug 019_replslot_limit.pl failures.

  5. Add temporary debug info to help debug 019_replslot_limit.pl failures.

  6. Move replication slot release to before_shmem_exit().

  7. Server-side fix for delayed NOTIFY and SIGTERM processing.