Horton

Re: pg_rewind WAL segments deletion pitfall

torikoshia <torikoshia@oss.nttdata.com>

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From: torikoshia <torikoshia@oss.nttdata.com>
To: Polina Bungina <bungina@gmail.com>
Cc: Kyotaro Horiguchi <horikyota.ntt@gmail.com>, cyberdemn@gmail.com, pgsql-hackers@lists.postgresql.org
Date: 2023-06-28T13:28:13Z
Lists: pgsql-bugs, pgsql-hackers

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On 2022-09-29 17:18, Polina Bungina wrote:
> I agree with your suggestions, so here is the updated version of
> patch. Hope I haven't missed anything.
> 
> Regards,
> Polina Bungina

Thanks for working on this!
It seems like we are also facing the same issue.

I tested the v3 patch under our condition, old primary has succeeded to 
become new standby.


BTW when I used pg_rewind-removes-wal-segments-reproduce.sh attached in 
[1], old primary also failed to become standby:

   FATAL:  could not receive data from WAL stream: ERROR:  requested WAL 
segment 000000020000000000000007 has already been removed

However, I think this is not a problem:  just adding restore_command 
like below fixed the situation.

   echo "restore_command = '/bin/cp `pwd`/newarch/%f %p'" >> 
oldprim/postgresql.conf

Attached modified reproduction script for reference.

[1]https://www.postgresql.org/message-id/CAFh8B%3DnNiFZOAPsv49gffxHBPzwmZ%3D6Msd4miMis87K%3Dd9rcRA%40mail.gmail.com


-- 
Regards,

--
Atsushi Torikoshi
NTT DATA CORPORATION

Commits

  1. Fix newly introduced 010_keep_recycled_wals.pl

  2. Avoid deleting critical WAL segments during pg_rewind