Horton

Re: logical replication and PANIC during shutdown checkpoint in publisher

Michael Paquier <michael.paquier@gmail.com>

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From: Michael Paquier <michael.paquier@gmail.com>
To: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Cc: Petr Jelinek <petr.jelinek@2ndquadrant.com>, Andres Freund <andres@anarazel.de>, Fujii Masao <masao.fujii@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2017-05-02T14:08:41Z
Lists: pgsql-hackers 
On Tue, May 2, 2017 at 9:30 PM, Peter Eisentraut
<peter.eisentraut@2ndquadrant.com> wrote:
> On 5/2/17 03:11, Petr Jelinek wrote:
>> logical decoding can theoretically
>> do HOT pruning (even if the chance is really small) so it's not safe to
>> start logical replication either.
>
> This seems a bit impossible to resolve.  On the one hand, we want to
> allow streaming until after the shutdown checkpoint.  On the other hand,
> streaming itself might produce new WAL.

It would be nice to split things into two:
- patch 1 adding the signal handling that wins a backpatch.
- patch 2 fixing the side cases with logical decoding.

> Can we prevent HOT pruning during logical decoding?

It does not sound much difficult to do, couldn't you just make it a
no-op with am_walsender?
-- 
Michael

Commits

  1. Prevent possibility of panics during shutdown checkpoint.

  2. Revert "Prevent panic during shutdown checkpoint"

  3. Prevent panic during shutdown checkpoint