| From: | Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> |
|---|---|
| To: | Michael Paquier <michael(dot)paquier(at)gmail(dot)com> |
| Cc: | Petr Jelinek <petr(dot)jelinek(at)2ndquadrant(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: logical replication and PANIC during shutdown checkpoint in publisher |
| Date: | 2017-05-02 15:25:44 |
| Message-ID: | 9386789a-a892-dd8c-d785-3e829a189aae@2ndquadrant.com |
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| Lists: | pgsql-hackers |
On 5/2/17 10:08, Michael Paquier wrote:
> On Tue, May 2, 2017 at 9:30 PM, Peter Eisentraut
> <peter(dot)eisentraut(at)2ndquadrant(dot)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.
The side cases with logical decoding are also not new and would need
backpatching, AIUI.
>> 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?
That's my hope.
--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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