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: | 2017-04-25 18:17:09 |
Message-ID: | 33b68692-c2e3-09a2-6555-61e7dc7ac950@2ndquadrant.com |
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Lists: | pgsql-hackers |
On 4/21/17 00:11, Michael Paquier wrote:
> Hmm. I have been actually looking at this solution and I am having
> doubts regarding its robustness. In short this would need to be
> roughly a two-step process:
> - In PostmasterStateMachine(), SIGUSR2 is sent to the checkpoint to
> make it call ShutdownXLOG(). Prior doing that, a first signal should
> be sent to all the WAL senders with
> SignalSomeChildren(BACKEND_TYPE_WALSND). SIGUSR2 or SIGINT could be
> used.
> - At reception of this signal, all WAL senders switch to a stopping
> state, refusing commands that can generate WAL.
> - Checkpointer looks at the state of all WAL senders, looping with a
> sleep call of a couple of ms, refusing to launch the shutdown
> checkpoint as long as all WAL senders have not switched to the
> stopping state.
> - In reaper(), once checkpointer is confirmed as stopped, signal again
> the WAL senders, and tell them to perform the last loop.
Yeah that looks like a reasonable approach.
I'm not sure why in your patch you process got_SIGUSR2 in
WalSndErrorCleanup() instead of in the main loop.
--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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