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Re: Sync Rep v19

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
Cc: Yeb Havinga <yebhavinga(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Sync Rep v19
Date: 2011-03-19 02:25:10
Message-ID: AANLkTimyxZJxvjS3d6T9yRj=u3k9RFO+Hzrvj207yorS@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Tue, Mar 8, 2011 at 7:05 AM, Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
> * Smart shutdown
> Smart shutdown should wait for all the waiting backends to be acked, and
> should not cause them to forcibly exit. But this leads shutdown to get stuck
> infinitely if there is no walsender at that time. To enable them to be acked
> even in that situation, we need to change postmaster so that it accepts the
> replication connection even during smart shutdown (until we reach
> PM_SHUTDOWN_2 state). Postmaster has already accepted the superuser
> connection to cancel backup during smart shutdown. So I don't think that
> the idea to accept the replication connection during smart shutdown is so
> ugly.
>
> * Fast shutdown
> I agree with you about fast shutdown. Fast shutdown should cause all the
> backends including waiting ones to exit immediately. At that time, the
> non-acked backend should not return the success, according to the
> definition of sync rep. So we need to change a backend so that it gets rid
> of itself from the waiting queue and exits before returning the success,
> when it receives SIGTERM. This change leads the waiting backends to
> do the same even when pg_terminate_backend is called. But since
> they've not been acked yet, it seems to be reasonable to prevent them
> from returning the COMMIT.
>
> Comments? I'll create the patch barring objection.

The fast smart shutdown part of this problem has been addressed.  The
smart shutdown case still needs work, and I think the consensus was
that your proposal above was the best way to go with it.

Do you still want to work up a patch for this?  If so, I can review.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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