Re: BUG #4879: bgwriter fails to fsync the file in recovery mode

From: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Simon Riggs <simon(at)2ndQuadrant(dot)com>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, pgsql-bugs(at)postgresql(dot)org
Subject: Re: BUG #4879: bgwriter fails to fsync the file in recovery mode
Date: 2009-06-25 15:12:16
Message-ID: 4A4393D0.70804@enterprisedb.com
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Tom Lane wrote:
> Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:
>> In archive recovery, we always start bgwriter at the beginning of WAL
>> replay. In crash recovery, we don't start bgwriter until the end of wAL
>> replay. So we could change the "!isRedo" condition to
>> "!InArchiveRecovery". It's not a very clean solution, but it's simple.
>
> This is probably what is needed. We need to look around for other tests
> of "in redo" that have been obsoleted by the change in bgwriter
> behavior.

We have another problem with the end-of-recovery checkpoint. When the
startup process does the checkpoint, it won't know to perform the
pending fsyncs() the bgwriter has absorbed.

A short fix would be to have bgwriter do the shutdown checkpoint instead
in archive recovery. I don't recall if there was a reason it wasn't
coded like that to begin with, though.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com

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