Re: Re: [COMMITTERS] pgsql: Make standby server continuously retry restoring the next WAL

From: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
To: Simon Riggs <simon(at)2ndQuadrant(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, Aidan Van Dyk <aidan(at)highrise(dot)ca>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Re: [COMMITTERS] pgsql: Make standby server continuously retry restoring the next WAL
Date: 2010-03-25 10:47:07
Message-ID: 4BAB3F2B.9030405@enterprisedb.com
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Heikki Linnakangas wrote:
> Simon Riggs wrote:
>> On Thu, 2010-03-25 at 10:11 +0200, Heikki Linnakangas wrote:
>>
>>> PANIC seems like the appropriate solution for now.
>> It definitely is not. Think some more.
>
> Well, what happens now in previous versions with pg_standby et al is
> that the standby starts up. That doesn't seem appropriate either.
>
> Hmm, it would be trivial to just stay in the standby mode at a corrupt
> file, continuously retrying to restore it and continue replay. If it's
> genuinely corrupt, it will never succeed and the standby gets stuck at
> that point. Maybe that's better; it's close to what Fujii suggested
> except that you don't need a new mode for it.

On second thought, that's easy for the built-in standby mode, but not
for archive recovery where we're not currently retrying anything. In
archive recovery, we could throw a WARNING and start up, which would be
like the current behavior in older versions except you get a WARNING
instead of LOG, or we could PANIC. I'm leaning towards PANIC, which
makes most sense for genuine point-in-time or archive recovery (ie. not
a standby server), but I can see the rationale for WARNING too, for
pg_standby and for the sake of preserving old behavior.

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

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