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Re: warning message in standby

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Bruce Momjian <bruce(at)momjian(dot)us>, Magnus Hagander <magnus(at)hagander(dot)net>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: warning message in standby
Date: 2010-06-30 02:11:06
Message-ID: AANLkTilVlMCs5v_TvL_OUivbw2GgmCV8WmYR2XKF0drK@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Tue, Jun 29, 2010 at 10:03 PM, Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
> This is true. But what I'm concerned about is:
>
> 1. Backend writes and fsyncs the WAL to the disk
> 2. The WAL on the disk gets corrupted
> 3. Walsender reads and sends that corrupted WAL image
> 4. The master crashes because of the corruption of the disk
> 5. The standby attempts to replay the corrupted WAL... PANIC

That sounds like design behavior to me.

>> Well, if we want to leave it up to the user/clusterware, the current
>> code is possibly adequate, although there are many different log
>> messages that could signal this situation, so coding it up might not
>> be too trivial.
>
> So the current code + user-settable-retry-count seems good to me.
> If the retry-count is set to 0, we will not see the repeated log
> messages. And we might need to provide the parameter specifying
> how the standby should behave after exceeding the retry-count:
> PANIC or stay-alive-without-retries.
>
> Choosing PANIC and using the retry-count = 5 would cover your proposed
> patch.

I'm still having a hard time understanding why anyone would want to
configure this value as infinity.

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

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