Re: Clean shutdown and warm standby

From: Simon Riggs <simon(at)2ndQuadrant(dot)com>
To: Guillaume Smet <guillaume(dot)smet(at)gmail(dot)com>
Cc: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andreas Pflug <pgadmin(at)pse-consulting(dot)de>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Clean shutdown and warm standby
Date: 2009-05-28 15:36:10
Message-ID: 1243524970.24860.645.camel@ebony.2ndQuadrant
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On Thu, 2009-05-28 at 17:16 +0200, Guillaume Smet wrote:
> On Thu, May 28, 2009 at 5:02 PM, Heikki Linnakangas
> <heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
> > So you check. This solves Guillaume's immediate concern. If you have a
> > suggestion for further improvements, I'm all ears.
>
> Thanks for applying the patch.
>
> Yes, the problem is that before this change, even with a working
> replication and a clean shutdown, you still had to replicate the last
> WAL file by hand. Personnally, I have an eye on each postgresql log
> file when I switch from one server to another so I can see if anything
> is going wrong (that said, it could be a problem with more than 2
> servers...).
>
> This patch just fixes this problem not the other concerns and corner
> cases we might have. If we want to go further, we need to agree on
> what we want exactly and which corner cases we want to cover but it's
> probably 8.5 material at this point.

Your original post wanted to know "we are sure we have all the useful
XLog files when we perform a clean shutdown of master". The patch does
not solve the problem you stated.

You may consider it useful, but a manual check or script execution must
still happen.

If you feel we have moved forwards, that's good, but since no part of
the *safe* maintenance procedure has changed, I don't see that myself.
Only the unsafe way of doing it got faster.

--
Simon Riggs www.2ndQuadrant.com
PostgreSQL Training, Services and Support

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