Re: [Skytools-users] WAL Shipping + checkpoint

From: Mark Kirkwood <mark(dot)kirkwood(at)catalyst(dot)net(dot)nz>
To: Sébastien Lardière <slardiere(at)hi-media(dot)com>
Cc: pgsql-general(at)postgresql(dot)org, skytools-users(at)pgfoundry(dot)org
Subject: Re: [Skytools-users] WAL Shipping + checkpoint
Date: 2009-08-26 02:46:58
Message-ID: 4A94A222.90507@catalyst.net.nz
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Sébastien Lardière wrote:
> Hi All,
>
> I've a cluster ( Pg 8.3.7 ) with WAL Shipping, and a few hours ago,
> the master had to restart.
>
> I use walmgr from Skytools, which works very well.
>
> I have already restart the master without any problem, but today, the
> slave doesn't work like I want. The field "Time of latest checkpoint"
> from the pg_controldata on the slave keep the same values, but WAL
> File are processed correctly.
>
> I try to restart the slave, but, after processed again all the WAL
> between "Time of latest checkpoint" and, it does nothing else, latest
> checkpoint stay at the same value.
>
> I don't know if it's important ( i think so ), and I can't fix it.
>
It is normal for it to lag behind somewhat on the slave (depending on
what your checkpoint timeout etc settings are).

However, I've noticed what you are seeing as well - particularly when
there are no actual data changes coming through in the logs - the slave
checkpoint time does not change even tho there have been checkpoints on
the master (I may have a look in the code to see what the story really
is...if I have time).

Cheers

Mark

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