Re: Check that streaming replica received all data after master shutdown

From: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
To: Vladimir Borodin <root(at)simply(dot)name>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Check that streaming replica received all data after master shutdown
Date: 2015-01-13 16:42:27
Message-ID: 20150113164227.GG1663@alvh.no-ip.org
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Vladimir Borodin wrote:

> I’m not sure that these 104 bytes will always be 104 bytes to have a
> strict equality while checking. Could it change in the future?

There is no promise that WAL record format stays unchanged. Sometimes
we change a WAL record in a minor release.

> Or is there a better way to understand that streaming replica received
> all data after master shutdown? The check that pg_xlog_location_diff
> returns 104 bytes seems a bit strange.

I guess you could pg_xlogdump the difference and verify that it is a
shutdown checkpoint record. As far as I remember there should always be
one at the end of recovery.

--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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