From: Jerry Sievers <gsievers19@comcast.net>
To: John Scalia <jayknowsunix@gmail.com>
Cc: "pgsql-admin\@postgresql.org" <pgsql-admin@postgresql.org>
Subject: Re: Error messages in a hot standby server's logfiles
References: <5434239E.50508@gmail.com>
Date: Tue, 07 Oct 2014 12:56:14 -0500
In-Reply-To: <5434239E.50508@gmail.com> (John Scalia's message of "Tue, 07 Oct
 2014 13:32:14 -0400")
Message-ID: <86d2a3zrup.fsf@jerry.enova.com>
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John Scalia <jayknowsunix@gmail.com> writes:

> Hi all,
>
> My setup is: postgresql V9.3.3 running on a CentOS 6.5 (kernel
> 2.6.32-358.18.1.el6.x86_64) and I have 3 servers, one primary and two
> hot standbys. In our failover and loss of communications testing, I
> have seen a couple of issues that I'm hard to explain. For instance,
> we took one hot standby out of service by shutting down postgresql on
> it. Now, we're hot standby with log shipping as an insurance policy,
> so the WAL segments continued to be copied onto that out of service
> standby for a few minutes. On restart, I see:
>
> cp: cannot stat '/mnt/wallogs/archive/0000000C.history': No such file or directory
> cp: cannot stat '/mnt/wallogs/archive/0000000B0000001900000077': No such file or directory
>
> Later in the logfile, I see another failure for 000000B.history.

These .history files may or may not exist depending on whether timeline
branching has been done.

The only way Pg knows how to check for them is invoking archive_command
which is your case is cp and thus the message.

HTH

>
> In looking at the /mnt/wallogs/archive directory, those files aren't
> there, but as the primary never had an issue and continued to copy WAL
> segments to this directory, why was the standby looking for them? What
> triggered this? Also, in that directory, I often see files generated
> by the pg_basebackup command used to build the standby, files like
> "0000000B0000001900000000.00000028.backup" or generally files ending
> with .backup in their names. These never get removed automatically by
> the standby server. We have to manually remove them. So, I'm guessing
> they weren't necessary, so why did the primary copy them here using
> its archive_command? Why aren't they removed by some mechanism on the
> standby?
>
> --
> Jay

-- 
Jerry Sievers
Postgres DBA/Development Consulting
e: postgres.consulting@comcast.net
p: 312.241.7800


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