Message-ID: <53370026.2040509@aklaver.com>
Date: Sat, 29 Mar 2014 10:17:26 -0700
From: Adrian Klaver <adrian.klaver@aklaver.com>
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To: Willy-Bas Loos <willybas@gmail.com>, lst_hoe02@kwsoft.de
CC: pgsql-admin <pgsql-admin@postgresql.org>,
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Subject: Re: [ADMIN]openvz and shared memory trouble
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On 03/29/2014 08:19 AM, Willy-Bas Loos wrote:
> The error that shows up is a Bus error.
> That's on the replication slave.
> Here's the log about it:
> 2014-03-29 12:41:33 CET db: ip: us: FATAL:  could not receive data from
> WAL stream: server closed the connection unexpectedly
>          This probably means the server terminated abnormally
>          before or while processing the request.
>
> cp: cannot stat
> `/data/postgresql/9.1/main/wal_archive/00000001000000720000000A': No
> such file or directory
> 2014-03-29 12:41:33 CET db: ip: us: LOG:  unexpected pageaddr
> 71/E9DA0000 in log file 114, segment 10, offset 14286848
> cp: cannot stat
> `/data/postgresql/9.1/main/wal_archive/00000001000000720000000A': No
> such file or directory
> 2014-03-29 12:41:33 CET db: ip: us: LOG:  streaming replication
> successfully connected to primary
> 2014-03-29 12:41:48 CET db: ip: us: LOG:  startup process (PID 17452)
> was terminated by signal 7: Bus error
> 2014-03-29 12:41:48 CET db: ip: us: LOG:  terminating any other active
> server processes
> 2014-03-29 12:41:48 CET db:wbloos ip:[local] us:wbloos WARNING:
> terminating connection because of crash of another server process
> 2014-03-29 12:41:48 CET db:wbloos ip:[local] us:wbloos DETAIL:  The
> postmaster has commanded this server process to roll back the current
> transaction and exit, because another server process exited abnormally
> and possibly corrupted shared memory.
> 2014-03-29 12:41:48 CET db:wbloos ip:[local] us:wbloos HINT:  In a
> moment you should be able to reconnect to the database and repeat your
> command.
>

Well what I am seeing are WAL log errors. One saying no file is
present, the other pointing at a possible file corruption. Shared memory 
problems are offered as a possible cause only. Right now I would say we 
are seeing only half the picture. The Postgres logs from the same time 
period for the primary server, as well as the system logs for the openvz 
container would help fill in the other half of the picture.


>
>
> On Fri, Mar 28, 2014 at 2:52 PM, Adrian Klaver
> <adrian.klaver@aklaver.com <mailto:adrian.klaver@aklaver.com>> wrote:
>
>
>     25% is a suggested value, not an absolute value. Desirable would
>     seem to be a value that works for your situation and maintains
>     performance. Is there any indication that running with a lower value
>     adversely affects performance?
>
>

>
> Thanks, i'm looking into the bean counters more.
> Maybe there is something to won by guaranteeing the shared memory
> resources, instead of just refraining from constraining them.
>

>
> Ok, that sounds reassuring, and i agree that the other posts are not
> really related. It's just that i found several posts that boiled down to
> memory related issues with openVZ, and experts complaining. That made me
> worry.

A cursory look at memory management in openvz shows it is different from 
other virtualization software and physical machines. Whether that is a 
problem would seem to be dependent on where you are on the learning 
curve:) As to 'experts' complaining, I have heard a lot of that in many 
different fields and every once in while they are right, so it tends to 
be low on my check list when it comes to doing things.


-- 
Adrian Klaver
adrian.klaver@aklaver.com


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