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Re: WARNING: pgstat wait timeout

From: Magnus Hagander <magnus(at)hagander(dot)net>
To: Greg Smith <greg(at)2ndquadrant(dot)com>
Cc: Matteo Beccati <php(at)beccati(dot)com>, Jaime Casanova <jcasanov(at)systemguards(dot)com(dot)ec>, "Sergey E(dot) Koposov" <math(at)sai(dot)msu(dot)ru>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: WARNING: pgstat wait timeout
Date: 2010-01-29 13:16:04
Message-ID: 9837222c1001290516j461e0e5eu19aa92a7da583f56@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
2010/1/29 Greg Smith <greg(at)2ndquadrant(dot)com>:
> I just found a few of these errors in a log file during some pgbench testing tonight.  Linux, recent CVS HEAD; given the range of systems and versions this has been reported against now, this bug doesn't look like a platform or version/build specific issue.
>
> Unfortunately the instance I had up wasn't setup very well for logging, but I did notice that all of the ones I saw had nearby messages about autovacuum issues, which seems to match Tom's earlier suggestion at http://archives.postgresql.org/pgsql-bugs/2009-07/msg00083.php that the source of the warning (but not necessarily the underlying problem) for these is the autovacuum launcher complaining; here's two different sets:
>
> ERROR:  canceling autovacuum task
> CONTEXT:  automatic analyze of table "pgbench.public.pgbench_accounts"
> WARNING:  pgstat wait timeout
> WARNING:  pgstat wait timeout
> ERROR:  canceling autovacuum task
> CONTEXT:  automatic analyze of table "pgbench.public.pgbench_accounts"
>
> WARNING:  pgstat wait timeout
> ERROR:  canceling autovacuum task
> CONTEXT:  automatic analyze of table "pgbench.public.pgbench_accounts"
> ERROR:  canceling autovacuum task
> CONTEXT:  automatic analyze of table "pgbench.public.pgbench_accounts"
>
> Because of what I'm (not) seeing in pg_stat_bgwriter, I'm suspicious that its underlying work or messages may be involved here.  I'm not seeing the sort of totals I expect in that view after these large bouts of activity.  Now, my use tonight has included the new pg_stat_reset_shared('bgwriter') to clear out those stats between runs, so perhaps that's involved too.  Guessing not only because of the reports going back to 8.4 that also have this error message.
>
> Will keep an eye out for this one now that I know I might run into it, have already cranked up the logging and will look for something reproducible to gather more info.

I've seen this happen semi-frequently during initdb on win32 on an
Amazon EC2 image. I attributed it to the combination of windows and
overloaded virtualization, but it may just be that it shows up more
often there.

-- 
 Magnus Hagander
 Me: http://www.hagander.net/
 Work: http://www.redpill-linpro.com/

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