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Re: Problem with pgstat timneouts

From: "Benjamin Krajmalnik" <kraj(at)servoyant(dot)com>
To: "Benjamin Krajmalnik" <kraj(at)servoyant(dot)com>,"Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "pgsql-admin" <pgsql-admin(at)postgresql(dot)org>
Subject: Re: Problem with pgstat timneouts
Date: 2011-12-30 18:49:03
Message-ID: F4E6A2751A2823418A21D4A160B689888CA5FE@fletch.stackdump.local (view raw or flat)
Thread:
Lists: pgsql-admin
Just a WAG - is it possible this is being caused by the connection
pooler (pgbouncer in my case)?


> -----Original Message-----
> From: pgsql-admin-owner(at)postgresql(dot)org [mailto:pgsql-admin-
> owner(at)postgresql(dot)org] On Behalf Of Benjamin Krajmalnik
> Sent: Thursday, December 22, 2011 11:56 AM
> To: Tom Lane
> Cc: pgsql-admin
> Subject: Re: [ADMIN] Problem with pgstat timneouts
> 
> checkpoint_segments = 1024              # in logfile segments, min 1,
> 16MB each
> checkpoint_timeout = 60min              # range 30s-1h
> checkpoint_completion_target = 0.85     # checkpoint target duration,
> 0.0 - 1.0
> #checkpoint_warning = 30s               # 0 disables
> 
> select * from pg_stat_bgwriter gives ne the following:
> checkpoints_timed - 6887
> checkpoints_req - 36
> 
> A snapshot from the log (I am logging checkpoints)
> 
> 2011-12-22 01:04:33 MST LOG:  checkpoint starting: time
> 2011-12-22 01:12:32 MST WARNING:  pgstat wait timeout
> 2011-12-22 01:12:32 MST WARNING:  pgstat wait timeout
> 2011-12-22 01:13:12 MST WARNING:  pgstat wait timeout
> 2011-12-22 01:13:12 MST WARNING:  pgstat wait timeout
> 2011-12-22 01:13:12 MST WARNING:  pgstat wait timeout
> 2011-12-22 01:13:18 MST WARNING:  pgstat wait timeout
> 2011-12-22 01:13:18 MST WARNING:  pgstat wait timeout
> 2011-12-22 01:35:35 MST WARNING:  pgstat wait timeout
> 2011-12-22 01:35:35 MST WARNING:  pgstat wait timeout
> 2011-12-22 01:38:32 MST WARNING:  pgstat wait timeout
> 2011-12-22 01:38:32 MST WARNING:  pgstat wait timeout
> 2011-12-22 01:41:28 MST LOG:  checkpoint complete: wrote 329593
buffers
> (41.9%); 0 transaction log file(s) added, 0 removed, 731 rec
> 
> 
> 
> 2011-12-22 09:04:33 MST LOG:  checkpoint starting: time
> 2011-12-22 09:06:54 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:06:54 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:06:54 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:07:33 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:07:33 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:07:33 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:13:41 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:22:07 MST ERROR:  canceling autovacuum task
> 2011-12-22 09:22:07 MST CONTEXT:  automatic vacuum of table
> "ishield.public.tbltmptests"
> 2011-12-22 09:28:41 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:28:41 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:31:35 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:31:35 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:33:16 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:33:16 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:33:55 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:33:55 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:33:55 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:35:10 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:35:10 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:35:10 MST ERROR:  canceling autovacuum task
> 2011-12-22 09:35:10 MST CONTEXT:  automatic vacuum of table
> "ishield.public.tbltmptests"
> 2011-12-22 09:36:21 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:36:21 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:37:02 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:37:02 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:37:02 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:37:43 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:37:43 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:38:20 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:38:20 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:38:59 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:38:59 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:38:59 MST WARNING:  pgstat wait timeout
> 2011-12-22 09:42:33 MST LOG:  checkpoint complete: wrote 362856
buffers
> (46.1%); 0 transaction log file(s) added, 0 removed, 908 rec
> 
> I do have an aggressive autovacuum because I have some tables that get
> updated thousands of times per minute and otherwise they bloat
> terribly,
> but it is very seldom that I see cancelation of autovacuum, and only
on
> this table, which is a temporary table  used for the insertion of the
> data, in which records are inserted and deleted - never updated.
> 
> 
> > -----Original Message-----
> > From: Tom Lane [mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us]
> > Sent: Thursday, December 22, 2011 11:45 AM
> > To: Benjamin Krajmalnik
> > Cc: pgsql-admin
> > Subject: Re: [ADMIN] Problem with pgstat timneouts
> >
> > "Benjamin Krajmalnik" <kraj(at)servoyant(dot)com> writes:
> > > The only thing which I see when I run iostat is load on the drives
> > every
> > > so often.  Mifd0 is the database, mifd1 is the pg_xlog.
> >
> > Hmm.  Maybe checkpoints or something else saturating your drives for
> a
> > little while?  You might want to be more aggressive about smoothing
> out
> > checkpoints, cf
> > http://www.westnet.com/~gsmith/content/postgresql/chkp-bgw-83.htm
> > At the very least I'd enable checkpoint logging for awhile and see
> > if there seems to be any correlation to the response-time glitches.
> >
> > 			regards, tom lane
> 
> --
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