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List:       postgresql-admin
Subject:    Re: [ADMIN] pg_stat_activity showing non-existent processes
From:       Jerry Sievers <jerry () jerrysievers ! com>
Date:       2006-03-27 0:32:29
Message-ID: m3mzfczq02.fsf () prod01 ! jerrysievers ! com
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Tom Lane <tgl@sss.pgh.pa.us> writes:

> Jerry Sievers <jerry@jerrysievers.com> writes:
> > At any rate; I'm wondering what possible causes might be responsible
> > for pg_stat_activity's underlying functions to lose track of the valid
> > process list?
> 
> It sounds like the stats collector missed a few "backend quit"
> messages.  This isn't real surprising: the stats messaging mechanism is
> intentionally designed to drop messages under severe load, rather than
> slow down backends.

Tom, I appreciate your comments on this.

> We recently put in a filter that prevents reporting pg_stat_activity
> lines for backends that are dead according to the up-to-date list in
> shared memory.  I don't think that's in 8.0.3 though.

This machine is going to be upgraded to 8.1 ASAP.

In the meantime, I may adjust the cron run time for the batch job that
terminates these sessions in case it's running concurrently with other
batch traffic.

I believe the thing runs hourly at the 00 minute and this may likely
be a time that we're kicking off all sorts of other jobs too.


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