From: Tom Lane <tgl@sss.pgh.pa.us>
To: Justin Pryzby <pryzby@telsasoft.com>
cc: Thomas Munro <thomas.munro@gmail.com>,
        pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: stress test for parallel workers
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Comments: In-reply-to Justin Pryzby <pryzby@telsasoft.com>
	message dated "Tue, 23 Jul 2019 18:04:40 -0500"
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Date: Tue, 23 Jul 2019 19:29:04 -0400
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Justin Pryzby <pryzby@telsasoft.com> writes:
> I want to say I'm almost certain it wasn't ENOSPC in other cases, since,
> failing to find log output, I ran df right after the failure.

The fact that you're not finding log output matching what was reported
to the client seems to me to be a mighty strong indication that there
*was* an ENOSPC problem.  Can you reconfigure to put the postmaster
log on a different volume?

> But that gives me an idea: is it possible there's an issue with files being
> held opened by worker processes ?  Including by parallel workers?  Probably
> WALs, even after they're rotated ?  If there were worker processes holding
> opened lots of rotated WALs, that could cause ENOSPC, but that wouldn't be
> obvious after they die, since the space would then be freed.

Parallel workers aren't ever allowed to write, in the current
implementation, so it's not real obvious why they'd have any
WAL log files open at all.

			regards, tom lane