From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
cc: Robert Haas <robertmhaas@gmail.com>, pgsql-hackers@postgresql.org,
        Thomas Munro <thomas.munro@gmail.com>,
        Andrew Dunstan <andrew@dunslane.net>
Subject: Re: failures in t/031_recovery_conflict.pl on CI
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Comments: In-reply-to Andres Freund <andres@anarazel.de>
	message dated "Sun, 08 May 2022 10:38:44 -0700"
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Date: Sun, 08 May 2022 13:59:09 -0400
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Andres Freund <andres@anarazel.de> writes:
> On 2022-05-08 11:28:34 -0400, Tom Lane wrote:
>> Per lapwing's latest results [1], this wasn't enough.  I'm again thinki=
ng
>> we should pull the whole test from the back branches.

> That failure is different from the earlier failures though. I don't thin=
k it's
> a timing issue in the test like the deadlock check one. I rather suspect=
 it's
> indicative of further problems in this area.

Yeah, that was my guess too.

> Potentially the known problem
> with RecoveryConflictInterrupt() running in the signal handler? I think =
Thomas
> has a patch for that...

Maybe; or given that it's on v10, it could be telling us about some
yet-other problem we perhaps solved since then without realizing
it needed to be back-patched.

> One failure in ~20 runs, on one animal doesn't seem worth disabling the =
test
> for.

No one is going to thank us for shipping a known-unstable test case.
It does nothing to fix the problem; all it will lead to is possible
failures during package builds.  I have no idea whether any packagers
use "make check-world" rather than just "make check" while building.
But if they do, even fairly low-probability failures can be problematic.
(I still carry the scars I acquired while working at Red Hat and being
responsible for packaging mysql: at least back then, their test suite
was full of cases that mostly worked fine, except when getting stressed
in Red Hat's build farm.  Dealing with a test suite that fails 50% of
the time under load, while trying to push out an urgent security fix,
is NOT a pleasant situation.)

I'm happy to have this test in the stable branches once we have committed
fixes that address all known problems.  Until then, it will just be
a nuisance for anyone who is not a developer working on those problems.

			regards, tom lane