Re: subscriptionCheck failures on nightjar

From: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, Andres Freund <andres(at)anarazel(dot)de>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: subscriptionCheck failures on nightjar
Date: 2019-09-17 19:45:10
Message-ID: 20190917194510.iqwyl3be62pz7l27@development
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On Tue, Sep 17, 2019 at 12:39:33PM -0400, Tom Lane wrote:
>Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> On Mon, Aug 26, 2019 at 9:29 AM Tomas Vondra
>> <tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
>>> This is one of the remaining open items, and we don't seem to be moving
>>> forward with it :-(
>> Why exactly is this an open item, anyway?
>The reason it's still here is that Andres expressed a concern that
>there might be more than meets the eye in this. What meets the eye
>is that PANICing on file-not-found is not appropriate here, but Andres
>seemed to think that the file not being present might reflect an
>actual bug not just an expectable race condition [1].
>Personally I'd be happy just to treat it as an expectable case and
>fix the code to not PANIC on file-not-found.

FWIW I agree with Andres that there probably is an actual bug. The file
should not just disappear like this, it's clearly unexpected so the
PANIC does not seem entirely inappropriate.

I've tried reproducing the issue on my local systems, with the extra
sleeps between fsyncs and so on, but I haven't managed to trigger it so
far :-(

>In either case, it probably belongs in the "older bugs" section;
>nightjar is showing the same failure on v11 from time to time.

Yes, it should be moved to the older section - it's clearly a v11 bug.


Tomas Vondra
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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