Horton

Re: Testing LISTEN/NOTIFY more effectively

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
Cc: pgsql-hackers@lists.postgresql.org
Date: 2019-07-27T23:45:15Z
Lists: pgsql-hackers

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I wrote:
> Andres Freund <andres@anarazel.de> writes:
>> Hm. I wonder if all that's happening with prairedog is that the notice
>> is sent a bit later. I think that could e.g. conceivably happen because
>> it TCP_NODELAY isn't supported on prariedog? Or just because the machine
>> is very slow?

> The notices (not notifies) are coming out in the opposite order from
> expected.  I haven't really thought hard about what's causing that;
> it seems odd, because isolationtester isn't supposed to give up waiting
> for a session until it's visibly blocked according to pg_locks.  Maybe
> it needs to recheck for incoming data once more after seeing that?

Ah-hah, that seems to be the answer.  With the attached patch I'm
getting reliable-seeming passes on prairiedog.

			regards, tom lane

Commits

  1. Improve test coverage for LISTEN/NOTIFY.

  2. Don't drop NOTICE messages in isolation tests.

  3. Fix isolationtester race condition for notices sent before blocking.