Re: LISTEN/NOTIFY testing woes

On 11/23/19 5:01 PM, Tom Lane wrote:
> I ran into a couple of issues while trying to devise a regression test
> illustrating the LISTEN-in-serializable-transaction issue Mark Dilger
> reported. The first one is that an isolation test in which we expect
> to see a cross-process NOTIFY immediately after a COMMIT turns out to
> be not very stable: on my machine, it works as long as you're just
> running the isolation tests by themselves, but it usually falls over
> if I'm running check-world with any amount of parallelism. The reason
> for this seems to be that incoming notifies are only checked for when
> we're about to wait for client input. At that point we've already
> sent the ReadyForQuery ('Z') protocol message, which will cause libpq
> to stand down from looking for more input and return a null from
> PQgetResult(). Depending on timing, the following Notify protocol
> messages might arrive quickly enough that isolationtester.c sees them
> before it goes off to do something else, but that's not very reliable.

Thanks for working on this, Tom.

I have finished reading and applying your three patches and have moved
on to testing them. I hope to finish the review soon.

--
Mark Dilger