Re: Failure in subscription test 004_sync.pl

On Mon, Jun 14, 2021 at 10:41 AM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>
> >
> > I think it is showing a race condition issue in the code. In
> > DropSubscription, we first stop the worker that is receiving the WAL,
> > and then in a separate connection with the publisher, it tries to drop
> > the slot which leads to this error. The reason is that walsender is
> > still active as we just wait for wal receiver (or apply worker) to
> > stop. Normally, as soon as the apply worker is stopped the walsender
> > detects it and exits but in this case, it took some time to exit, and
> > in the meantime, we tried to drop the slot which is still in use by
> > walsender.
>
> There might be possible.
>
> That's weird since DROP SUBSCRIPTION executes DROP_REPLICATION_SLOT
> command with WAIT option. I found a bug that is possibly an oversight
> of commit 1632ea4368.
>
..
>
> The condition should be the opposite; we should raise the error when
> 'nowait' is true. I think this is the cause of the test failure. Even
> if DROP SUBSCRIPTION tries to drop the slot with the WAIT option, we
> don't wait but raise the error.
>
> Attached a small patch fixes it.
>

Yes, this should fix the recent buildfarm failures. Alvaro, would you
like to take care of this?

-- 
With Regards,
Amit Kapila.