Re: Race conditions with TAP test for syncrep

On Mon, Jun 17, 2019 at 10:50:39AM -0400, Alvaro Herrera wrote:
> Hmm, this introduces a bit of latency: it waits for each standby to be
> fully up before initializing the next standby. Maybe it would be more
> convenient to split the primitives: keep the current one to start the
> standby, and add a separate one to wait for it to be registered. Then
> we could do
> standby1->start;
> standby2->start;
> standby3->start;
> foreach my $sby (@standbys) {
> $sby->wait_for_standby
> }

It seems to me that this sequence could still lead to inconsistencies:
1) standby 1 starts, reaches consistency so pg_ctl start -w exits.
2) standby 2 starts, reaches consistency.
3) standby 2 starts a WAL receiver, gets the first WAL sender slot of
the primary.
4) standby 1 starts a WAL receiver, gets the second slot.

> I think this should be note() rather than print(), or maybe diag(). (I
> see that we have a couple of other cases which use print() in the tap
> tests, which I think should be note() as well.)

OK. Let's change it for this patch. For the rest, I can always send
a different patch. Just writing down your comment..
--
Michael