Re: [HACKERS] Timing-sensitive case in src/test/recovery TAP tests

On Mon, Jun 26, 2017 at 11:44 AM, Craig Ringer <craig@2ndquadrant.com> wrote:
> On 26 June 2017 at 10:09, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Michael Paquier <michael.paquier@gmail.com> writes:
>>> On Mon, Jun 26, 2017 at 10:48 AM, Craig Ringer <craig@2ndquadrant.com> wrote:
>>>> $node_standby_1->poll_query_until('postgres', q[SELECT xmin IS NULL
>>>> from pg_replication_slots WHERE slot_name = '] . $slotname_2 . q[']);
>>
>>> +1 for avoiding a sleep call if it is not necessary. Fast platforms
>>> would always pay a cost on that, and slow platforms would wait 1s (or
>>> more!) when polling for the result.
>>
>>> Could it be possible to remove as well the second sleep(2) call in
>>> this test please?
>>
>> Yes, I'd like to see those fixed sleeps go away too.  Want to work
>> on a concrete patch?
>
>
> Attached.

Thanks for the patch.

As long as we are on it, there is this code block in the test:
my ($xmin, $catalog_xmin) = get_slot_xmins($node_master, $slotname_1);
is($xmin,         '', 'non-cascaded slot xmin null with no hs_feedback');
is($catalog_xmin, '', 'non-cascaded slot xmin null with no hs_feedback');

($xmin, $catalog_xmin) = get_slot_xmins($node_standby_1, $slotname_2);
is($xmin,         '', 'cascaded slot xmin null with no hs_feedback');
is($catalog_xmin, '', 'cascaded slot xmin null with no hs_feedback');

This should be more verbose as the 2nd and 4th test should say
"catalog xmin" instead of xmin.

Also, wouldn't it be better to poll as well node_standby_1's
pg_replication_slot on slotname_2? It would really seem better to make
the nullness check conditional in get_slot_xmins instead. Sorry for
changing opinion here.
-- 
Michael