Re: xid_wraparound tests intermittent failure.

On 2024-07-25 Th 3:40 PM, Masahiko Sawada wrote:
> On Thu, Jul 25, 2024 at 11:06 AM Masahiko Sawada<sawada(dot)mshk(at)gmail(dot)com> wrote:
>> On Thu, Jul 25, 2024 at 10:56 AM Andrew Dunstan<andrew(at)dunslane(dot)net> wrote:
>>>
>>> On 2024-07-23 Tu 6:59 PM, Masahiko Sawada wrote:
>>>
>>> See<https://bitbucket.org/adunstan/rotfang-fdw/downloads/xid-wraparound-result.tar.bz2>
>>>
>>>
>>> The failure logs are from a run where both tests 1 and 2 failed.
>>>
>>> Thank you for sharing the logs.
>>>
>>> I think that the problem seems to match what Alexander Lakhin
>>> mentioned[1]. Probably we can fix such a race condition somehow but
>>> I'm not sure it's worth it as setting autovacuum = off and
>>> autovacuum_max_workers = 1 (or a low number) is an extremely rare
>>> case. I think it would be better to stabilize these tests. One idea is
>>> to turn the autovacuum GUC parameter on while setting
>>> autovacuum_enabled = off for each table. That way, we can ensure that
>>> autovacuum workers are launched. And I think it seems to align real
>>> use cases.
>>>
>>> Regards,
>>>
>>> [1]https://www.postgresql.org/message-id/02373ec3-50c6-df5a-0d65-5b9b1c0c86d6%40gmail.com
>>>
>>>
>>> OK, do you want to propose a patch?
>>>
>> Yes, I'll prepare and share it soon.
>>
> I've attached the patch. Could you please test if the patch fixes the
> instability you observed?
>
> Since we turn off autovacuum on all three tests and we wait for
> autovacuum to complete processing databases, these tests potentially
> have a similar (but lower) risk. So I modified these tests to turn it
> on so we can ensure the autovacuum runs periodically.
>

I assume you actually meant to remove the "autovacuum = off" in
003_wraparound.pl. With that change in your patch I retried my test, but
on iteration 100 out of 100 it failed on test 002_limits.pl.

You can see the logs at
<https://f001.backblazeb2.com/file/net-dunslane-public/002_limits-failure-log.tar.bz2>

cheers

andrew

--
Andrew Dunstan
EDB:https://www.enterprisedb.com