Re: xid_wraparound tests intermittent failure.

On 2024-07-21 Su 1:34 PM, Tom Lane wrote:
> Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
>> I noticed this when working on the PostgreSQL::Test::Session project I
>> have in hand. All the tests pass except occasionally the xid_wraparound
>> tests fail. It's not always the same test script that fails either. I
>> tried everything but couldn't make the failure stop. So then I switched
>> out my patch so it's running on plain master and set things running in a
>> loop. Lo and behold it can be relied on to fail after only a few
>> iterations.
> I have been noticing xid_wraparound failures in the buildfarm too.
> They seemed quite infrequent, but it wasn't till just now that
> I realized that xid_wraparound is not run by default. (You have to
> put "xid_wraparound" in PG_TEST_EXTRA to enable it.) AFAICS the
> only buildfarm animals that have enabled it are dodo and perentie.
> dodo is failing this test fairly often:
>
> https://buildfarm.postgresql.org/cgi-bin/show_history.pl?nm=dodo&br=HEAD
>
> perentie doesn't seem to be having a problem, but I will bet that
> part of the reason is it's running with cranked-up timeouts:
>
> 'build_env' => {
> 'PG_TEST_EXTRA' => 'xid_wraparound',
> 'PG_TEST_TIMEOUT_DEFAULT' => '360'
> },
>
> One thing that seems quite interesting is that the test seems to
> take about 10 minutes when successful on dodo, but when it fails
> it's twice that. Why the instability? (Perhaps dodo has highly
> variable background load, and the thing simply times out in some
> runs but not others?)
>
> Locally, I've not managed to reproduce the failure yet; so perhaps
> there is some platform dependency. What are you testing on?

Linux ub22arm 5.15.0-116-generic #126-Ubuntu SMP Mon Jul 1 10:08:40 UTC
2024 aarch64 aarch64 aarch64 GNU/Linux

It's a VM running on UTM/Apple Silicon

cheers

andrew

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