The stats.sql test is failing sporadically in v14- on POWER7/AIX 7.1 buildfarm animals

Hello hackers,

Yesterday, the buildfarm animal sungazer was benevolent enough to
demonstrate a rare anomaly, related to old stats collector:
test stats                        ... FAILED   469155 ms

========================
 1 of 212 tests failed.
========================

--- /home/nm/farm/gcc64/REL_14_STABLE/pgsql.build/src/test/regress/expected/stats.out 2022-03-30 01:18:17.000000000 +0000
+++ /home/nm/farm/gcc64/REL_14_STABLE/pgsql.build/src/test/regress/results/stats.out 2024-07-30 09:49:39.000000000 +0000
@@ -165,11 +165,11 @@
   WHERE relname like 'trunc_stats_test%' order by relname;
        relname      | n_tup_ins | n_tup_upd | n_tup_del | n_live_tup | n_dead_tup
-------------------+-----------+-----------+-----------+------------+------------
-  trunc_stats_test  |         3 |         0 |         0 | 0 |          0
-  trunc_stats_test1 |         4 |         2 |         1 | 1 |          0
-  trunc_stats_test2 |         1 |         0 |         0 | 1 |          0
-  trunc_stats_test3 |         4 |         0 |         0 | 2 |          2
-  trunc_stats_test4 |         2 |         0 |         0 | 0 |          2
+  trunc_stats_test  |         0 |         0 |         0 | 0 |          0
+  trunc_stats_test1 |         0 |         0 |         0 | 0 |          0
+  trunc_stats_test2 |         0 |         0 |         0 | 0 |          0
+  trunc_stats_test3 |         0 |         0 |         0 | 0 |          0
+  trunc_stats_test4 |         0 |         0 |         0 | 0 |          0
...

inst/logfile contains:
2024-07-30 09:25:11.225 UTC [63307946:1] LOG:  using stale statistics instead of current ones because stats collector is
not responding
2024-07-30 09:25:11.345 UTC [11206724:559] pg_regress/create_index LOG:  using stale statistics instead of current ones
because stats collector is not responding
...

That's not the only failure of that kind occurred on sungazer, there were
also [2] (REL_13_STABLE), [3] (REL_13_STABLE), [4] (REL_12_STABLE).
Moreover, such failures were produced by all the other POWER7/AIX 7.1
animals: hornet ([5], [6]), tern ([7], [8]), mandrill ([9], [10], ...).
But I could not find such failures coming from POWER8 animals: hoverfly
(running AIX 7200-04-03-2038), ayu, boa, chub, and I did not encounter such
anomalies on x86 nor ARM platforms.

Thus, it looks like this stats collector issue is only happening on this
concrete platform, and given [11], I think such failures perhaps should
be just ignored for the next two years (until v14 EOL) unless AIX 7.1
will be upgraded and we see them on a vendor-supported OS version.

So I'm parking this information here just for reference.

[1] https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=sungazer&dt=2024-07-30%2003%3A49%3A35
[2] https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=sungazer&dt=2023-02-09%2009%3A29%3A10
[3] https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=sungazer&dt=2022-06-16%2009%3A52%3A47
[4] https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=sungazer&dt=2023-12-13%2003%3A40%3A42
[5] https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=hornet&dt=2024-03-29%2005%3A27%3A09
[6] https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=hornet&dt=2024-03-19%2002%3A09%3A07
[7] https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=tern&dt=2022-12-16%2009%3A17%3A38
[8] https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=tern&dt=2021-04-01%2003%3A09%3A38
[9] https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=mandrill&dt=2021-04-05%2004%3A22%3A17
[10] https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=mandrill&dt=2021-07-12%2004%3A31%3A37
[11] https://www.postgresql.org/message-id/3154146.1697661946%40sss.pgh.pa.us

Best regards,
Alexander