Re: BUG #18158: Assert in pgstat_report_stat() fails when a backend shutting down with stats pending

Hello hackers,

16.10.2023 12:00, PG Bug reporting form wrote:
> The following bug has been logged on the website:
>
> Bug reference: 18158
> Logged by: Alexander Lakhin
> Email address:exclusion(at)gmail(dot)com
> PostgreSQL version: 16.0
> Operating system: Ubuntu 22.04
> Description:
> ...
> With the following modification in pgstat_flush_pending_entries():
> +if (nowait && (rand() % 10 == 0))
> + did_flush = false;
> +else
> +{
> did_flush = kind_info->flush_pending_cb(entry_ref, nowait);
> +}
>
> the issue reproduced easily:
> make -s check -C src/test/recovery/ PROVE_TESTS="t/012_subtransactions.pl"
> grep TRAP -r src/test/recovery/tmp_check/log
>
> # +++ tap check in src/test/recovery +++
> t/012_subtransactions.pl .. ok
> All tests successful.
> Files=1, Tests=12, 3 wallclock secs ( 0.01 usr 0.00 sys + 0.19 cusr 0.27
> csys = 0.47 CPU)
> Result: PASS
> src/test/recovery/tmp_check/log/012_subtransactions_primary.log:
> TRAP: failed Assert("!pgStatLocal.shmem->is_shutdown"), File: "pgstat.c",
> Line: 616, PID: 2410126

It looks like skink produced this failure yesterday [1]:
241/316 recovery - postgresql:recovery/027_stream_regress ERROR           4374.08s   exit status 1
...
stderr:
#   Failed test 'check contents of pg_stat_statements on regression database'
#   at /home/bf/bf-build/skink/REL_17_STABLE/pgsql/src/test/recovery/t/027_stream_regress.pl line 177.
#          got: 'CREATE|f
# SELECT|t'
#     expected: 'CREATE|t
# DELETE|t
# INSERT|t
# SELECT|t
# UPDATE|t'
# Looks like you failed 1 test of 9.

 pgsql.build/testrun/recovery/027_stream_regress/log/027_stream_regress_primary.log

2026-05-11 14:09:34.397 CEST [4064132][walsender][40/0:0] LOG: released physical replication slot "standby_1"
TRAP: failed Assert("!pgStatLocal.shmem->is_shutdown"), File: "../pgsql/src/backend/utils/activity/pgstat.c", Line: 612,
PID: 4064132
postgres: primary: walsender bf [local] streaming 0/15B4FC98(ExceptionalCondition+0x5f) [0x45ae268]
postgres: primary: walsender bf [local] streaming 0/15B4FC98(pgstat_report_stat+0x14d) [0x4492fe2]
postgres: primary: walsender bf [local] streaming 0/15B4FC98(+0x49315c) [0x449315c]
postgres: primary: walsender bf [local] streaming 0/15B4FC98(shmem_exit+0x78) [0x4448f00]
postgres: primary: walsender bf [local] streaming 0/15B4FC98(+0x449020) [0x4449020]
postgres: primary: walsender bf [local] streaming 0/15B4FC98(proc_exit+0x22) [0x44490c1]
postgres: primary: walsender bf [local] streaming 0/15B4FC98(+0x3f5dbd) [0x43f5dbd]
...
2026-05-11 14:09:34.629 CEST [4063470][postmaster][:0] LOG:  server process (PID 4064132) was terminated by signal 6:
Aborted
2026-05-11 14:09:34.629 CEST [4063470][postmaster][:0] DETAIL: Failed process was running: START_REPLICATION SLOT
"standby_1" 0/3000000 TIMELINE 1
2026-05-11 14:09:34.631 CEST [4063470][postmaster][:0] LOG: terminating any other active server processes

And perhaps (I can't find the full log now) one year ago [2]:
227/305 postgresql:recovery / recovery/027_stream_regress ERROR           3364.50s   exit status 1

[01:19:39.781](0.108s) not ok 9 - check contents of pg_stat_statements on regression database
[01:19:39.781](0.000s) #   Failed test 'check contents of pg_stat_statements on regression database'
#   at /home/bf/bf-build/skink/REL_17_STABLE/pgsql/src/test/recovery/t/027_stream_regress.pl line 173.
[01:19:39.781](0.000s) #          got: 'CREATE|f
# SELECT|t'
#     expected: 'CREATE|t
# DELETE|t
# INSERT|t
# SELECT|t
# UPDATE|t'

I've reproduced such failures with the above modification applied, just
running:
for i in {1..20}; do PROVE_TESTS="t/027*" make -s check -C src/test/recovery/ || break; done

Reproduced on REL_17_STABLE and REL_16_STABLE (starting from dd8008e8e,
which updated 027_stream_regress.pl).

Not reproduced on REL_18_STABLE after 87a6690cc (coming from [3]).

[1] https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=skink&dt=2026-05-11%2010%3A25%3A22
[2] https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=skink&dt=2025-03-18%2023%3A39%3A44
[3] https://www.postgresql.org/message-id/yegnemsijlrhocsfgs7gs7irnczjgkom6fmk2a5u2b66pbvzwi%40ph2h3wppcvdy

Best regards,
Alexander