Re: pgsql: Improve runtime and output of tests for replication slots checkp

On Sat, Jun 21, 2025 at 1:25 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> I wrote:
> > But in the buildfarm failures I don't see any 'checkpoint complete'
> > before the shutdown.
>
> Ooops, I lied: we have at least one case where the checkpoint does
> finish but then it hangs up anyway:
>
> https://buildfarm.postgresql.org/cgi-bin/show_stage_log.pl?nm=melonworm&dt=2025-06-20%2019%3A59%3A31&stg=recovery-check
>
> 2025-06-20 20:05:32.548 UTC [3171474][client backend][61/2:0] LOG: statement: select injection_points_wakeup('checkpoint-before-old-wal-removal')
> 2025-06-20 20:05:32.550 UTC [3162113][checkpointer][:0] LOG: checkpoint complete: wrote 1 buffers (0.0%), wrote 0 SLRU buffers; 0 WAL file(s) added, 0 removed, 0 recycled; write=0.045 s, sync=0.001 s, total=1.507 s; sync files=1, longest=0.001 s, average=0.001 s; distance=327688 kB, estimate=327688 kB; lsn=0/290020C0, redo lsn=0/29002068
> 2025-06-20 20:05:32.551 UTC [3171474][client backend][:0] LOG: disconnection: session time: 0:00:00.073 user=bf database=postgres host=[local]
> 2025-06-20 20:05:32.552 UTC [3170563][client backend][:0] LOG: disconnection: session time: 0:00:01.538 user=bf database=postgres host=[local]
> 2025-06-20 20:05:32.564 UTC [3163446][client backend][7/146:0] LOG: statement: SELECT 1
> 2025-06-20 20:05:32.564 UTC [3161873][postmaster][:0] LOG: received immediate shutdown request
> 2025-06-20 20:05:32.604 UTC [3161873][postmaster][:0] LOG: database system is shut down
>
> I'm still confused about whether the 046 script intends to
> sometimes test cases where the checkpoint doesn't have time to
> complete. But it seems that whatever is going on here
> is a bit subtle and platform-dependent.

I think this indicates unfinished intention to wait for checkpoint
completion. But I think both cases (checkpoint finished and
unfinished) should work correctly. So, I believe there is a backend
problem. I'm trying to reproduce this locally. Sorry for the
confusion.

------
Regards,
Alexander Korotkov
Supabase