Re: Race conditions in 019_replslot_limit.pl

Andres Freund <andres@anarazel.de> writes:
> Seems to suggest something is holding a problematic lock in a way that I do not understand yet:

> https://buildfarm.postgresql.org/cgi-bin/show_stage_log.pl?nm=crake&dt=2022-02-23%2013%3A47%3A20&stg=recovery-check
> 2022-02-23 09:09:52.299 EST [2022-02-23 09:09:52 EST 1997084:6] 019_replslot_limit.pl LOG:  received replication
command:CREATE_REPLICATION_SLOT "pg_basebackup_1997084" TEMPORARY PHYSICAL ( RESERVE_WAL) 
> ...
> 2022-02-23 09:09:52.518 EST [2022-02-23 09:09:52 EST 1997084:14] 019_replslot_limit.pl DEBUG:  shmem_exit(0): 4
before_shmem_exitcallbacks to make 
> 2022-02-23 09:09:52.518 EST [2022-02-23 09:09:52 EST 1997084:15] 019_replslot_limit.pl DEBUG:  replication slot exit
hook,without active slot 
> 2022-02-23 09:09:52.518 EST [2022-02-23 09:09:52 EST 1997084:16] 019_replslot_limit.pl DEBUG:  temporary replication
slotcleanup: begin 

> last message from 1997084 until the immediate shutdown.

Hmm.  Maybe put a couple more debug messages into ReplicationSlotCleanup
and/or ReplicationSlotDropPtr?  It doesn't seem very clear where in that
sequence it's hanging up.

> We could be more certain if we shut down the cluster in fast rather than
> immediate mode. So I'm thinking of doing something like

Does that risk an indefinite hangup of the buildfarm run?

            regards, tom lane