Re: Drop replslot after pgstat_shutdown cause assert coredump

I said:
> Considering the coming shared-memory based stats collector, pgstat
> must be shutdown before shared memory shutdown. Every operation that
> requires stats collector also must be shut down before the pgstat
> shutdown. A naive solution would be having before-pgstat-shutdown hook
> but I'm not sure it's the right direction.

For this particular issue, we can add an explicit initilization phase
of replication slot per backend, which simply registers before_shmem
callback. It would work fine unless we carelessly place the
initialization before pgstat_initialize() (not pgstat_init()) call.

(Honestly, I haven't been able to reproduce the issue itself for
myself yet..)

> > on_proc_exit_list (I'm not sure if this change is safe, though).
> > Or maybe pgstat logic for replication slot drop needs to be
> > overhauled.
>
> I think we don't want to lose the stats numbers of the to-be-dropped
> slot. So the slot-drop must happen before pgstat shutdown.

I haven't sought other similar issues. I'm going to check it if they,
if any, can be fixe the same way.

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center