On Wed, 2022-08-24 at 14:18 +0900, Kyotaro Horiguchi wrote:
> At Fri, 19 Aug 2022 18:37:53 +0200, Laurenz Albe <laurenz.albe@cybertec.at> wrote in
> > On Fri, 2022-08-19 at 16:54 +0200, Giovanni Biscontini wrote:
> > > Hello everyone,
> > > I'm experiencing a behaviour I don't really understand if is a misconfiguration or a wanted behaviour:
> > > 1) I set up a primary server (a.k.a. db1) with and archive_command to a storage
> > > 2) I set up a replica (a.k.a. db2) that created a slot named as slot_2 and that has the recovery_command
> > > set to read archived wal on the storage.
> > > If I shutdown replica db2 during a pgbench I see the safe_wal_size queried from pg_replication_slots
> > > on the primary decrease to a certain amount but still in the max_slot_wal_kepp_size window: even
> > > if I restart the replica db2 before the slot_state changes to unreserved or lost I see that the
> > > replica gets needed wals from the storage using recovery_command but doesn't use slot on primary.
> > > Only if I comment the recovery command on the .conf of the replica then it uses slot.
> > > If this is a wanted behaviour I can't understand the need of slots on primary.
> >
> > This is normal behavior and is no problem.
> >
> > After the standby has caught up using "restore_command", it will connection to
> > the primary as defined in "primary_conninfo" and stream WAL from there.
>
> The reason that db2 ran recovery beyond the slot LSN is the db2's
> restore_command (I guess) points to db1's archive. If db2 had its own
> archive directory or no archive (that is, restore_command is empty),
> archive recovery stops at (approximately) the slot LSN and replication
> will start from there (from the beginning of the segment, to be
> exact).
Is it a problem if archive recovery proceeds past the replication slot's LSN?
I guess I don't see the problem.
Yours,
Laurenz Albe