At Fri, 19 Aug 2022 18:37:53 +0200, Laurenz Albe <laurenz.a...@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). regards. -- Kyotaro Horiguchi NTT Open Source Software Center
