Re: Synchronizing slots from primary to standby

On Mon, Nov 27, 2023 at 2:27 PM Zhijie Hou (Fujitsu)
<houzj.fnst@fujitsu.com> wrote:
>
> Here is the updated version(v39_2) which include all the changes made in 0002.
> Please use for review, and sorry for the confusion.
>

--- a/src/backend/replication/logical/launcher.c
+++ b/src/backend/replication/logical/launcher.c
@@ -8,20 +8,27 @@
  *   src/backend/replication/logical/launcher.c
  *
  * NOTES
- *   This module contains the logical replication worker launcher which
- *   uses the background worker infrastructure to start the logical
- *   replication workers for every enabled subscription.
+ *   This module contains the replication worker launcher which
+ *   uses the background worker infrastructure to:
+ *   a) start the logical replication workers for every enabled subscription
+ *      when not in standby_mode.
+ *   b) start the slot sync worker for logical failover slots synchronization
+ *      from the primary server when in standby_mode.

I was wondering do we really need a launcher on standby to invoke
sync-slot worker. If so, why? I guess it may be required for previous
versions where we were managing work for multiple slot-sync workers
which is also questionable in the sense of whether launcher is the
right candidate for the same but now with the single slot-sync worker,
it doesn't seem worth having it. What do you think?

--
With Regards,
Amit Kapila.