Re: Allow logical failover slots to wait on synchronous replication

On Mon, Jun 10, 2024 at 03:51:05PM -0700, John H wrote:
> The existing 'standby_slot_names' isn't great for users who are running
> clusters with quorum-based synchronous replicas. For instance, if
> the user has  synchronous_standby_names = 'ANY 3 (A,B,C,D,E)' it's a
> bit tedious to have to reconfigure the standby_slot_names to set it to
> the most updated 3 sync replicas whenever different sync replicas start
> lagging. In the event that both GUCs are set, 'standby_slot_names' takes
> precedence.

Hm.  IIUC you'd essentially need to set standby_slot_names to "A,B,C,D,E"
to get the desired behavior today.  That might ordinarily be okay, but it
could cause logical replication to be held back unnecessarily if one of the
replicas falls behind for whatever reason.  A way to tie standby_slot_names
to synchronous replication instead does seem like it would be useful in
this case.

-- 
nathan