Re: Disallow quorum uncommitted (with synchronous standbys) txns in logical replication subscribers

On Wed, 2022-01-05 at 23:59 -0800, SATYANARAYANA NARLAPURAM wrote:
> I would like to propose a GUC send_Wal_after_quorum_committed which
> when set to ON, walsenders corresponds to async standbys and logical
> replication workers wait until the LSN is quorum committed on the
> primary before sending it to the standby. This not only simplifies
> the post failover steps but avoids unnecessary downtime for the async
> replicas. Thoughts?

Do we need a GUC? Or should we just always require that sync rep is
satisfied before sending to async replicas?

It feels like the sync quorum should always be ahead of the async
replicas. Unless I'm missing a use case, or there is some kind of
performance gotcha.

Regards,
    Jeff Davis