At Thu, 22 Dec 2022 17:29:34 +0530, Ashutosh Bapat <ashutosh.bapat....@gmail.com> wrote in > On Thu, Dec 22, 2022 at 11:16 AM Hayato Kuroda (Fujitsu) > <kuroda.hay...@fujitsu.com> wrote: > > In case of logical replication, however, we cannot support the use-case that > > switches the role publisher <-> subscriber. Suppose same case as above, > > additional .. > > Therefore, I think that we can ignore the condition for shutting down the > > walsender in logical replication. ... > > This change may be useful for time-delayed logical replication. The > > walsender > > waits the shutdown until all changes are applied on subscriber, even if it > > is > > delayed. This causes that publisher cannot be stopped if large delay-time is > > specified. > > I think the current behaviour is an artifact of using the same WAL > sender code for both logical and physical replication.
Yeah, I don't think we do that for the reason of switchover. On the other hand I think the behavior was intentionally taken over since it is thought as sensible alone. And I'm afraind that many people already relies on that behavior. > I agree with you that the logical WAL sender need not wait for all the > WAL to be replayed downstream. Thus I feel that it might be a bit outrageous to get rid of that bahavior altogether because of a new feature stumbling on it. I'm fine doing that only in the apply_delay case, though. However, I have another concern that we are introducing the second exception for XLogSendLogical in the common path. I doubt that anyone wants to use synchronous logical replication with apply_delay since the sender transaction is inevitablly affected back by that delay. Thus how about before entering an apply_delay, logrep worker sending a kind of crafted feedback, which reports commit_data.end_lsn as flushpos? A little tweak is needed in send_feedback() but seems to work.. regards. -- Kyotaro Horiguchi NTT Open Source Software Center
