> On Sep 28, 2025, at 18:24, Joel Jacobson <[email protected]> wrote: > >> >> I might miss the factor of holding an exclusive lock. I will revisit >> that part again. > > I've re-read this entire thread, and I actually think my original > approaches are more promising, that is, the > 0001-optimize_listen_notify-v4.patch patch, doing multicast targeted > signaling. > > Therefore, merely consider the latest patch as PoC with some possible > interesting ideas. > > Before this patch, I had never used PostgreSQL's timeout mechanism > before, so I didn't consider it when thinking about how to solve the > remaining problems with 0001-optimize_listen_notify-v4.patch, which > currently can't guarantee that all listening backends will eventually > catch up, since it just kicks one of the most lagging ones, for each > notification. This could be a problem in practise if there is a long > period of time with no notifications coming in. Then some listening > backends could end up not being signaled and would stay behind, > preventing the queue tail from advancing. > > I'm thinking maybe somehow we can use the timeout mechanism here, but > I'm not sure how yet. Any ideas? > > /Joel
Hi Joel, I never had a concern about using the timeout mechanism. My comment was about enabling timeout duplicately. I just revisited the code, now I agree that I was over-worried because I missed considering NotifyQueueLock. With the lock protection, a backend process’ QUEUE_BACKEND_WAKEUP_PENDING_FLAG won’t have race condition, then it should have no duplicate signals sending to the same backend process. Then in the backend process, you have “last_wakeup_start_time” that avoids duplicate timeout within a configured period, and you reset last_wakeup_start_time in asyncQueueReadAllNotifications() together with cleaning the QUEUE_BACKEND_WAKEUP_PENDING_FLAG. So, overall v2 looks good to me. One last tiny comment is about naming of last_wakeup_start_time. I think it can be renamed to “last_wakeup_time”. Because the variable just records when asyncQueueReadAllNotifications() last time called, there seems not a meaning of “start” involved. Best regards, -- Chao Li (Evan) HighGo Software Co., Ltd. https://www.highgo.com/
