Hi, On Thu, Apr 04, 2024 at 05:31:45PM +0530, shveta malik wrote: > On Thu, Apr 4, 2024 at 2:59 PM shveta malik <shveta.ma...@gmail.com> wrote: > > > > > > Prior to commit 2ec005b, this check was okay, as we did not expect > > restart_lsn of the synced slot to be ahead of remote since we were > > directly copying the lsns. But now when we use 'advance' to do logical > > decoding on standby, there is a possibility that restart lsn of the > > synced slot is ahead of remote slot, if there are running txns records > > found after reaching consistent-point while consuming WALs from > > restart_lsn till confirmed_lsn. In such a case, slot-sync's advance > > may end up serializing snapshots and setting restart_lsn to the > > serialized snapshot point, ahead of remote one. > > > > Fix: > > The sanity check needs to be corrected. Attached a patch to address the > > issue. >
Thanks for reporting, explaining the issue and providing a patch. Regarding the patch: 1 === + * Attempt to sync lsns and xmins only if remote slot is ahead of local s/lsns/LSNs/? 2 === + if (slot->data.confirmed_flush != remote_slot->confirmed_lsn) + elog(LOG, + "could not synchronize local slot \"%s\" LSN(%X/%X)" + " to remote slot's LSN(%X/%X) ", + remote_slot->name, + LSN_FORMAT_ARGS(slot->data.confirmed_flush), + LSN_FORMAT_ARGS(remote_slot->confirmed_lsn)); I don't think that the message is correct here. Unless I am missing something there is nothing in the following code path that would prevent the slot to be sync during this cycle. Regards, -- Bertrand Drouvot PostgreSQL Contributors Team RDS Open Source Databases Amazon Web Services: https://aws.amazon.com