From 698b13005e6fb85741b758d9f8b14065f6394092 Mon Sep 17 00:00:00 2001 From: Alexey Makhmutov Date: Thu, 22 May 2025 04:02:50 +0300 Subject: [PATCH] Use only replayed position as target flush point for logical replication For physical walsender the GetStandbyFlushRecPtr function returns position of the latest stored WAL record, as we can stream data to downstream instance without waiting for it being locally applied. However, for logical replication we can sent data to downstream client only up to the locally applied position. This distinction is important when we decide whether walsender has sent all the available data to client ('caught up'). During the shutdown process walsender backends are allowed to work until they reach the 'caught up' state, while recovery process is already deactivated, so the applied position won't be moving. In this case walsender for logical replication should work only until it caught up with the latest applied record, otherwise it will stuck in the infinite loop and inhibit instance shutdown. --- src/backend/replication/walsender.c | 31 ++++++++++++++++------------- 1 file changed, 17 insertions(+), 14 deletions(-) diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c index 9fa8beb6103..ede985da216 100644 --- a/src/backend/replication/walsender.c +++ b/src/backend/replication/walsender.c @@ -3532,29 +3532,32 @@ WalSndDone(WalSndSendDataCallback send_data) XLogRecPtr GetStandbyFlushRecPtr(TimeLineID *tli) { - XLogRecPtr replayPtr; TimeLineID replayTLI; - XLogRecPtr receivePtr; - TimeLineID receiveTLI; XLogRecPtr result; Assert(am_cascading_walsender || IsSyncingReplicationSlots()); - /* - * We can safely send what's already been replayed. Also, if walreceiver - * is streaming WAL from the same timeline, we can send anything that it - * has streamed, but hasn't been replayed yet. - */ - - receivePtr = GetWalRcvFlushRecPtr(NULL, &receiveTLI); - replayPtr = GetXLogReplayRecPtr(&replayTLI); + result = GetXLogReplayRecPtr(&replayTLI); if (tli) *tli = replayTLI; - result = replayPtr; - if (receiveTLI == replayTLI && receivePtr > replayPtr) - result = receivePtr; + /* + * We can safely send what's already been replayed. Also, for physical + * replication if walreceiver is streaming WAL from the same timeline, we + * can send anything that it has streamed, but hasn't been replayed yet. + * If this function is called from slot synchronization (MyWalSnd is NULL + * in this case), then we should follow physical replication approach as + * well to be consistent with synchronized_standby_slots expectations. + */ + if (!MyWalSnd || MyWalSnd->kind == REPLICATION_KIND_PHYSICAL) + { + TimeLineID receiveTLI; + XLogRecPtr receivePtr = GetWalRcvFlushRecPtr(NULL, &receiveTLI); + + if (receiveTLI == replayTLI && receivePtr > result) + result = receivePtr; + } return result; } -- 2.49.0