From 090e8a984cf1a8a3ef7f6db6dc919f843902d80c Mon Sep 17 00:00:00 2001 From: Simon Riggs Date: Thu, 7 Jun 2012 19:26:03 +0100 Subject: [PATCH] Wake WALSender to reduce data loss at failover for async commit. WALSender now woken up after each background flush by WALwriter, avoiding multi-second replication delay for an all-async commit workload. Replication delay reduced from 7s with default settings to 200ms, allowing significantly reduced data loss at failover. Andres Freund and Simon Riggs --- src/backend/access/transam/xlog.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 3902c58313..64d7660b38 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -2115,6 +2115,7 @@ XLogBackgroundFlush(void) { XLogRecPtr WriteRqstPtr; bool flexible = true; + bool wrote_something = false; /* XLOG doesn't need flushing during recovery */ if (RecoveryInProgress()) @@ -2183,10 +2184,18 @@ XLogBackgroundFlush(void) WriteRqst.Write = WriteRqstPtr; WriteRqst.Flush = WriteRqstPtr; XLogWrite(WriteRqst, flexible, false); + wrote_something = true; } LWLockRelease(WALWriteLock); END_CRIT_SECTION(); + + /* + * If we wrote something then we have something to send to standbys also, + * otherwise the replication delay become around 7s with just async commit. + */ + if (wrote_something) + WalSndWakeup(); } /* -- 2.40.0