postgres.git / summary / log / commit / refs

commit    090e8a984cf1a8a3ef7f6db6dc919f843902d80c
Author:   Simon Riggs <simon@2ndQuadrant.com>
Date:     Thu Jun 07 18:26:03 2012 +0000
First released in: 9.2.0, REL9_0_STABLE (reverted before release), 9.1.5
Reverted by: da6bb58ed9da (in 9.0.9)

    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 3902c583134..64d7660b38b 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();
 }
 
 /*


[parent: 110ebff20972]