From 2c8a4e9be2730342cbca85150a2a9d876aa77ff6 Mon Sep 17 00:00:00 2001 From: Simon Riggs Date: Thu, 7 Jun 2012 19:22:47 +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 and often much less, allowing significantly reduced data loss at failover. Andres Freund and Simon Riggs --- src/backend/access/transam/xlog.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index d3650bdf05..0f2678cfda 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -2271,6 +2271,13 @@ XLogBackgroundFlush(void) 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(); + return wrote_something; }