From 32d0a79f7871052429f38c65ee0b341c7fbbe3e5 Mon Sep 17 00:00:00 2001
From: antirez <antirez@gmail.com>
Date: Sat, 7 Jun 2014 14:37:09 +0200
Subject: [PATCH] Cluster: check that configEpoch never goes back.

Since there are ways to alter the configEpoch outside of the failover
procedure (for exampel CLUSTER SET-CONFIG-EPOCH and via the configEpoch
collision resolution algorithm), make always sure, before replacing our
configEpoch with a new one, that it is greater than the current one.
---
 src/cluster.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/cluster.c b/src/cluster.c
index bdaf36fb..1193d6c6 100644
--- a/src/cluster.c
+++ b/src/cluster.c
@@ -2516,7 +2516,8 @@ void clusterHandleSlaveFailover(void) {
         }
 
         /* 3) Update my configEpoch to the epoch of the election. */
-        myself->configEpoch = server.cluster->failover_auth_epoch;
+        if (myself->configEpoch < server.cluster->failover_auth_epoch)
+            myself->configEpoch = server.cluster->failover_auth_epoch;
 
         /* 4) Update state and save config. */
         clusterUpdateState();