From ed0cfc31f3e84a94fc5810409ce552c3f34ceebb Mon Sep 17 00:00:00 2001
From: antirez <antirez@gmail.com>
Date: Wed, 15 Jan 2014 16:50:45 +0100
Subject: [PATCH] Cluster: use the node blacklist in CLUSTER FORGET.

CLUSTER FORGET is not useful if we can't remove a node from all the
nodes of our cluster because of the Gossip protocol that keeps adding
a given node to nodes where we already tried to remove it.

So now CLUSTER FORGET implements a nodes blacklist that is set and
checked by the Gossip section processing function. This way before a
node is re-added at least 60 seconds must elapse since the FORGET
execution.

This means that redis-trib has some time to remove a node from a whole
cluster. It is possible that in the future it will be uesful to raise
the 60 sec figure to something bigger.
---
 src/cluster.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/cluster.c b/src/cluster.c
index d6c7baa1e..e5081936f 100644
--- a/src/cluster.c
+++ b/src/cluster.c
@@ -967,8 +967,12 @@ void clusterProcessGossipSection(clusterMsg *hdr, clusterLink *link) {
              * Note that we require that the sender of this gossip message
              * is a well known node in our cluster, otherwise we risk
              * joining another cluster. */
-            if (sender && !(flags & REDIS_NODE_NOADDR))
+            if (sender &&
+                !(flags & REDIS_NODE_NOADDR) &&
+                !clusterBlacklistExists(g->nodename))
+            {
                 clusterStartHandshake(g->ip,ntohs(g->port));
+            }
         }
 
         /* Next node */
@@ -2875,6 +2879,7 @@ void clusterCommand(redisClient *c) {
             addReplyErrorFormat(c,"Unknown node %s", (char*)c->argv[2]->ptr);
             return;
         }
+        clusterBlacklistAddNode(n);
         clusterDelNode(n);
         clusterDoBeforeSleep(CLUSTER_TODO_UPDATE_STATE|CLUSTER_TODO_SAVE_CONFIG);
         addReply(c,shared.ok);