Fix for slaves chains. Force resync of slaves (simply disconnecting them) ...

Fix for slaves chains. Force resync of slaves (simply disconnecting them)  when SLAVEOF turns a master into a slave.

src/networking.c

@@ -491,6 +491,16 @@ static void freeClientArgv(redisClient *c) {
     c->cmd = NULL;
 }
 
+/* Close all the slaves connections. This is useful in chained replication
+ * when we resync with our own master and want to force all our slaves to
+ * resync with us as well. */
+void disconnectSlaves(void) {
+    while (listLength(server.slaves)) {
+        listNode *ln = listFirst(server.slaves);
+        freeClient((redisClient*)ln->value);
+    }
+}
+
 void freeClient(redisClient *c) {
     listNode *ln;
 
@@ -568,21 +578,12 @@ void freeClient(redisClient *c) {
         server.master = NULL;
         server.replstate = REDIS_REPL_CONNECT;
         server.repl_down_since = time(NULL);
-        /* Since we lost the connection with the master, we should also
-         * close the connection with all our slaves if we have any, so
-         * when we'll resync with the master the other slaves will sync again
-         * with us as well. Note that also when the slave is not connected
-         * to the master it will keep refusing connections by other slaves.
+        /* We lost connection with our master, force our slaves to resync
+         * with us as well to load the new data set.
          *
-         * We do this only if server.masterhost != NULL. If it is NULL this
-         * means the user called SLAVEOF NO ONE and we are freeing our
-         * link with the master, so no need to close link with slaves. */
-        if (server.masterhost != NULL) {
-            while (listLength(server.slaves)) {
-                ln = listFirst(server.slaves);
-                freeClient((redisClient*)ln->value);
-            }
-        }
+         * If server.masterhost is NULL the user called SLAVEOF NO ONE so
+         * slave resync is not needed. */
+        if (server.masterhost != NULL) disconnectSlaves();
     }
     /* Release memory */
     zfree(c->argv);

src/redis.h

@@ -718,6 +718,7 @@ sds getAllClientsInfoString(void);
 void rewriteClientCommandVector(redisClient *c, int argc, ...);
 unsigned long getClientOutputBufferMemoryUsage(redisClient *c);
 void flushSlavesOutputBuffers(void);
+void disconnectSlaves(void);
 
 #ifdef __GNUC__
 void addReplyErrorFormat(redisClient *c, const char *fmt, ...)

src/replication.c

@@ -507,6 +507,7 @@ void slaveofCommand(redisClient *c) {
         server.masterhost = sdsdup(c->argv[1]->ptr);
         server.masterport = atoi(c->argv[2]->ptr);
         if (server.master) freeClient(server.master);
+        disconnectSlaves(); /* Force our slaves to resync with us as well. */
         if (server.replstate == REDIS_REPL_TRANSFER)
             replicationAbortSyncTransfer();
         server.replstate = REDIS_REPL_CONNECT;