ROLE command added.

The new ROLE command is designed in order to provide a client with
informations about the replication in a fast and easy to use way
compared to the INFO command where the same information is also
available.

src/redis.c

@@ -243,6 +243,7 @@ struct redisCommand redisCommandTable[] = {
     {"pttl",pttlCommand,2,"r",0,NULL,1,1,1,0,0},
     {"persist",persistCommand,2,"w",0,NULL,1,1,1,0,0},
     {"slaveof",slaveofCommand,3,"ast",0,NULL,0,0,0,0,0},
+    {"role",roleCommand,1,"ast",0,NULL,0,0,0,0,0},
     {"debug",debugCommand,-2,"as",0,NULL,0,0,0,0,0},
     {"config",configCommand,-2,"art",0,NULL,0,0,0,0,0},
     {"subscribe",subscribeCommand,-2,"rpslt",0,NULL,0,0,0,0,0},

src/redis.h

@@ -1394,6 +1394,7 @@ void ttlCommand(redisClient *c);
 void pttlCommand(redisClient *c);
 void persistCommand(redisClient *c);
 void slaveofCommand(redisClient *c);
+void roleCommand(redisClient *c);
 void debugCommand(redisClient *c);
 void msetCommand(redisClient *c);
 void msetnxCommand(redisClient *c);

src/replication.c

@@ -1324,6 +1324,43 @@ void slaveofCommand(redisClient *c) {
     addReply(c,shared.ok);
 }
 
+/* ROLE command: provide information about the role of the instance
+ * (master or slave) and additional information related to replication
+ * in an easy to process format. */
+void roleCommand(redisClient *c) {
+    if (server.masterhost == NULL) {
+        listIter li;
+        listNode *ln;
+        void *mbcount;
+        int slaves = 0;
+
+        addReplyMultiBulkLen(c,3);
+        addReplyBulkCBuffer(c,"master",6);
+        addReplyLongLong(c,server.master_repl_offset);
+        mbcount = addDeferredMultiBulkLength(c);
+        listRewind(server.slaves,&li);
+        while((ln = listNext(&li))) {
+            redisClient *slave = ln->value;
+            char ip[REDIS_IP_STR_LEN];
+
+            if (anetPeerToString(slave->fd,ip,sizeof(ip),NULL) == -1) continue;
+            if (slave->replstate != REDIS_REPL_ONLINE) continue;
+            addReplyMultiBulkLen(c,3);
+            addReplyBulkCString(c,ip);
+            addReplyBulkLongLong(c,slave->slave_listening_port);
+            addReplyBulkLongLong(c,slave->repl_ack_off);
+            slaves++;
+        }
+        setDeferredMultiBulkLength(c,mbcount,slaves);
+    } else {
+        addReplyMultiBulkLen(c,4);
+        addReplyBulkCBuffer(c,"slave",5);
+        addReplyBulkCString(c,server.masterhost);
+        addReplyLongLong(c,server.masterport);
+        addReplyLongLong(c,server.master->reploff);
+    }
+}
+
 /* Send a REPLCONF ACK command to the master to inform it about the current
  * processed offset. If we are not connected with a master, the command has
  * no effects. */