X-Git-Url: https://git.saurik.com/redis.git/blobdiff_plain/e394114d95395fe9babb0a658de263a0811ec330..d310fbedabd3101505b694f5c25a2e48480a3c2b:/src/replication.c?ds=sidebyside

diff --git a/src/replication.c b/src/replication.c
index d671acc2..871ce95a 100644
--- a/src/replication.c
+++ b/src/replication.c
@@ -3,6 +3,7 @@
 #include <sys/time.h>
 #include <unistd.h>
 #include <fcntl.h>
+#include <sys/socket.h>
 #include <sys/stat.h>
 
 /* ---------------------------------- MASTER -------------------------------- */
@@ -25,24 +26,15 @@ void replicationFeedSlaves(list *slaves, int dictid, robj **argv, int argc) {
         if (slave->slaveseldb != dictid) {
             robj *selectcmd;
 
-            switch(dictid) {
-            case 0: selectcmd = shared.select0; break;
-            case 1: selectcmd = shared.select1; break;
-            case 2: selectcmd = shared.select2; break;
-            case 3: selectcmd = shared.select3; break;
-            case 4: selectcmd = shared.select4; break;
-            case 5: selectcmd = shared.select5; break;
-            case 6: selectcmd = shared.select6; break;
-            case 7: selectcmd = shared.select7; break;
-            case 8: selectcmd = shared.select8; break;
-            case 9: selectcmd = shared.select9; break;
-            default:
+            if (dictid >= 0 && dictid < REDIS_SHARED_SELECT_CMDS) {
+                selectcmd = shared.select[dictid];
+                incrRefCount(selectcmd);
+            } else {
                 selectcmd = createObject(REDIS_STRING,
                     sdscatprintf(sdsempty(),"select %d\r\n",dictid));
-                selectcmd->refcount = 0;
-                break;
             }
             addReply(slave,selectcmd);
+            decrRefCount(selectcmd);
             slave->slaveseldb = dictid;
         }
         addReplyMultiBulkLen(slave,argc);
@@ -50,17 +42,23 @@ void replicationFeedSlaves(list *slaves, int dictid, robj **argv, int argc) {
     }
 }
 
-void replicationFeedMonitors(list *monitors, int dictid, robj **argv, int argc) {
+void replicationFeedMonitors(redisClient *c, list *monitors, int dictid, robj **argv, int argc) {
     listNode *ln;
     listIter li;
-    int j;
+    int j, port;
     sds cmdrepr = sdsnew("+");
     robj *cmdobj;
+    char ip[32];
     struct timeval tv;
 
     gettimeofday(&tv,NULL);
     cmdrepr = sdscatprintf(cmdrepr,"%ld.%06ld ",(long)tv.tv_sec,(long)tv.tv_usec);
-    if (dictid != 0) cmdrepr = sdscatprintf(cmdrepr,"(db %d) ", dictid);
+    if (c->flags & REDIS_LUA_CLIENT) {
+        cmdrepr = sdscatprintf(cmdrepr,"[%d lua] ", dictid);
+    } else {
+        anetPeerToString(c->fd,ip,&port);
+        cmdrepr = sdscatprintf(cmdrepr,"[%d %s:%d] ", dictid,ip,port);
+    }
 
     for (j = 0; j < argc; j++) {
         if (argv[j]->encoding == REDIS_ENCODING_INT) {
@@ -89,7 +87,7 @@ void syncCommand(redisClient *c) {
 
     /* Refuse SYNC requests if we are a slave but the link with our master
      * is not ok... */
-    if (server.masterhost && server.replstate != REDIS_REPL_CONNECTED) {
+    if (server.masterhost && server.repl_state != REDIS_REPL_CONNECTED) {
         addReplyError(c,"Can't SYNC while not connected with my master");
         return;
     }
@@ -106,7 +104,7 @@ void syncCommand(redisClient *c) {
     redisLog(REDIS_NOTICE,"Slave ask for synchronization");
     /* Here we need to check if there is a background saving operation
      * in progress, or if it is required to start one */
-    if (server.bgsavechildpid != -1) {
+    if (server.rdb_child_pid != -1) {
         /* Ok a background save is in progress. Let's check if it is a good
          * one for replication, i.e. if there is another slave that is
          * registering differences since the server forked to save */
@@ -122,8 +120,7 @@ void syncCommand(redisClient *c) {
         if (ln) {
             /* Perfect, the server is already registering differences for
              * another slave. Set the right state, and copy the buffer. */
-            listRelease(c->reply);
-            c->reply = listDup(slave->reply);
+            copyClientOutputBuffer(c,slave);
             c->replstate = REDIS_REPL_WAIT_BGSAVE_END;
             redisLog(REDIS_NOTICE,"Waiting for end of BGSAVE for SYNC");
         } else {
@@ -135,7 +132,7 @@ void syncCommand(redisClient *c) {
     } else {
         /* Ok we don't have a BGSAVE in progress, let's start one */
         redisLog(REDIS_NOTICE,"Starting BGSAVE for SYNC");
-        if (rdbSaveBackground(server.dbfilename) != REDIS_OK) {
+        if (rdbSaveBackground(server.rdb_filename) != REDIS_OK) {
             redisLog(REDIS_NOTICE,"Replication failed, can't BGSAVE");
             addReplyError(c,"Unable to perform background save");
             return;
@@ -149,6 +146,46 @@ void syncCommand(redisClient *c) {
     return;
 }
 
+/* REPLCONF <option> <value> <option> <value> ...
+ * This command is used by a slave in order to configure the replication
+ * process before starting it with the SYNC command.
+ *
+ * Currently the only use of this command is to communicate to the master
+ * what is the listening port of the Slave redis instance, so that the
+ * master can accurately list slaves and their listening ports in
+ * the INFO output.
+ *
+ * In the future the same command can be used in order to configure
+ * the replication to initiate an incremental replication instead of a
+ * full resync. */
+void replconfCommand(redisClient *c) {
+    int j;
+
+    if ((c->argc % 2) == 0) {
+        /* Number of arguments must be odd to make sure that every
+         * option has a corresponding value. */
+        addReply(c,shared.syntaxerr);
+        return;
+    }
+
+    /* Process every option-value pair. */
+    for (j = 1; j < c->argc; j+=2) {
+        if (!strcasecmp(c->argv[j]->ptr,"listening-port")) {
+            long port;
+
+            if ((getLongFromObjectOrReply(c,c->argv[j+1],
+                    &port,NULL) != REDIS_OK))
+                return;
+            c->slave_listening_port = port;
+        } else {
+            addReplyErrorFormat(c,"Unrecognized REPLCONF option: %s",
+                (char*)c->argv[j]->ptr);
+            return;
+        }
+    }
+    addReply(c,shared.ok);
+}
+
 void sendBulkToSlave(aeEventLoop *el, int fd, void *privdata, int mask) {
     redisClient *slave = privdata;
     REDIS_NOTUSED(el);
@@ -198,7 +235,6 @@ void sendBulkToSlave(aeEventLoop *el, int fd, void *privdata, int mask) {
             freeClient(slave);
             return;
         }
-        addReplySds(slave,sdsempty());
         redisLog(REDIS_NOTICE,"Synchronization with slave succeeded");
     }
 }
@@ -229,7 +265,7 @@ void updateSlavesWaitingBgsave(int bgsaveerr) {
                 redisLog(REDIS_WARNING,"SYNC failed. BGSAVE child returned an error");
                 continue;
             }
-            if ((slave->repldbfd = open(server.dbfilename,O_RDONLY)) == -1 ||
+            if ((slave->repldbfd = open(server.rdb_filename,O_RDONLY)) == -1 ||
                 redis_fstat(slave->repldbfd,&buf) == -1) {
                 freeClient(slave);
                 redisLog(REDIS_WARNING,"SYNC failed. Can't open/stat DB after BGSAVE: %s", strerror(errno));
@@ -246,7 +282,7 @@ void updateSlavesWaitingBgsave(int bgsaveerr) {
         }
     }
     if (startbgsave) {
-        if (rdbSaveBackground(server.dbfilename) != REDIS_OK) {
+        if (rdbSaveBackground(server.rdb_filename) != REDIS_OK) {
             listIter li;
 
             listRewind(server.slaves,&li);
@@ -265,28 +301,30 @@ void updateSlavesWaitingBgsave(int bgsaveerr) {
 
 /* Abort the async download of the bulk dataset while SYNC-ing with master */
 void replicationAbortSyncTransfer(void) {
-    redisAssert(server.replstate == REDIS_REPL_TRANSFER);
+    redisAssert(server.repl_state == REDIS_REPL_TRANSFER);
 
     aeDeleteFileEvent(server.el,server.repl_transfer_s,AE_READABLE);
     close(server.repl_transfer_s);
     close(server.repl_transfer_fd);
     unlink(server.repl_transfer_tmpfile);
     zfree(server.repl_transfer_tmpfile);
-    server.replstate = REDIS_REPL_CONNECT;
+    server.repl_state = REDIS_REPL_CONNECT;
 }
 
 /* Asynchronously read the SYNC payload we receive from a master */
+#define REPL_MAX_WRITTEN_BEFORE_FSYNC (1024*1024*8) /* 8 MB */
 void readSyncBulkPayload(aeEventLoop *el, int fd, void *privdata, int mask) {
     char buf[4096];
     ssize_t nread, readlen;
+    off_t left;
     REDIS_NOTUSED(el);
     REDIS_NOTUSED(privdata);
     REDIS_NOTUSED(mask);
 
-    /* If repl_transfer_left == -1 we still have to read the bulk length
+    /* If repl_transfer_size == -1 we still have to read the bulk length
      * from the master reply. */
-    if (server.repl_transfer_left == -1) {
-        if (syncReadLine(fd,buf,1024,server.repl_syncio_timeout) == -1) {
+    if (server.repl_transfer_size == -1) {
+        if (syncReadLine(fd,buf,1024,server.repl_syncio_timeout*1000) == -1) {
             redisLog(REDIS_WARNING,
                 "I/O error reading bulk count from MASTER: %s",
                 strerror(errno));
@@ -302,22 +340,22 @@ void readSyncBulkPayload(aeEventLoop *el, int fd, void *privdata, int mask) {
             /* At this stage just a newline works as a PING in order to take
              * the connection live. So we refresh our last interaction
              * timestamp. */
-            server.repl_transfer_lastio = time(NULL);
+            server.repl_transfer_lastio = server.unixtime;
             return;
         } else if (buf[0] != '$') {
             redisLog(REDIS_WARNING,"Bad protocol from MASTER, the first byte is not '$', are you sure the host and port are right?");
             goto error;
         }
-        server.repl_transfer_left = strtol(buf+1,NULL,10);
+        server.repl_transfer_size = strtol(buf+1,NULL,10);
         redisLog(REDIS_NOTICE,
             "MASTER <-> SLAVE sync: receiving %ld bytes from master",
-            server.repl_transfer_left);
+            server.repl_transfer_size);
         return;
     }
 
     /* Read bulk data */
-    readlen = (server.repl_transfer_left < (signed)sizeof(buf)) ?
-        server.repl_transfer_left : (signed)sizeof(buf);
+    left = server.repl_transfer_size - server.repl_transfer_read;
+    readlen = (left < (signed)sizeof(buf)) ? left : (signed)sizeof(buf);
     nread = read(fd,buf,readlen);
     if (nread <= 0) {
         redisLog(REDIS_WARNING,"I/O error trying to sync with MASTER: %s",
@@ -325,15 +363,29 @@ void readSyncBulkPayload(aeEventLoop *el, int fd, void *privdata, int mask) {
         replicationAbortSyncTransfer();
         return;
     }
-    server.repl_transfer_lastio = time(NULL);
+    server.repl_transfer_lastio = server.unixtime;
     if (write(server.repl_transfer_fd,buf,nread) != nread) {
-        redisLog(REDIS_WARNING,"Write error or short write writing to the DB dump file needed for MASTER <-> SLAVE synchrnonization: %s", strerror(errno));
+        redisLog(REDIS_WARNING,"Write error or short write writing to the DB dump file needed for MASTER <-> SLAVE synchronization: %s", strerror(errno));
         goto error;
     }
-    server.repl_transfer_left -= nread;
+    server.repl_transfer_read += nread;
+
+    /* Sync data on disk from time to time, otherwise at the end of the transfer
+     * we may suffer a big delay as the memory buffers are copied into the
+     * actual disk. */
+    if (server.repl_transfer_read >=
+        server.repl_transfer_last_fsync_off + REPL_MAX_WRITTEN_BEFORE_FSYNC)
+    {
+        off_t sync_size = server.repl_transfer_read -
+                          server.repl_transfer_last_fsync_off;
+        rdb_fsync_range(server.repl_transfer_fd,
+            server.repl_transfer_last_fsync_off, sync_size);
+        server.repl_transfer_last_fsync_off += sync_size;
+    }
+
     /* Check if the transfer is now complete */
-    if (server.repl_transfer_left == 0) {
-        if (rename(server.repl_transfer_tmpfile,server.dbfilename) == -1) {
+    if (server.repl_transfer_read == server.repl_transfer_size) {
+        if (rename(server.repl_transfer_tmpfile,server.rdb_filename) == -1) {
             redisLog(REDIS_WARNING,"Failed trying to rename the temp DB into dump.rdb in MASTER <-> SLAVE synchronization: %s", strerror(errno));
             replicationAbortSyncTransfer();
             return;
@@ -345,7 +397,7 @@ void readSyncBulkPayload(aeEventLoop *el, int fd, void *privdata, int mask) {
          * rdbLoad() will call the event loop to process events from time to
          * time for non blocking loading. */
         aeDeleteFileEvent(server.el,server.repl_transfer_s,AE_READABLE);
-        if (rdbLoad(server.dbfilename) != REDIS_OK) {
+        if (rdbLoad(server.rdb_filename) != REDIS_OK) {
             redisLog(REDIS_WARNING,"Failed trying to load the MASTER synchronization DB from disk");
             replicationAbortSyncTransfer();
             return;
@@ -356,7 +408,7 @@ void readSyncBulkPayload(aeEventLoop *el, int fd, void *privdata, int mask) {
         server.master = createClient(server.repl_transfer_s);
         server.master->flags |= REDIS_MASTER;
         server.master->authenticated = 1;
-        server.replstate = REDIS_REPL_CONNECTED;
+        server.repl_state = REDIS_REPL_CONNECTED;
         redisLog(REDIS_NOTICE, "MASTER <-> SLAVE sync: Finished with success");
         /* Restart the AOF subsystem now that we finished the sync. This
          * will trigger an AOF rewrite, and when done will start appending
@@ -383,51 +435,152 @@ error:
     return;
 }
 
+/* Send a synchronous command to the master. Used to send AUTH and
+ * REPLCONF commands before starting the replication with SYNC.
+ *
+ * On success NULL is returned.
+ * On error an sds string describing the error is returned.
+ */
+char *sendSynchronousCommand(int fd, ...) {
+    va_list ap;
+    sds cmd = sdsempty();
+    char *arg, buf[256];
+
+    /* Create the command to send to the master, we use simple inline
+     * protocol for simplicity as currently we only send simple strings. */
+    va_start(ap,fd);
+    while(1) {
+        arg = va_arg(ap, char*);
+        if (arg == NULL) break;
+
+        if (sdslen(cmd) != 0) cmd = sdscatlen(cmd," ",1);
+        cmd = sdscat(cmd,arg);
+    }
+    cmd = sdscatlen(cmd,"\r\n",2);
+
+    /* Transfer command to the server. */
+    if (syncWrite(fd,cmd,sdslen(cmd),server.repl_syncio_timeout*1000) == -1) {
+        sdsfree(cmd);
+        return sdscatprintf(sdsempty(),"Writing to master: %s",
+                strerror(errno));
+    }
+    sdsfree(cmd);
+
+    /* Read the reply from the server. */
+    if (syncReadLine(fd,buf,sizeof(buf),server.repl_syncio_timeout*1000) == -1)
+    {
+        return sdscatprintf(sdsempty(),"Reading from master: %s",
+                strerror(errno));
+    }
+
+    /* Check for errors from the server. */
+    if (buf[0] != '+') {
+        return sdscatprintf(sdsempty(),"Error from master: %s", buf);
+    }
+
+    return NULL; /* No errors. */
+}
+
 void syncWithMaster(aeEventLoop *el, int fd, void *privdata, int mask) {
-    char buf[1024], tmpfile[256];
+    char tmpfile[256], *err;
     int dfd, maxtries = 5;
+    int sockerr = 0;
+    socklen_t errlen = sizeof(sockerr);
     REDIS_NOTUSED(el);
     REDIS_NOTUSED(privdata);
     REDIS_NOTUSED(mask);
 
     /* If this event fired after the user turned the instance into a master
      * with SLAVEOF NO ONE we must just return ASAP. */
-    if (server.replstate == REDIS_REPL_NONE) {
+    if (server.repl_state == REDIS_REPL_NONE) {
         close(fd);
         return;
     }
 
-    redisLog(REDIS_NOTICE,"Non blocking connect for SYNC fired the event.");
-    /* This event should only be triggered once since it is used to have a
-     * non-blocking connect(2) to the master. It has been triggered when this
-     * function is called, so we can delete it. */
-    aeDeleteFileEvent(server.el,fd,AE_READABLE|AE_WRITABLE);
+    /* Check for errors in the socket. */
+    if (getsockopt(fd, SOL_SOCKET, SO_ERROR, &sockerr, &errlen) == -1)
+        sockerr = errno;
+    if (sockerr) {
+        aeDeleteFileEvent(server.el,fd,AE_READABLE|AE_WRITABLE);
+        redisLog(REDIS_WARNING,"Error condition on socket for SYNC: %s",
+            strerror(sockerr));
+        goto error;
+    }
 
-    /* AUTH with the master if required. */
-    if(server.masterauth) {
-        char authcmd[1024];
-        size_t authlen;
+    /* If we were connecting, it's time to send a non blocking PING, we want to
+     * make sure the master is able to reply before going into the actual
+     * replication process where we have long timeouts in the order of
+     * seconds (in the meantime the slave would block). */
+    if (server.repl_state == REDIS_REPL_CONNECTING) {
+        redisLog(REDIS_NOTICE,"Non blocking connect for SYNC fired the event.");
+        /* Delete the writable event so that the readable event remains
+         * registered and we can wait for the PONG reply. */
+        aeDeleteFileEvent(server.el,fd,AE_WRITABLE);
+        server.repl_state = REDIS_REPL_RECEIVE_PONG;
+        /* Send the PING, don't check for errors at all, we have the timeout
+         * that will take care about this. */
+        syncWrite(fd,"PING\r\n",6,100);
+        return;
+    }
+
+    /* Receive the PONG command. */
+    if (server.repl_state == REDIS_REPL_RECEIVE_PONG) {
+        char buf[1024];
 
-        authlen = snprintf(authcmd,sizeof(authcmd),"AUTH %s\r\n",server.masterauth);
-        if (syncWrite(fd,authcmd,authlen,server.repl_syncio_timeout) == -1) {
-            redisLog(REDIS_WARNING,"Unable to AUTH to MASTER: %s",
+        /* Delete the readable event, we no longer need it now that there is
+         * the PING reply to read. */
+        aeDeleteFileEvent(server.el,fd,AE_READABLE);
+
+        /* Read the reply with explicit timeout. */
+        buf[0] = '\0';
+        if (syncReadLine(fd,buf,sizeof(buf),
+            server.repl_syncio_timeout*1000) == -1)
+        {
+            redisLog(REDIS_WARNING,
+                "I/O error reading PING reply from master: %s",
                 strerror(errno));
             goto error;
         }
-        /* Read the AUTH result.  */
-        if (syncReadLine(fd,buf,1024,server.repl_syncio_timeout) == -1) {
-            redisLog(REDIS_WARNING,"I/O error reading auth result from MASTER: %s",
-                strerror(errno));
+
+        /* We don't care about the reply, it can be +PONG or an error since
+         * the server requires AUTH. As long as it replies correctly, it's
+         * fine from our point of view. */
+        if (buf[0] != '-' && buf[0] != '+') {
+            redisLog(REDIS_WARNING,"Unexpected reply to PING from master.");
             goto error;
+        } else {
+            redisLog(REDIS_NOTICE,
+                "Master replied to PING, replication can continue...");
         }
-        if (buf[0] != '+') {
-            redisLog(REDIS_WARNING,"Cannot AUTH to MASTER, is the masterauth password correct?");
+    }
+
+    /* AUTH with the master if required. */
+    if(server.masterauth) {
+        err = sendSynchronousCommand(fd,"AUTH",server.masterauth,NULL);
+        if (err) {
+            redisLog(REDIS_WARNING,"Unable to AUTH to MASTER: %s",err);
+            sdsfree(err);
             goto error;
         }
     }
 
+    /* Set the slave port, so that Master's INFO command can list the
+     * slave listening port correctly. */
+    {
+        sds port = sdsfromlonglong(server.port);
+        err = sendSynchronousCommand(fd,"REPLCONF","listening-port",port,
+                                         NULL);
+        sdsfree(port);
+        /* Ignore the error if any, not all the Redis versions support
+         * REPLCONF listening-port. */
+        if (err) {
+            redisLog(REDIS_NOTICE,"(non critical): Master does not understand REPLCONF listening-port: %s", err);
+            sdsfree(err);
+        }
+    }
+
     /* Issue the SYNC command */
-    if (syncWrite(fd,"SYNC \r\n",7,server.repl_syncio_timeout) == -1) {
+    if (syncWrite(fd,"SYNC\r\n",6,server.repl_syncio_timeout*1000) == -1) {
         redisLog(REDIS_WARNING,"I/O error writing to MASTER: %s",
             strerror(errno));
         goto error;
@@ -436,7 +589,7 @@ void syncWithMaster(aeEventLoop *el, int fd, void *privdata, int mask) {
     /* Prepare a suitable temp file for bulk transfer */
     while(maxtries--) {
         snprintf(tmpfile,256,
-            "temp-%d.%ld.rdb",(int)time(NULL),(long int)getpid());
+            "temp-%d.%ld.rdb",(int)server.unixtime,(long int)getpid());
         dfd = open(tmpfile,O_CREAT|O_WRONLY|O_EXCL,0644);
         if (dfd != -1) break;
         sleep(1);
@@ -454,16 +607,19 @@ void syncWithMaster(aeEventLoop *el, int fd, void *privdata, int mask) {
         goto error;
     }
 
-    server.replstate = REDIS_REPL_TRANSFER;
-    server.repl_transfer_left = -1;
+    server.repl_state = REDIS_REPL_TRANSFER;
+    server.repl_transfer_size = -1;
+    server.repl_transfer_read = 0;
+    server.repl_transfer_last_fsync_off = 0;
     server.repl_transfer_fd = dfd;
-    server.repl_transfer_lastio = time(NULL);
+    server.repl_transfer_lastio = server.unixtime;
     server.repl_transfer_tmpfile = zstrdup(tmpfile);
     return;
 
 error:
-    server.replstate = REDIS_REPL_CONNECT;
     close(fd);
+    server.repl_transfer_s = -1;
+    server.repl_state = REDIS_REPL_CONNECT;
     return;
 }
 
@@ -485,9 +641,9 @@ int connectWithMaster(void) {
         return REDIS_ERR;
     }
 
-    server.repl_transfer_lastio = time(NULL);
+    server.repl_transfer_lastio = server.unixtime;
     server.repl_transfer_s = fd;
-    server.replstate = REDIS_REPL_CONNECTING;
+    server.repl_state = REDIS_REPL_CONNECTING;
     return REDIS_OK;
 }
 
@@ -496,11 +652,12 @@ int connectWithMaster(void) {
 void undoConnectWithMaster(void) {
     int fd = server.repl_transfer_s;
 
-    redisAssert(server.replstate == REDIS_REPL_CONNECTING);
+    redisAssert(server.repl_state == REDIS_REPL_CONNECTING ||
+                server.repl_state == REDIS_REPL_RECEIVE_PONG);
     aeDeleteFileEvent(server.el,fd,AE_READABLE|AE_WRITABLE);
     close(fd);
     server.repl_transfer_s = -1;
-    server.replstate = REDIS_REPL_CONNECT;
+    server.repl_state = REDIS_REPL_CONNECT;
 }
 
 void slaveofCommand(redisClient *c) {
@@ -510,21 +667,37 @@ void slaveofCommand(redisClient *c) {
             sdsfree(server.masterhost);
             server.masterhost = NULL;
             if (server.master) freeClient(server.master);
-            if (server.replstate == REDIS_REPL_TRANSFER)
+            if (server.repl_state == REDIS_REPL_TRANSFER)
                 replicationAbortSyncTransfer();
-            else if (server.replstate == REDIS_REPL_CONNECTING)
+            else if (server.repl_state == REDIS_REPL_CONNECTING ||
+                     server.repl_state == REDIS_REPL_RECEIVE_PONG)
                 undoConnectWithMaster();
-            server.replstate = REDIS_REPL_NONE;
+            server.repl_state = REDIS_REPL_NONE;
             redisLog(REDIS_NOTICE,"MASTER MODE enabled (user request)");
         }
     } else {
+        long port;
+
+        if ((getLongFromObjectOrReply(c, c->argv[2], &port, NULL) != REDIS_OK))
+            return;
+
+        /* Check if we are already attached to the specified slave */
+        if (server.masterhost && !strcasecmp(server.masterhost,c->argv[1]->ptr)
+            && server.masterport == port) {
+            redisLog(REDIS_NOTICE,"SLAVE OF would result into synchronization with the master we are already connected with. No operation performed.");
+            addReplySds(c,sdsnew("+OK Already connected to specified master\r\n"));
+            return;
+        }
+        /* There was no previous master or the user specified a different one,
+         * we can continue. */
         sdsfree(server.masterhost);
         server.masterhost = sdsdup(c->argv[1]->ptr);
-        server.masterport = atoi(c->argv[2]->ptr);
+        server.masterport = port;
         if (server.master) freeClient(server.master);
-        if (server.replstate == REDIS_REPL_TRANSFER)
+        disconnectSlaves(); /* Force our slaves to resync with us as well. */
+        if (server.repl_state == REDIS_REPL_TRANSFER)
             replicationAbortSyncTransfer();
-        server.replstate = REDIS_REPL_CONNECT;
+        server.repl_state = REDIS_REPL_CONNECT;
         redisLog(REDIS_NOTICE,"SLAVE OF %s:%d enabled (user request)",
             server.masterhost, server.masterport);
     }
@@ -535,7 +708,9 @@ void slaveofCommand(redisClient *c) {
 
 void replicationCron(void) {
     /* Non blocking connection timeout? */
-    if (server.masterhost && server.replstate == REDIS_REPL_CONNECTING &&
+    if (server.masterhost &&
+        (server.repl_state == REDIS_REPL_CONNECTING ||
+         server.repl_state == REDIS_REPL_RECEIVE_PONG) &&
         (time(NULL)-server.repl_transfer_lastio) > server.repl_timeout)
     {
         redisLog(REDIS_WARNING,"Timeout connecting to the MASTER...");
@@ -543,7 +718,7 @@ void replicationCron(void) {
     }
 
     /* Bulk transfer I/O timeout? */
-    if (server.masterhost && server.replstate == REDIS_REPL_TRANSFER &&
+    if (server.masterhost && server.repl_state == REDIS_REPL_TRANSFER &&
         (time(NULL)-server.repl_transfer_lastio) > server.repl_timeout)
     {
         redisLog(REDIS_WARNING,"Timeout receiving bulk data from MASTER...");
@@ -551,7 +726,7 @@ void replicationCron(void) {
     }
 
     /* Timed out master when we are an already connected slave? */
-    if (server.masterhost && server.replstate == REDIS_REPL_CONNECTED &&
+    if (server.masterhost && server.repl_state == REDIS_REPL_CONNECTED &&
         (time(NULL)-server.master->lastinteraction) > server.repl_timeout)
     {
         redisLog(REDIS_WARNING,"MASTER time out: no data nor PING received...");
@@ -559,7 +734,7 @@ void replicationCron(void) {
     }
 
     /* Check if we should connect to a MASTER */
-    if (server.replstate == REDIS_REPL_CONNECT) {
+    if (server.repl_state == REDIS_REPL_CONNECT) {
         redisLog(REDIS_NOTICE,"Connecting to MASTER...");
         if (connectWithMaster() == REDIS_OK) {
             redisLog(REDIS_NOTICE,"MASTER <-> SLAVE sync started");
@@ -570,7 +745,7 @@ void replicationCron(void) {
      * So slaves can implement an explicit timeout to masters, and will
      * be able to detect a link disconnection even if the TCP connection
      * will not actually go down. */
-    if (!(server.cronloops % (server.repl_ping_slave_period*10))) {
+    if (!(server.cronloops % (server.repl_ping_slave_period * REDIS_HZ))) {
         listIter li;
         listNode *ln;
 
@@ -583,7 +758,7 @@ void replicationCron(void) {
             if (slave->replstate == REDIS_REPL_SEND_BULK) continue;
             if (slave->replstate == REDIS_REPL_ONLINE) {
                 /* If the slave is online send a normal ping */
-                addReplySds(slave,sdsnew("PING\r\n"));
+                addReplySds(slave,sdsnew("*1\r\n$4\r\nPING\r\n"));
             } else {
                 /* Otherwise we are in the pre-synchronization stage.
                  * Just a newline will do the work of refreshing the