src/replication.c

   1 #include "redis.h"
   2
   3 #include <sys/time.h>
   4 #include <unistd.h>
   5 #include <fcntl.h>
   6 #include <sys/socket.h>
   7 #include <sys/stat.h>
   8
   9 /* ---------------------------------- MASTER -------------------------------- */
  10
  11 void replicationFeedSlaves(list *slaves, int dictid, robj **argv, int argc) {
  12     listNode *ln;
  13     listIter li;
  14     int j;
  15
  16     listRewind(slaves,&li);
  17     while((ln = listNext(&li))) {
  18         redisClient *slave = ln->value;
  19
  20         /* Don't feed slaves that are still waiting for BGSAVE to start */
  21         if (slave->replstate == REDIS_REPL_WAIT_BGSAVE_START) continue;
  22
  23         /* Feed slaves that are waiting for the initial SYNC (so these commands
  24          * are queued in the output buffer until the intial SYNC completes),
  25          * or are already in sync with the master. */
  26         if (slave->slaveseldb != dictid) {
  27             robj *selectcmd;
  28
  29             if (dictid >= 0 && dictid < REDIS_SHARED_SELECT_CMDS) {
  30                 selectcmd = shared.select[dictid];
  31                 incrRefCount(selectcmd);
  32             } else {
  33                 selectcmd = createObject(REDIS_STRING,
  34                     sdscatprintf(sdsempty(),"select %d\r\n",dictid));
  35             }
  36             addReply(slave,selectcmd);
  37             decrRefCount(selectcmd);
  38             slave->slaveseldb = dictid;
  39         }
  40         addReplyMultiBulkLen(slave,argc);
  41         for (j = 0; j < argc; j++) addReplyBulk(slave,argv[j]);
  42     }
  43 }
  44
  45 void replicationFeedMonitors(redisClient *c, list *monitors, int dictid, robj **argv, int argc) {
  46     listNode *ln;
  47     listIter li;
  48     int j, port;
  49     sds cmdrepr = sdsnew("+");
  50     robj *cmdobj;
  51     char ip[32];
  52     struct timeval tv;
  53
  54     gettimeofday(&tv,NULL);
  55     cmdrepr = sdscatprintf(cmdrepr,"%ld.%06ld ",(long)tv.tv_sec,(long)tv.tv_usec);
  56     if (c->flags & REDIS_LUA_CLIENT) {
  57         cmdrepr = sdscatprintf(cmdrepr,"[%d lua] ",dictid);
  58     } else if (c->flags & REDIS_UNIX_SOCKET) {
  59         cmdrepr = sdscatprintf(cmdrepr,"[%d unix:%s] ",dictid,server.unixsocket);
  60     } else {
  61         anetPeerToString(c->fd,ip,&port);
  62         cmdrepr = sdscatprintf(cmdrepr,"[%d %s:%d] ",dictid,ip,port);
  63     }
  64
  65     for (j = 0; j < argc; j++) {
  66         if (argv[j]->encoding == REDIS_ENCODING_INT) {
  67             cmdrepr = sdscatprintf(cmdrepr, "\"%ld\"", (long)argv[j]->ptr);
  68         } else {
  69             cmdrepr = sdscatrepr(cmdrepr,(char*)argv[j]->ptr,
  70                         sdslen(argv[j]->ptr));
  71         }
  72         if (j != argc-1)
  73             cmdrepr = sdscatlen(cmdrepr," ",1);
  74     }
  75     cmdrepr = sdscatlen(cmdrepr,"\r\n",2);
  76     cmdobj = createObject(REDIS_STRING,cmdrepr);
  77
  78     listRewind(monitors,&li);
  79     while((ln = listNext(&li))) {
  80         redisClient *monitor = ln->value;
  81         addReply(monitor,cmdobj);
  82     }
  83     decrRefCount(cmdobj);
  84 }
  85
  86 void syncCommand(redisClient *c) {
  87     /* ignore SYNC if aleady slave or in monitor mode */
  88     if (c->flags & REDIS_SLAVE) return;
  89
  90     /* Refuse SYNC requests if we are a slave but the link with our master
  91      * is not ok... */
  92     if (server.masterhost && server.repl_state != REDIS_REPL_CONNECTED) {
  93         addReplyError(c,"Can't SYNC while not connected with my master");
  94         return;
  95     }
  96
  97     /* SYNC can't be issued when the server has pending data to send to
  98      * the client about already issued commands. We need a fresh reply
  99      * buffer registering the differences between the BGSAVE and the current
 100      * dataset, so that we can copy to other slaves if needed. */
 101     if (listLength(c->reply) != 0) {
 102         addReplyError(c,"SYNC is invalid with pending input");
 103         return;
 104     }
 105
 106     redisLog(REDIS_NOTICE,"Slave ask for synchronization");
 107     /* Here we need to check if there is a background saving operation
 108      * in progress, or if it is required to start one */
 109     if (server.rdb_child_pid != -1) {
 110         /* Ok a background save is in progress. Let's check if it is a good
 111          * one for replication, i.e. if there is another slave that is
 112          * registering differences since the server forked to save */
 113         redisClient *slave;
 114         listNode *ln;
 115         listIter li;
 116
 117         listRewind(server.slaves,&li);
 118         while((ln = listNext(&li))) {
 119             slave = ln->value;
 120             if (slave->replstate == REDIS_REPL_WAIT_BGSAVE_END) break;
 121         }
 122         if (ln) {
 123             /* Perfect, the server is already registering differences for
 124              * another slave. Set the right state, and copy the buffer. */
 125             copyClientOutputBuffer(c,slave);
 126             c->replstate = REDIS_REPL_WAIT_BGSAVE_END;
 127             redisLog(REDIS_NOTICE,"Waiting for end of BGSAVE for SYNC");
 128         } else {
 129             /* No way, we need to wait for the next BGSAVE in order to
 130              * register differences */
 131             c->replstate = REDIS_REPL_WAIT_BGSAVE_START;
 132             redisLog(REDIS_NOTICE,"Waiting for next BGSAVE for SYNC");
 133         }
 134     } else {
 135         /* Ok we don't have a BGSAVE in progress, let's start one */
 136         redisLog(REDIS_NOTICE,"Starting BGSAVE for SYNC");
 137         if (rdbSaveBackground(server.rdb_filename) != REDIS_OK) {
 138             redisLog(REDIS_NOTICE,"Replication failed, can't BGSAVE");
 139             addReplyError(c,"Unable to perform background save");
 140             return;
 141         }
 142         c->replstate = REDIS_REPL_WAIT_BGSAVE_END;
 143     }
 144     c->repldbfd = -1;
 145     c->flags |= REDIS_SLAVE;
 146     c->slaveseldb = 0;
 147     listAddNodeTail(server.slaves,c);
 148     return;
 149 }
 150
 151 /* REPLCONF <option> <value> <option> <value> ...
 152  * This command is used by a slave in order to configure the replication
 153  * process before starting it with the SYNC command.
 154  *
 155  * Currently the only use of this command is to communicate to the master
 156  * what is the listening port of the Slave redis instance, so that the
 157  * master can accurately list slaves and their listening ports in
 158  * the INFO output.
 159  *
 160  * In the future the same command can be used in order to configure
 161  * the replication to initiate an incremental replication instead of a
 162  * full resync. */
 163 void replconfCommand(redisClient *c) {
 164     int j;
 165
 166     if ((c->argc % 2) == 0) {
 167         /* Number of arguments must be odd to make sure that every
 168          * option has a corresponding value. */
 169         addReply(c,shared.syntaxerr);
 170         return;
 171     }
 172
 173     /* Process every option-value pair. */
 174     for (j = 1; j < c->argc; j+=2) {
 175         if (!strcasecmp(c->argv[j]->ptr,"listening-port")) {
 176             long port;
 177
 178             if ((getLongFromObjectOrReply(c,c->argv[j+1],
 179                     &port,NULL) != REDIS_OK))
 180                 return;
 181             c->slave_listening_port = port;
 182         } else {
 183             addReplyErrorFormat(c,"Unrecognized REPLCONF option: %s",
 184                 (char*)c->argv[j]->ptr);
 185             return;
 186         }
 187     }
 188     addReply(c,shared.ok);
 189 }
 190
 191 void sendBulkToSlave(aeEventLoop *el, int fd, void *privdata, int mask) {
 192     redisClient *slave = privdata;
 193     REDIS_NOTUSED(el);
 194     REDIS_NOTUSED(mask);
 195     char buf[REDIS_IOBUF_LEN];
 196     ssize_t nwritten, buflen;
 197
 198     if (slave->repldboff == 0) {
 199         /* Write the bulk write count before to transfer the DB. In theory here
 200          * we don't know how much room there is in the output buffer of the
 201          * socket, but in pratice SO_SNDLOWAT (the minimum count for output
 202          * operations) will never be smaller than the few bytes we need. */
 203         sds bulkcount;
 204
 205         bulkcount = sdscatprintf(sdsempty(),"$%lld\r\n",(unsigned long long)
 206             slave->repldbsize);
 207         if (write(fd,bulkcount,sdslen(bulkcount)) != (signed)sdslen(bulkcount))
 208         {
 209             sdsfree(bulkcount);
 210             freeClient(slave);
 211             return;
 212         }
 213         sdsfree(bulkcount);
 214     }
 215     lseek(slave->repldbfd,slave->repldboff,SEEK_SET);
 216     buflen = read(slave->repldbfd,buf,REDIS_IOBUF_LEN);
 217     if (buflen <= 0) {
 218         redisLog(REDIS_WARNING,"Read error sending DB to slave: %s",
 219             (buflen == 0) ? "premature EOF" : strerror(errno));
 220         freeClient(slave);
 221         return;
 222     }
 223     if ((nwritten = write(fd,buf,buflen)) == -1) {
 224         redisLog(REDIS_VERBOSE,"Write error sending DB to slave: %s",
 225             strerror(errno));
 226         freeClient(slave);
 227         return;
 228     }
 229     slave->repldboff += nwritten;
 230     if (slave->repldboff == slave->repldbsize) {
 231         close(slave->repldbfd);
 232         slave->repldbfd = -1;
 233         aeDeleteFileEvent(server.el,slave->fd,AE_WRITABLE);
 234         slave->replstate = REDIS_REPL_ONLINE;
 235         if (aeCreateFileEvent(server.el, slave->fd, AE_WRITABLE,
 236             sendReplyToClient, slave) == AE_ERR) {
 237             freeClient(slave);
 238             return;
 239         }
 240         redisLog(REDIS_NOTICE,"Synchronization with slave succeeded");
 241     }
 242 }
 243
 244 /* This function is called at the end of every backgrond saving.
 245  * The argument bgsaveerr is REDIS_OK if the background saving succeeded
 246  * otherwise REDIS_ERR is passed to the function.
 247  *
 248  * The goal of this function is to handle slaves waiting for a successful
 249  * background saving in order to perform non-blocking synchronization. */
 250 void updateSlavesWaitingBgsave(int bgsaveerr) {
 251     listNode *ln;
 252     int startbgsave = 0;
 253     listIter li;
 254
 255     listRewind(server.slaves,&li);
 256     while((ln = listNext(&li))) {
 257         redisClient *slave = ln->value;
 258
 259         if (slave->replstate == REDIS_REPL_WAIT_BGSAVE_START) {
 260             startbgsave = 1;
 261             slave->replstate = REDIS_REPL_WAIT_BGSAVE_END;
 262         } else if (slave->replstate == REDIS_REPL_WAIT_BGSAVE_END) {
 263             struct redis_stat buf;
 264
 265             if (bgsaveerr != REDIS_OK) {
 266                 freeClient(slave);
 267                 redisLog(REDIS_WARNING,"SYNC failed. BGSAVE child returned an error");
 268                 continue;
 269             }
 270             if ((slave->repldbfd = open(server.rdb_filename,O_RDONLY)) == -1 ||
 271                 redis_fstat(slave->repldbfd,&buf) == -1) {
 272                 freeClient(slave);
 273                 redisLog(REDIS_WARNING,"SYNC failed. Can't open/stat DB after BGSAVE: %s", strerror(errno));
 274                 continue;
 275             }
 276             slave->repldboff = 0;
 277             slave->repldbsize = buf.st_size;
 278             slave->replstate = REDIS_REPL_SEND_BULK;
 279             aeDeleteFileEvent(server.el,slave->fd,AE_WRITABLE);
 280             if (aeCreateFileEvent(server.el, slave->fd, AE_WRITABLE, sendBulkToSlave, slave) == AE_ERR) {
 281                 freeClient(slave);
 282                 continue;
 283             }
 284         }
 285     }
 286     if (startbgsave) {
 287         if (rdbSaveBackground(server.rdb_filename) != REDIS_OK) {
 288             listIter li;
 289
 290             listRewind(server.slaves,&li);
 291             redisLog(REDIS_WARNING,"SYNC failed. BGSAVE failed");
 292             while((ln = listNext(&li))) {
 293                 redisClient *slave = ln->value;
 294
 295                 if (slave->replstate == REDIS_REPL_WAIT_BGSAVE_START)
 296                     freeClient(slave);
 297             }
 298         }
 299     }
 300 }
 301
 302 /* ----------------------------------- SLAVE -------------------------------- */
 303
 304 /* Abort the async download of the bulk dataset while SYNC-ing with master */
 305 void replicationAbortSyncTransfer(void) {
 306     redisAssert(server.repl_state == REDIS_REPL_TRANSFER);
 307
 308     aeDeleteFileEvent(server.el,server.repl_transfer_s,AE_READABLE);
 309     close(server.repl_transfer_s);
 310     close(server.repl_transfer_fd);
 311     unlink(server.repl_transfer_tmpfile);
 312     zfree(server.repl_transfer_tmpfile);
 313     server.repl_state = REDIS_REPL_CONNECT;
 314 }
 315
 316 /* Asynchronously read the SYNC payload we receive from a master */
 317 #define REPL_MAX_WRITTEN_BEFORE_FSYNC (1024*1024*8) /* 8 MB */
 318 void readSyncBulkPayload(aeEventLoop *el, int fd, void *privdata, int mask) {
 319     char buf[4096];
 320     ssize_t nread, readlen;
 321     off_t left;
 322     REDIS_NOTUSED(el);
 323     REDIS_NOTUSED(privdata);
 324     REDIS_NOTUSED(mask);
 325
 326     /* If repl_transfer_size == -1 we still have to read the bulk length
 327      * from the master reply. */
 328     if (server.repl_transfer_size == -1) {
 329         if (syncReadLine(fd,buf,1024,server.repl_syncio_timeout*1000) == -1) {
 330             redisLog(REDIS_WARNING,
 331                 "I/O error reading bulk count from MASTER: %s",
 332                 strerror(errno));
 333             goto error;
 334         }
 335
 336         if (buf[0] == '-') {
 337             redisLog(REDIS_WARNING,
 338                 "MASTER aborted replication with an error: %s",
 339                 buf+1);
 340             goto error;
 341         } else if (buf[0] == '\0') {
 342             /* At this stage just a newline works as a PING in order to take
 343              * the connection live. So we refresh our last interaction
 344              * timestamp. */
 345             server.repl_transfer_lastio = server.unixtime;
 346             return;
 347         } else if (buf[0] != '$') {
 348             redisLog(REDIS_WARNING,"Bad protocol from MASTER, the first byte is not '$', are you sure the host and port are right?");
 349             goto error;
 350         }
 351         server.repl_transfer_size = strtol(buf+1,NULL,10);
 352         redisLog(REDIS_NOTICE,
 353             "MASTER <-> SLAVE sync: receiving %ld bytes from master",
 354             server.repl_transfer_size);
 355         return;
 356     }
 357
 358     /* Read bulk data */
 359     left = server.repl_transfer_size - server.repl_transfer_read;
 360     readlen = (left < (signed)sizeof(buf)) ? left : (signed)sizeof(buf);
 361     nread = read(fd,buf,readlen);
 362     if (nread <= 0) {
 363         redisLog(REDIS_WARNING,"I/O error trying to sync with MASTER: %s",
 364             (nread == -1) ? strerror(errno) : "connection lost");
 365         replicationAbortSyncTransfer();
 366         return;
 367     }
 368     server.repl_transfer_lastio = server.unixtime;
 369     if (write(server.repl_transfer_fd,buf,nread) != nread) {
 370         redisLog(REDIS_WARNING,"Write error or short write writing to the DB dump file needed for MASTER <-> SLAVE synchronization: %s", strerror(errno));
 371         goto error;
 372     }
 373     server.repl_transfer_read += nread;
 374
 375     /* Sync data on disk from time to time, otherwise at the end of the transfer
 376      * we may suffer a big delay as the memory buffers are copied into the
 377      * actual disk. */
 378     if (server.repl_transfer_read >=
 379         server.repl_transfer_last_fsync_off + REPL_MAX_WRITTEN_BEFORE_FSYNC)
 380     {
 381         off_t sync_size = server.repl_transfer_read -
 382                           server.repl_transfer_last_fsync_off;
 383         rdb_fsync_range(server.repl_transfer_fd,
 384             server.repl_transfer_last_fsync_off, sync_size);
 385         server.repl_transfer_last_fsync_off += sync_size;
 386     }
 387
 388     /* Check if the transfer is now complete */
 389     if (server.repl_transfer_read == server.repl_transfer_size) {
 390         if (rename(server.repl_transfer_tmpfile,server.rdb_filename) == -1) {
 391             redisLog(REDIS_WARNING,"Failed trying to rename the temp DB into dump.rdb in MASTER <-> SLAVE synchronization: %s", strerror(errno));
 392             replicationAbortSyncTransfer();
 393             return;
 394         }
 395         redisLog(REDIS_NOTICE, "MASTER <-> SLAVE sync: Loading DB in memory");
 396         emptyDb();
 397         /* Before loading the DB into memory we need to delete the readable
 398          * handler, otherwise it will get called recursively since
 399          * rdbLoad() will call the event loop to process events from time to
 400          * time for non blocking loading. */
 401         aeDeleteFileEvent(server.el,server.repl_transfer_s,AE_READABLE);
 402         if (rdbLoad(server.rdb_filename) != REDIS_OK) {
 403             redisLog(REDIS_WARNING,"Failed trying to load the MASTER synchronization DB from disk");
 404             replicationAbortSyncTransfer();
 405             return;
 406         }
 407         /* Final setup of the connected slave <- master link */
 408         zfree(server.repl_transfer_tmpfile);
 409         close(server.repl_transfer_fd);
 410         server.master = createClient(server.repl_transfer_s);
 411         server.master->flags |= REDIS_MASTER;
 412         server.master->authenticated = 1;
 413         server.repl_state = REDIS_REPL_CONNECTED;
 414         redisLog(REDIS_NOTICE, "MASTER <-> SLAVE sync: Finished with success");
 415         /* Restart the AOF subsystem now that we finished the sync. This
 416          * will trigger an AOF rewrite, and when done will start appending
 417          * to the new file. */
 418         if (server.aof_state != REDIS_AOF_OFF) {
 419             int retry = 10;
 420
 421             stopAppendOnly();
 422             while (retry-- && startAppendOnly() == REDIS_ERR) {
 423                 redisLog(REDIS_WARNING,"Failed enabling the AOF after successful master synchrnization! Trying it again in one second.");
 424                 sleep(1);
 425             }
 426             if (!retry) {
 427                 redisLog(REDIS_WARNING,"FATAL: this slave instance finished the synchronization with its master, but the AOF can't be turned on. Exiting now.");
 428                 exit(1);
 429             }
 430         }
 431     }
 432
 433     return;
 434
 435 error:
 436     replicationAbortSyncTransfer();
 437     return;
 438 }
 439
 440 /* Send a synchronous command to the master. Used to send AUTH and
 441  * REPLCONF commands before starting the replication with SYNC.
 442  *
 443  * On success NULL is returned.
 444  * On error an sds string describing the error is returned.
 445  */
 446 char *sendSynchronousCommand(int fd, ...) {
 447     va_list ap;
 448     sds cmd = sdsempty();
 449     char *arg, buf[256];
 450
 451     /* Create the command to send to the master, we use simple inline
 452      * protocol for simplicity as currently we only send simple strings. */
 453     va_start(ap,fd);
 454     while(1) {
 455         arg = va_arg(ap, char*);
 456         if (arg == NULL) break;
 457
 458         if (sdslen(cmd) != 0) cmd = sdscatlen(cmd," ",1);
 459         cmd = sdscat(cmd,arg);
 460     }
 461     cmd = sdscatlen(cmd,"\r\n",2);
 462
 463     /* Transfer command to the server. */
 464     if (syncWrite(fd,cmd,sdslen(cmd),server.repl_syncio_timeout*1000) == -1) {
 465         sdsfree(cmd);
 466         return sdscatprintf(sdsempty(),"Writing to master: %s",
 467                 strerror(errno));
 468     }
 469     sdsfree(cmd);
 470
 471     /* Read the reply from the server. */
 472     if (syncReadLine(fd,buf,sizeof(buf),server.repl_syncio_timeout*1000) == -1)
 473     {
 474         return sdscatprintf(sdsempty(),"Reading from master: %s",
 475                 strerror(errno));
 476     }
 477
 478     /* Check for errors from the server. */
 479     if (buf[0] != '+') {
 480         return sdscatprintf(sdsempty(),"Error from master: %s", buf);
 481     }
 482
 483     return NULL; /* No errors. */
 484 }
 485
 486 void syncWithMaster(aeEventLoop *el, int fd, void *privdata, int mask) {
 487     char tmpfile[256], *err;
 488     int dfd, maxtries = 5;
 489     int sockerr = 0;
 490     socklen_t errlen = sizeof(sockerr);
 491     REDIS_NOTUSED(el);
 492     REDIS_NOTUSED(privdata);
 493     REDIS_NOTUSED(mask);
 494
 495     /* If this event fired after the user turned the instance into a master
 496      * with SLAVEOF NO ONE we must just return ASAP. */
 497     if (server.repl_state == REDIS_REPL_NONE) {
 498         close(fd);
 499         return;
 500     }
 501
 502     /* Check for errors in the socket. */
 503     if (getsockopt(fd, SOL_SOCKET, SO_ERROR, &sockerr, &errlen) == -1)
 504         sockerr = errno;
 505     if (sockerr) {
 506         aeDeleteFileEvent(server.el,fd,AE_READABLE|AE_WRITABLE);
 507         redisLog(REDIS_WARNING,"Error condition on socket for SYNC: %s",
 508             strerror(sockerr));
 509         goto error;
 510     }
 511
 512     /* If we were connecting, it's time to send a non blocking PING, we want to
 513      * make sure the master is able to reply before going into the actual
 514      * replication process where we have long timeouts in the order of
 515      * seconds (in the meantime the slave would block). */
 516     if (server.repl_state == REDIS_REPL_CONNECTING) {
 517         redisLog(REDIS_NOTICE,"Non blocking connect for SYNC fired the event.");
 518         /* Delete the writable event so that the readable event remains
 519          * registered and we can wait for the PONG reply. */
 520         aeDeleteFileEvent(server.el,fd,AE_WRITABLE);
 521         server.repl_state = REDIS_REPL_RECEIVE_PONG;
 522         /* Send the PING, don't check for errors at all, we have the timeout
 523          * that will take care about this. */
 524         syncWrite(fd,"PING\r\n",6,100);
 525         return;
 526     }
 527
 528     /* Receive the PONG command. */
 529     if (server.repl_state == REDIS_REPL_RECEIVE_PONG) {
 530         char buf[1024];
 531
 532         /* Delete the readable event, we no longer need it now that there is
 533          * the PING reply to read. */
 534         aeDeleteFileEvent(server.el,fd,AE_READABLE);
 535
 536         /* Read the reply with explicit timeout. */
 537         buf[0] = '\0';
 538         if (syncReadLine(fd,buf,sizeof(buf),
 539             server.repl_syncio_timeout*1000) == -1)
 540         {
 541             redisLog(REDIS_WARNING,
 542                 "I/O error reading PING reply from master: %s",
 543                 strerror(errno));
 544             goto error;
 545         }
 546
 547         /* We don't care about the reply, it can be +PONG or an error since
 548          * the server requires AUTH. As long as it replies correctly, it's
 549          * fine from our point of view. */
 550         if (buf[0] != '-' && buf[0] != '+') {
 551             redisLog(REDIS_WARNING,"Unexpected reply to PING from master.");
 552             goto error;
 553         } else {
 554             redisLog(REDIS_NOTICE,
 555                 "Master replied to PING, replication can continue...");
 556         }
 557     }
 558
 559     /* AUTH with the master if required. */
 560     if(server.masterauth) {
 561         err = sendSynchronousCommand(fd,"AUTH",server.masterauth,NULL);
 562         if (err) {
 563             redisLog(REDIS_WARNING,"Unable to AUTH to MASTER: %s",err);
 564             sdsfree(err);
 565             goto error;
 566         }
 567     }
 568
 569     /* Set the slave port, so that Master's INFO command can list the
 570      * slave listening port correctly. */
 571     {
 572         sds port = sdsfromlonglong(server.port);
 573         err = sendSynchronousCommand(fd,"REPLCONF","listening-port",port,
 574                                          NULL);
 575         sdsfree(port);
 576         /* Ignore the error if any, not all the Redis versions support
 577          * REPLCONF listening-port. */
 578         if (err) {
 579             redisLog(REDIS_NOTICE,"(non critical): Master does not understand REPLCONF listening-port: %s", err);
 580             sdsfree(err);
 581         }
 582     }
 583
 584     /* Issue the SYNC command */
 585     if (syncWrite(fd,"SYNC\r\n",6,server.repl_syncio_timeout*1000) == -1) {
 586         redisLog(REDIS_WARNING,"I/O error writing to MASTER: %s",
 587             strerror(errno));
 588         goto error;
 589     }
 590
 591     /* Prepare a suitable temp file for bulk transfer */
 592     while(maxtries--) {
 593         snprintf(tmpfile,256,
 594             "temp-%d.%ld.rdb",(int)server.unixtime,(long int)getpid());
 595         dfd = open(tmpfile,O_CREAT|O_WRONLY|O_EXCL,0644);
 596         if (dfd != -1) break;
 597         sleep(1);
 598     }
 599     if (dfd == -1) {
 600         redisLog(REDIS_WARNING,"Opening the temp file needed for MASTER <-> SLAVE synchronization: %s",strerror(errno));
 601         goto error;
 602     }
 603
 604     /* Setup the non blocking download of the bulk file. */
 605     if (aeCreateFileEvent(server.el,fd, AE_READABLE,readSyncBulkPayload,NULL)
 606             == AE_ERR)
 607     {
 608         redisLog(REDIS_WARNING,"Can't create readable event for SYNC");
 609         goto error;
 610     }
 611
 612     server.repl_state = REDIS_REPL_TRANSFER;
 613     server.repl_transfer_size = -1;
 614     server.repl_transfer_read = 0;
 615     server.repl_transfer_last_fsync_off = 0;
 616     server.repl_transfer_fd = dfd;
 617     server.repl_transfer_lastio = server.unixtime;
 618     server.repl_transfer_tmpfile = zstrdup(tmpfile);
 619     return;
 620
 621 error:
 622     close(fd);
 623     server.repl_transfer_s = -1;
 624     server.repl_state = REDIS_REPL_CONNECT;
 625     return;
 626 }
 627
 628 int connectWithMaster(void) {
 629     int fd;
 630
 631     fd = anetTcpNonBlockConnect(NULL,server.masterhost,server.masterport);
 632     if (fd == -1) {
 633         redisLog(REDIS_WARNING,"Unable to connect to MASTER: %s",
 634             strerror(errno));
 635         return REDIS_ERR;
 636     }
 637
 638     if (aeCreateFileEvent(server.el,fd,AE_READABLE|AE_WRITABLE,syncWithMaster,NULL) ==
 639             AE_ERR)
 640     {
 641         close(fd);
 642         redisLog(REDIS_WARNING,"Can't create readable event for SYNC");
 643         return REDIS_ERR;
 644     }
 645
 646     server.repl_transfer_lastio = server.unixtime;
 647     server.repl_transfer_s = fd;
 648     server.repl_state = REDIS_REPL_CONNECTING;
 649     return REDIS_OK;
 650 }
 651
 652 /* This function can be called when a non blocking connection is currently
 653  * in progress to undo it. */
 654 void undoConnectWithMaster(void) {
 655     int fd = server.repl_transfer_s;
 656
 657     redisAssert(server.repl_state == REDIS_REPL_CONNECTING ||
 658                 server.repl_state == REDIS_REPL_RECEIVE_PONG);
 659     aeDeleteFileEvent(server.el,fd,AE_READABLE|AE_WRITABLE);
 660     close(fd);
 661     server.repl_transfer_s = -1;
 662     server.repl_state = REDIS_REPL_CONNECT;
 663 }
 664
 665 void slaveofCommand(redisClient *c) {
 666     if (!strcasecmp(c->argv[1]->ptr,"no") &&
 667         !strcasecmp(c->argv[2]->ptr,"one")) {
 668         if (server.masterhost) {
 669             sdsfree(server.masterhost);
 670             server.masterhost = NULL;
 671             if (server.master) freeClient(server.master);
 672             if (server.repl_state == REDIS_REPL_TRANSFER)
 673                 replicationAbortSyncTransfer();
 674             else if (server.repl_state == REDIS_REPL_CONNECTING ||
 675                      server.repl_state == REDIS_REPL_RECEIVE_PONG)
 676                 undoConnectWithMaster();
 677             server.repl_state = REDIS_REPL_NONE;
 678             redisLog(REDIS_NOTICE,"MASTER MODE enabled (user request)");
 679         }
 680     } else {
 681         long port;
 682
 683         if ((getLongFromObjectOrReply(c, c->argv[2], &port, NULL) != REDIS_OK))
 684             return;
 685
 686         /* Check if we are already attached to the specified slave */
 687         if (server.masterhost && !strcasecmp(server.masterhost,c->argv[1]->ptr)
 688             && server.masterport == port) {
 689             redisLog(REDIS_NOTICE,"SLAVE OF would result into synchronization with the master we are already connected with. No operation performed.");
 690             addReplySds(c,sdsnew("+OK Already connected to specified master\r\n"));
 691             return;
 692         }
 693         /* There was no previous master or the user specified a different one,
 694          * we can continue. */
 695         sdsfree(server.masterhost);
 696         server.masterhost = sdsdup(c->argv[1]->ptr);
 697         server.masterport = port;
 698         if (server.master) freeClient(server.master);
 699         disconnectSlaves(); /* Force our slaves to resync with us as well. */
 700         if (server.repl_state == REDIS_REPL_TRANSFER)
 701             replicationAbortSyncTransfer();
 702         server.repl_state = REDIS_REPL_CONNECT;
 703         redisLog(REDIS_NOTICE,"SLAVE OF %s:%d enabled (user request)",
 704             server.masterhost, server.masterport);
 705     }
 706     addReply(c,shared.ok);
 707 }
 708
 709 /* --------------------------- REPLICATION CRON  ---------------------------- */
 710
 711 void replicationCron(void) {
 712     /* Non blocking connection timeout? */
 713     if (server.masterhost &&
 714         (server.repl_state == REDIS_REPL_CONNECTING ||
 715          server.repl_state == REDIS_REPL_RECEIVE_PONG) &&
 716         (time(NULL)-server.repl_transfer_lastio) > server.repl_timeout)
 717     {
 718         redisLog(REDIS_WARNING,"Timeout connecting to the MASTER...");
 719         undoConnectWithMaster();
 720     }
 721
 722     /* Bulk transfer I/O timeout? */
 723     if (server.masterhost && server.repl_state == REDIS_REPL_TRANSFER &&
 724         (time(NULL)-server.repl_transfer_lastio) > server.repl_timeout)
 725     {
 726         redisLog(REDIS_WARNING,"Timeout receiving bulk data from MASTER... If the problem persists try to set the 'repl-timeout' parameter in redis.conf to a larger value.");
 727         replicationAbortSyncTransfer();
 728     }
 729
 730     /* Timed out master when we are an already connected slave? */
 731     if (server.masterhost && server.repl_state == REDIS_REPL_CONNECTED &&
 732         (time(NULL)-server.master->lastinteraction) > server.repl_timeout)
 733     {
 734         redisLog(REDIS_WARNING,"MASTER time out: no data nor PING received...");
 735         freeClient(server.master);
 736     }
 737
 738     /* Check if we should connect to a MASTER */
 739     if (server.repl_state == REDIS_REPL_CONNECT) {
 740         redisLog(REDIS_NOTICE,"Connecting to MASTER...");
 741         if (connectWithMaster() == REDIS_OK) {
 742             redisLog(REDIS_NOTICE,"MASTER <-> SLAVE sync started");
 743         }
 744     }
 745
 746     /* If we have attached slaves, PING them from time to time.
 747      * So slaves can implement an explicit timeout to masters, and will
 748      * be able to detect a link disconnection even if the TCP connection
 749      * will not actually go down. */
 750     if (!(server.cronloops % (server.repl_ping_slave_period * REDIS_HZ))) {
 751         listIter li;
 752         listNode *ln;
 753
 754         listRewind(server.slaves,&li);
 755         while((ln = listNext(&li))) {
 756             redisClient *slave = ln->value;
 757
 758             /* Don't ping slaves that are in the middle of a bulk transfer
 759              * with the master for first synchronization. */
 760             if (slave->replstate == REDIS_REPL_SEND_BULK) continue;
 761             if (slave->replstate == REDIS_REPL_ONLINE) {
 762                 /* If the slave is online send a normal ping */
 763                 addReplySds(slave,sdsnew("*1\r\n$4\r\nPING\r\n"));
 764             } else {
 765                 /* Otherwise we are in the pre-synchronization stage.
 766                  * Just a newline will do the work of refreshing the
 767                  * connection last interaction time, and at the same time
 768                  * we'll be sure that being a single char there are no
 769                  * short-write problems. */
 770                 if (write(slave->fd, "\n", 1) == -1) {
 771                     /* Don't worry, it's just a ping. */
 772                 }
 773             }
 774         }
 775     }
 776 }