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