src/replication.c

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