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 void sendBulkToSlave(aeEventLoop *el, int fd, void *privdata, int mask) {
 149     redisClient *slave = privdata;
 150     REDIS_NOTUSED(el);
 151     REDIS_NOTUSED(mask);
 152     char buf[REDIS_IOBUF_LEN];
 153     ssize_t nwritten, buflen;
 154
 155     if (slave->repldboff == 0) {
 156         /* Write the bulk write count before to transfer the DB. In theory here
 157          * we don't know how much room there is in the output buffer of the
 158          * socket, but in pratice SO_SNDLOWAT (the minimum count for output
 159          * operations) will never be smaller than the few bytes we need. */
 160         sds bulkcount;
 161
 162         bulkcount = sdscatprintf(sdsempty(),"$%lld\r\n",(unsigned long long)
 163             slave->repldbsize);
 164         if (write(fd,bulkcount,sdslen(bulkcount)) != (signed)sdslen(bulkcount))
 165         {
 166             sdsfree(bulkcount);
 167             freeClient(slave);
 168             return;
 169         }
 170         sdsfree(bulkcount);
 171     }
 172     lseek(slave->repldbfd,slave->repldboff,SEEK_SET);
 173     buflen = read(slave->repldbfd,buf,REDIS_IOBUF_LEN);
 174     if (buflen <= 0) {
 175         redisLog(REDIS_WARNING,"Read error sending DB to slave: %s",
 176             (buflen == 0) ? "premature EOF" : strerror(errno));
 177         freeClient(slave);
 178         return;
 179     }
 180     if ((nwritten = write(fd,buf,buflen)) == -1) {
 181         redisLog(REDIS_VERBOSE,"Write error sending DB to slave: %s",
 182             strerror(errno));
 183         freeClient(slave);
 184         return;
 185     }
 186     slave->repldboff += nwritten;
 187     if (slave->repldboff == slave->repldbsize) {
 188         close(slave->repldbfd);
 189         slave->repldbfd = -1;
 190         aeDeleteFileEvent(server.el,slave->fd,AE_WRITABLE);
 191         slave->replstate = REDIS_REPL_ONLINE;
 192         if (aeCreateFileEvent(server.el, slave->fd, AE_WRITABLE,
 193             sendReplyToClient, slave) == AE_ERR) {
 194             freeClient(slave);
 195             return;
 196         }
 197         redisLog(REDIS_NOTICE,"Synchronization with slave succeeded");
 198     }
 199 }
 200
 201 /* This function is called at the end of every backgrond saving.
 202  * The argument bgsaveerr is REDIS_OK if the background saving succeeded
 203  * otherwise REDIS_ERR is passed to the function.
 204  *
 205  * The goal of this function is to handle slaves waiting for a successful
 206  * background saving in order to perform non-blocking synchronization. */
 207 void updateSlavesWaitingBgsave(int bgsaveerr) {
 208     listNode *ln;
 209     int startbgsave = 0;
 210     listIter li;
 211
 212     listRewind(server.slaves,&li);
 213     while((ln = listNext(&li))) {
 214         redisClient *slave = ln->value;
 215
 216         if (slave->replstate == REDIS_REPL_WAIT_BGSAVE_START) {
 217             startbgsave = 1;
 218             slave->replstate = REDIS_REPL_WAIT_BGSAVE_END;
 219         } else if (slave->replstate == REDIS_REPL_WAIT_BGSAVE_END) {
 220             struct redis_stat buf;
 221
 222             if (bgsaveerr != REDIS_OK) {
 223                 freeClient(slave);
 224                 redisLog(REDIS_WARNING,"SYNC failed. BGSAVE child returned an error");
 225                 continue;
 226             }
 227             if ((slave->repldbfd = open(server.rdb_filename,O_RDONLY)) == -1 ||
 228                 redis_fstat(slave->repldbfd,&buf) == -1) {
 229                 freeClient(slave);
 230                 redisLog(REDIS_WARNING,"SYNC failed. Can't open/stat DB after BGSAVE: %s", strerror(errno));
 231                 continue;
 232             }
 233             slave->repldboff = 0;
 234             slave->repldbsize = buf.st_size;
 235             slave->replstate = REDIS_REPL_SEND_BULK;
 236             aeDeleteFileEvent(server.el,slave->fd,AE_WRITABLE);
 237             if (aeCreateFileEvent(server.el, slave->fd, AE_WRITABLE, sendBulkToSlave, slave) == AE_ERR) {
 238                 freeClient(slave);
 239                 continue;
 240             }
 241         }
 242     }
 243     if (startbgsave) {
 244         if (rdbSaveBackground(server.rdb_filename) != REDIS_OK) {
 245             listIter li;
 246
 247             listRewind(server.slaves,&li);
 248             redisLog(REDIS_WARNING,"SYNC failed. BGSAVE failed");
 249             while((ln = listNext(&li))) {
 250                 redisClient *slave = ln->value;
 251
 252                 if (slave->replstate == REDIS_REPL_WAIT_BGSAVE_START)
 253                     freeClient(slave);
 254             }
 255         }
 256     }
 257 }
 258
 259 /* ----------------------------------- SLAVE -------------------------------- */
 260
 261 /* Abort the async download of the bulk dataset while SYNC-ing with master */
 262 void replicationAbortSyncTransfer(void) {
 263     redisAssert(server.repl_state == REDIS_REPL_TRANSFER);
 264
 265     aeDeleteFileEvent(server.el,server.repl_transfer_s,AE_READABLE);
 266     close(server.repl_transfer_s);
 267     close(server.repl_transfer_fd);
 268     unlink(server.repl_transfer_tmpfile);
 269     zfree(server.repl_transfer_tmpfile);
 270     server.repl_state = REDIS_REPL_CONNECT;
 271 }
 272
 273 /* Asynchronously read the SYNC payload we receive from a master */
 274 void readSyncBulkPayload(aeEventLoop *el, int fd, void *privdata, int mask) {
 275     char buf[4096];
 276     ssize_t nread, readlen;
 277     REDIS_NOTUSED(el);
 278     REDIS_NOTUSED(privdata);
 279     REDIS_NOTUSED(mask);
 280
 281     /* If repl_transfer_left == -1 we still have to read the bulk length
 282      * from the master reply. */
 283     if (server.repl_transfer_left == -1) {
 284         if (syncReadLine(fd,buf,1024,server.repl_syncio_timeout*1000) == -1) {
 285             redisLog(REDIS_WARNING,
 286                 "I/O error reading bulk count from MASTER: %s",
 287                 strerror(errno));
 288             goto error;
 289         }
 290
 291         if (buf[0] == '-') {
 292             redisLog(REDIS_WARNING,
 293                 "MASTER aborted replication with an error: %s",
 294                 buf+1);
 295             goto error;
 296         } else if (buf[0] == '\0') {
 297             /* At this stage just a newline works as a PING in order to take
 298              * the connection live. So we refresh our last interaction
 299              * timestamp. */
 300             server.repl_transfer_lastio = server.unixtime;
 301             return;
 302         } else if (buf[0] != '$') {
 303             redisLog(REDIS_WARNING,"Bad protocol from MASTER, the first byte is not '$', are you sure the host and port are right?");
 304             goto error;
 305         }
 306         server.repl_transfer_left = strtol(buf+1,NULL,10);
 307         redisLog(REDIS_NOTICE,
 308             "MASTER <-> SLAVE sync: receiving %ld bytes from master",
 309             server.repl_transfer_left);
 310         return;
 311     }
 312
 313     /* Read bulk data */
 314     readlen = (server.repl_transfer_left < (signed)sizeof(buf)) ?
 315         server.repl_transfer_left : (signed)sizeof(buf);
 316     nread = read(fd,buf,readlen);
 317     if (nread <= 0) {
 318         redisLog(REDIS_WARNING,"I/O error trying to sync with MASTER: %s",
 319             (nread == -1) ? strerror(errno) : "connection lost");
 320         replicationAbortSyncTransfer();
 321         return;
 322     }
 323     server.repl_transfer_lastio = server.unixtime;
 324     if (write(server.repl_transfer_fd,buf,nread) != nread) {
 325         redisLog(REDIS_WARNING,"Write error or short write writing to the DB dump file needed for MASTER <-> SLAVE synchronization: %s", strerror(errno));
 326         goto error;
 327     }
 328     server.repl_transfer_left -= nread;
 329     /* Check if the transfer is now complete */
 330     if (server.repl_transfer_left == 0) {
 331         if (rename(server.repl_transfer_tmpfile,server.rdb_filename) == -1) {
 332             redisLog(REDIS_WARNING,"Failed trying to rename the temp DB into dump.rdb in MASTER <-> SLAVE synchronization: %s", strerror(errno));
 333             replicationAbortSyncTransfer();
 334             return;
 335         }
 336         redisLog(REDIS_NOTICE, "MASTER <-> SLAVE sync: Loading DB in memory");
 337         emptyDb();
 338         /* Before loading the DB into memory we need to delete the readable
 339          * handler, otherwise it will get called recursively since
 340          * rdbLoad() will call the event loop to process events from time to
 341          * time for non blocking loading. */
 342         aeDeleteFileEvent(server.el,server.repl_transfer_s,AE_READABLE);
 343         if (rdbLoad(server.rdb_filename) != REDIS_OK) {
 344             redisLog(REDIS_WARNING,"Failed trying to load the MASTER synchronization DB from disk");
 345             replicationAbortSyncTransfer();
 346             return;
 347         }
 348         /* Final setup of the connected slave <- master link */
 349         zfree(server.repl_transfer_tmpfile);
 350         close(server.repl_transfer_fd);
 351         server.master = createClient(server.repl_transfer_s);
 352         server.master->flags |= REDIS_MASTER;
 353         server.master->authenticated = 1;
 354         server.repl_state = REDIS_REPL_CONNECTED;
 355         redisLog(REDIS_NOTICE, "MASTER <-> SLAVE sync: Finished with success");
 356         /* Restart the AOF subsystem now that we finished the sync. This
 357          * will trigger an AOF rewrite, and when done will start appending
 358          * to the new file. */
 359         if (server.aof_state != REDIS_AOF_OFF) {
 360             int retry = 10;
 361
 362             stopAppendOnly();
 363             while (retry-- && startAppendOnly() == REDIS_ERR) {
 364                 redisLog(REDIS_WARNING,"Failed enabling the AOF after successful master synchrnization! Trying it again in one second.");
 365                 sleep(1);
 366             }
 367             if (!retry) {
 368                 redisLog(REDIS_WARNING,"FATAL: this slave instance finished the synchronization with its master, but the AOF can't be turned on. Exiting now.");
 369                 exit(1);
 370             }
 371         }
 372     }
 373
 374     return;
 375
 376 error:
 377     replicationAbortSyncTransfer();
 378     return;
 379 }
 380
 381 void syncWithMaster(aeEventLoop *el, int fd, void *privdata, int mask) {
 382     char buf[1024], tmpfile[256];
 383     int dfd, maxtries = 5;
 384     REDIS_NOTUSED(el);
 385     REDIS_NOTUSED(privdata);
 386     REDIS_NOTUSED(mask);
 387
 388     /* If this event fired after the user turned the instance into a master
 389      * with SLAVEOF NO ONE we must just return ASAP. */
 390     if (server.repl_state == REDIS_REPL_NONE) {
 391         close(fd);
 392         return;
 393     }
 394
 395     redisLog(REDIS_NOTICE,"Non blocking connect for SYNC fired the event.");
 396     /* This event should only be triggered once since it is used to have a
 397      * non-blocking connect(2) to the master. It has been triggered when this
 398      * function is called, so we can delete it. */
 399     aeDeleteFileEvent(server.el,fd,AE_READABLE|AE_WRITABLE);
 400
 401     /* AUTH with the master if required. */
 402     if(server.masterauth) {
 403         char authcmd[1024];
 404         size_t authlen;
 405
 406         authlen = snprintf(authcmd,sizeof(authcmd),"AUTH %s\r\n",server.masterauth);
 407         if (syncWrite(fd,authcmd,authlen,server.repl_syncio_timeout*1000) == -1) {
 408             redisLog(REDIS_WARNING,"Unable to AUTH to MASTER: %s",
 409                 strerror(errno));
 410             goto error;
 411         }
 412         /* Read the AUTH result.  */
 413         if (syncReadLine(fd,buf,1024,server.repl_syncio_timeout*1000) == -1) {
 414             redisLog(REDIS_WARNING,"I/O error reading auth result from MASTER: %s",
 415                 strerror(errno));
 416             goto error;
 417         }
 418         if (buf[0] != '+') {
 419             redisLog(REDIS_WARNING,"Cannot AUTH to MASTER, is the masterauth password correct?");
 420             goto error;
 421         }
 422     }
 423
 424     /* Issue the SYNC command */
 425     if (syncWrite(fd,"SYNC\r\n",6,server.repl_syncio_timeout*1000) == -1) {
 426         redisLog(REDIS_WARNING,"I/O error writing to MASTER: %s",
 427             strerror(errno));
 428         goto error;
 429     }
 430
 431     /* Prepare a suitable temp file for bulk transfer */
 432     while(maxtries--) {
 433         snprintf(tmpfile,256,
 434             "temp-%d.%ld.rdb",(int)server.unixtime,(long int)getpid());
 435         dfd = open(tmpfile,O_CREAT|O_WRONLY|O_EXCL,0644);
 436         if (dfd != -1) break;
 437         sleep(1);
 438     }
 439     if (dfd == -1) {
 440         redisLog(REDIS_WARNING,"Opening the temp file needed for MASTER <-> SLAVE synchronization: %s",strerror(errno));
 441         goto error;
 442     }
 443
 444     /* Setup the non blocking download of the bulk file. */
 445     if (aeCreateFileEvent(server.el,fd, AE_READABLE,readSyncBulkPayload,NULL)
 446             == AE_ERR)
 447     {
 448         redisLog(REDIS_WARNING,"Can't create readable event for SYNC");
 449         goto error;
 450     }
 451
 452     server.repl_state = REDIS_REPL_TRANSFER;
 453     server.repl_transfer_left = -1;
 454     server.repl_transfer_fd = dfd;
 455     server.repl_transfer_lastio = server.unixtime;
 456     server.repl_transfer_tmpfile = zstrdup(tmpfile);
 457     return;
 458
 459 error:
 460     server.repl_state = REDIS_REPL_CONNECT;
 461     close(fd);
 462     return;
 463 }
 464
 465 int connectWithMaster(void) {
 466     int fd;
 467
 468     fd = anetTcpNonBlockConnect(NULL,server.masterhost,server.masterport);
 469     if (fd == -1) {
 470         redisLog(REDIS_WARNING,"Unable to connect to MASTER: %s",
 471             strerror(errno));
 472         return REDIS_ERR;
 473     }
 474
 475     if (aeCreateFileEvent(server.el,fd,AE_READABLE|AE_WRITABLE,syncWithMaster,NULL) ==
 476             AE_ERR)
 477     {
 478         close(fd);
 479         redisLog(REDIS_WARNING,"Can't create readable event for SYNC");
 480         return REDIS_ERR;
 481     }
 482
 483     server.repl_transfer_lastio = server.unixtime;
 484     server.repl_transfer_s = fd;
 485     server.repl_state = REDIS_REPL_CONNECTING;
 486     return REDIS_OK;
 487 }
 488
 489 /* This function can be called when a non blocking connection is currently
 490  * in progress to undo it. */
 491 void undoConnectWithMaster(void) {
 492     int fd = server.repl_transfer_s;
 493
 494     redisAssert(server.repl_state == REDIS_REPL_CONNECTING);
 495     aeDeleteFileEvent(server.el,fd,AE_READABLE|AE_WRITABLE);
 496     close(fd);
 497     server.repl_transfer_s = -1;
 498     server.repl_state = REDIS_REPL_CONNECT;
 499 }
 500
 501 void slaveofCommand(redisClient *c) {
 502     if (!strcasecmp(c->argv[1]->ptr,"no") &&
 503         !strcasecmp(c->argv[2]->ptr,"one")) {
 504         if (server.masterhost) {
 505             sdsfree(server.masterhost);
 506             server.masterhost = NULL;
 507             if (server.master) freeClient(server.master);
 508             if (server.repl_state == REDIS_REPL_TRANSFER)
 509                 replicationAbortSyncTransfer();
 510             else if (server.repl_state == REDIS_REPL_CONNECTING)
 511                 undoConnectWithMaster();
 512             server.repl_state = REDIS_REPL_NONE;
 513             redisLog(REDIS_NOTICE,"MASTER MODE enabled (user request)");
 514         }
 515     } else {
 516         long port;
 517
 518         if ((getLongFromObjectOrReply(c, c->argv[2], &port, NULL) != REDIS_OK))
 519             return;
 520
 521         /* Check if we are already attached to the specified slave */
 522         if (server.masterhost && !strcasecmp(server.masterhost,c->argv[1]->ptr)
 523             && server.masterport == port) {
 524             redisLog(REDIS_NOTICE,"SLAVE OF would result into synchronization with the master we are already connected with. No operation performed.");
 525             addReplySds(c,sdsnew("+OK Already connected to specified master\r\n"));
 526             return;
 527         }
 528         /* There was no previous master or the user specified a different one,
 529          * we can continue. */
 530         sdsfree(server.masterhost);
 531         server.masterhost = sdsdup(c->argv[1]->ptr);
 532         server.masterport = port;
 533         if (server.master) freeClient(server.master);
 534         disconnectSlaves(); /* Force our slaves to resync with us as well. */
 535         if (server.repl_state == REDIS_REPL_TRANSFER)
 536             replicationAbortSyncTransfer();
 537         server.repl_state = REDIS_REPL_CONNECT;
 538         redisLog(REDIS_NOTICE,"SLAVE OF %s:%d enabled (user request)",
 539             server.masterhost, server.masterport);
 540     }
 541     addReply(c,shared.ok);
 542 }
 543
 544 /* --------------------------- REPLICATION CRON  ---------------------------- */
 545
 546 void replicationCron(void) {
 547     /* Non blocking connection timeout? */
 548     if (server.masterhost && server.repl_state == REDIS_REPL_CONNECTING &&
 549         (time(NULL)-server.repl_transfer_lastio) > server.repl_timeout)
 550     {
 551         redisLog(REDIS_WARNING,"Timeout connecting to the MASTER...");
 552         undoConnectWithMaster();
 553     }
 554
 555     /* Bulk transfer I/O timeout? */
 556     if (server.masterhost && server.repl_state == REDIS_REPL_TRANSFER &&
 557         (time(NULL)-server.repl_transfer_lastio) > server.repl_timeout)
 558     {
 559         redisLog(REDIS_WARNING,"Timeout receiving bulk data from MASTER...");
 560         replicationAbortSyncTransfer();
 561     }
 562
 563     /* Timed out master when we are an already connected slave? */
 564     if (server.masterhost && server.repl_state == REDIS_REPL_CONNECTED &&
 565         (time(NULL)-server.master->lastinteraction) > server.repl_timeout)
 566     {
 567         redisLog(REDIS_WARNING,"MASTER time out: no data nor PING received...");
 568         freeClient(server.master);
 569     }
 570
 571     /* Check if we should connect to a MASTER */
 572     if (server.repl_state == REDIS_REPL_CONNECT) {
 573         redisLog(REDIS_NOTICE,"Connecting to MASTER...");
 574         if (connectWithMaster() == REDIS_OK) {
 575             redisLog(REDIS_NOTICE,"MASTER <-> SLAVE sync started");
 576         }
 577     }
 578
 579     /* If we have attached slaves, PING them from time to time.
 580      * So slaves can implement an explicit timeout to masters, and will
 581      * be able to detect a link disconnection even if the TCP connection
 582      * will not actually go down. */
 583     if (!(server.cronloops % (server.repl_ping_slave_period*10))) {
 584         listIter li;
 585         listNode *ln;
 586
 587         listRewind(server.slaves,&li);
 588         while((ln = listNext(&li))) {
 589             redisClient *slave = ln->value;
 590
 591             /* Don't ping slaves that are in the middle of a bulk transfer
 592              * with the master for first synchronization. */
 593             if (slave->replstate == REDIS_REPL_SEND_BULK) continue;
 594             if (slave->replstate == REDIS_REPL_ONLINE) {
 595                 /* If the slave is online send a normal ping */
 596                 addReplySds(slave,sdsnew("*1\r\n$4\r\nPING\r\n"));
 597             } else {
 598                 /* Otherwise we are in the pre-synchronization stage.
 599                  * Just a newline will do the work of refreshing the
 600                  * connection last interaction time, and at the same time
 601                  * we'll be sure that being a single char there are no
 602                  * short-write problems. */
 603                 if (write(slave->fd, "\n", 1) == -1) {
 604                     /* Don't worry, it's just a ping. */
 605                 }
 606             }
 607         }
 608     }
 609 }