X-Git-Url: https://git.saurik.com/redis.git/blobdiff_plain/5171777bf112a6a930c4750949037ce741f3bf28..1858da2faae3b6a8becf4f7eef3f712d6e4b986b:/src/replication.c diff --git a/src/replication.c b/src/replication.c index 8c629006..f03c424f 100644 --- a/src/replication.c +++ b/src/replication.c @@ -5,41 +5,13 @@ #include #include +/* ---------------------------------- MASTER -------------------------------- */ + void replicationFeedSlaves(list *slaves, int dictid, robj **argv, int argc) { listNode *ln; listIter li; - int outc = 0, j; - robj **outv; - /* We need 1+(ARGS*3) objects since commands are using the new protocol - * and we one 1 object for the first "*\r\n" multibulk count, then - * for every additional object we have "$\r\n" + object + "\r\n". */ - robj *static_outv[REDIS_STATIC_ARGS*3+1]; - robj *lenobj; - - if (argc <= REDIS_STATIC_ARGS) { - outv = static_outv; - } else { - outv = zmalloc(sizeof(robj*)*(argc*3+1)); - } - - lenobj = createObject(REDIS_STRING, - sdscatprintf(sdsempty(), "*%d\r\n", argc)); - lenobj->refcount = 0; - outv[outc++] = lenobj; - for (j = 0; j < argc; j++) { - lenobj = createObject(REDIS_STRING, - sdscatprintf(sdsempty(),"$%lu\r\n", - (unsigned long) stringObjectLen(argv[j]))); - lenobj->refcount = 0; - outv[outc++] = lenobj; - outv[outc++] = argv[j]; - outv[outc++] = shared.crlf; - } + int j; - /* Increment all the refcounts at start and decrement at end in order to - * be sure to free objects if there is no slave in a replication state - * able to be feed with commands */ - for (j = 0; j < outc; j++) incrRefCount(outv[j]); listRewind(slaves,&li); while((ln = listNext(&li))) { redisClient *slave = ln->value; @@ -47,47 +19,45 @@ void replicationFeedSlaves(list *slaves, int dictid, robj **argv, int argc) { /* Don't feed slaves that are still waiting for BGSAVE to start */ if (slave->replstate == REDIS_REPL_WAIT_BGSAVE_START) continue; - /* Feed all the other slaves, MONITORs and so on */ + /* Feed slaves that are waiting for the initial SYNC (so these commands + * are queued in the output buffer until the intial SYNC completes), + * or are already in sync with the master. */ if (slave->slaveseldb != dictid) { robj *selectcmd; - switch(dictid) { - case 0: selectcmd = shared.select0; break; - case 1: selectcmd = shared.select1; break; - case 2: selectcmd = shared.select2; break; - case 3: selectcmd = shared.select3; break; - case 4: selectcmd = shared.select4; break; - case 5: selectcmd = shared.select5; break; - case 6: selectcmd = shared.select6; break; - case 7: selectcmd = shared.select7; break; - case 8: selectcmd = shared.select8; break; - case 9: selectcmd = shared.select9; break; - default: + if (dictid >= 0 && dictid < REDIS_SHARED_SELECT_CMDS) { + selectcmd = shared.select[dictid]; + incrRefCount(selectcmd); + } else { selectcmd = createObject(REDIS_STRING, sdscatprintf(sdsempty(),"select %d\r\n",dictid)); - selectcmd->refcount = 0; - break; } addReply(slave,selectcmd); + decrRefCount(selectcmd); slave->slaveseldb = dictid; } - for (j = 0; j < outc; j++) addReply(slave,outv[j]); + addReplyMultiBulkLen(slave,argc); + for (j = 0; j < argc; j++) addReplyBulk(slave,argv[j]); } - for (j = 0; j < outc; j++) decrRefCount(outv[j]); - if (outv != static_outv) zfree(outv); } -void replicationFeedMonitors(list *monitors, int dictid, robj **argv, int argc) { +void replicationFeedMonitors(redisClient *c, list *monitors, int dictid, robj **argv, int argc) { listNode *ln; listIter li; - int j; + int j, port; sds cmdrepr = sdsnew("+"); robj *cmdobj; + char ip[32]; struct timeval tv; gettimeofday(&tv,NULL); - cmdrepr = sdscatprintf(cmdrepr,"%ld.%ld ",(long)tv.tv_sec,(long)tv.tv_usec); - if (dictid != 0) cmdrepr = sdscatprintf(cmdrepr,"(db %d) ", dictid); + cmdrepr = sdscatprintf(cmdrepr,"%ld.%06ld ",(long)tv.tv_sec,(long)tv.tv_usec); + if (c->flags & REDIS_LUA_CLIENT) { + cmdrepr = sdscatprintf(cmdrepr,"[%d lua] ", dictid); + } else { + anetPeerToString(c->fd,ip,&port); + cmdrepr = sdscatprintf(cmdrepr,"[%d %s:%d] ", dictid,ip,port); + } for (j = 0; j < argc; j++) { if (argv[j]->encoding == REDIS_ENCODING_INT) { @@ -110,75 +80,13 @@ void replicationFeedMonitors(list *monitors, int dictid, robj **argv, int argc) decrRefCount(cmdobj); } -int syncWrite(int fd, char *ptr, ssize_t size, int timeout) { - ssize_t nwritten, ret = size; - time_t start = time(NULL); - - timeout++; - while(size) { - if (aeWait(fd,AE_WRITABLE,1000) & AE_WRITABLE) { - nwritten = write(fd,ptr,size); - if (nwritten == -1) return -1; - ptr += nwritten; - size -= nwritten; - } - if ((time(NULL)-start) > timeout) { - errno = ETIMEDOUT; - return -1; - } - } - return ret; -} - -int syncRead(int fd, char *ptr, ssize_t size, int timeout) { - ssize_t nread, totread = 0; - time_t start = time(NULL); - - timeout++; - while(size) { - if (aeWait(fd,AE_READABLE,1000) & AE_READABLE) { - nread = read(fd,ptr,size); - if (nread <= 0) return -1; - ptr += nread; - size -= nread; - totread += nread; - } - if ((time(NULL)-start) > timeout) { - errno = ETIMEDOUT; - return -1; - } - } - return totread; -} - -int syncReadLine(int fd, char *ptr, ssize_t size, int timeout) { - ssize_t nread = 0; - - size--; - while(size) { - char c; - - if (syncRead(fd,&c,1,timeout) == -1) return -1; - if (c == '\n') { - *ptr = '\0'; - if (nread && *(ptr-1) == '\r') *(ptr-1) = '\0'; - return nread; - } else { - *ptr++ = c; - *ptr = '\0'; - nread++; - } - } - return nread; -} - void syncCommand(redisClient *c) { /* ignore SYNC if aleady slave or in monitor mode */ if (c->flags & REDIS_SLAVE) return; /* Refuse SYNC requests if we are a slave but the link with our master * is not ok... */ - if (server.masterhost && server.replstate != REDIS_REPL_CONNECTED) { + if (server.masterhost && server.repl_state != REDIS_REPL_CONNECTED) { addReplyError(c,"Can't SYNC while not connected with my master"); return; } @@ -195,7 +103,7 @@ void syncCommand(redisClient *c) { redisLog(REDIS_NOTICE,"Slave ask for synchronization"); /* Here we need to check if there is a background saving operation * in progress, or if it is required to start one */ - if (server.bgsavechildpid != -1) { + if (server.rdb_child_pid != -1) { /* Ok a background save is in progress. Let's check if it is a good * one for replication, i.e. if there is another slave that is * registering differences since the server forked to save */ @@ -211,8 +119,7 @@ void syncCommand(redisClient *c) { if (ln) { /* Perfect, the server is already registering differences for * another slave. Set the right state, and copy the buffer. */ - listRelease(c->reply); - c->reply = listDup(slave->reply); + copyClientOutputBuffer(c,slave); c->replstate = REDIS_REPL_WAIT_BGSAVE_END; redisLog(REDIS_NOTICE,"Waiting for end of BGSAVE for SYNC"); } else { @@ -224,7 +131,7 @@ void syncCommand(redisClient *c) { } else { /* Ok we don't have a BGSAVE in progress, let's start one */ redisLog(REDIS_NOTICE,"Starting BGSAVE for SYNC"); - if (rdbSaveBackground(server.dbfilename) != REDIS_OK) { + if (rdbSaveBackground(server.rdb_filename) != REDIS_OK) { redisLog(REDIS_NOTICE,"Replication failed, can't BGSAVE"); addReplyError(c,"Unable to perform background save"); return; @@ -318,7 +225,7 @@ void updateSlavesWaitingBgsave(int bgsaveerr) { redisLog(REDIS_WARNING,"SYNC failed. BGSAVE child returned an error"); continue; } - if ((slave->repldbfd = open(server.dbfilename,O_RDONLY)) == -1 || + if ((slave->repldbfd = open(server.rdb_filename,O_RDONLY)) == -1 || redis_fstat(slave->repldbfd,&buf) == -1) { freeClient(slave); redisLog(REDIS_WARNING,"SYNC failed. Can't open/stat DB after BGSAVE: %s", strerror(errno)); @@ -335,7 +242,7 @@ void updateSlavesWaitingBgsave(int bgsaveerr) { } } if (startbgsave) { - if (rdbSaveBackground(server.dbfilename) != REDIS_OK) { + if (rdbSaveBackground(server.rdb_filename) != REDIS_OK) { listIter li; listRewind(server.slaves,&li); @@ -350,120 +257,248 @@ void updateSlavesWaitingBgsave(int bgsaveerr) { } } -int syncWithMaster(void) { - char buf[1024], tmpfile[256], authcmd[1024]; - long dumpsize; - int fd = anetTcpConnect(NULL,server.masterhost,server.masterport); +/* ----------------------------------- SLAVE -------------------------------- */ + +/* Abort the async download of the bulk dataset while SYNC-ing with master */ +void replicationAbortSyncTransfer(void) { + redisAssert(server.repl_state == REDIS_REPL_TRANSFER); + + aeDeleteFileEvent(server.el,server.repl_transfer_s,AE_READABLE); + close(server.repl_transfer_s); + close(server.repl_transfer_fd); + unlink(server.repl_transfer_tmpfile); + zfree(server.repl_transfer_tmpfile); + server.repl_state = REDIS_REPL_CONNECT; +} + +/* Asynchronously read the SYNC payload we receive from a master */ +void readSyncBulkPayload(aeEventLoop *el, int fd, void *privdata, int mask) { + char buf[4096]; + ssize_t nread, readlen; + REDIS_NOTUSED(el); + REDIS_NOTUSED(privdata); + REDIS_NOTUSED(mask); + + /* If repl_transfer_left == -1 we still have to read the bulk length + * from the master reply. */ + if (server.repl_transfer_left == -1) { + if (syncReadLine(fd,buf,1024,server.repl_syncio_timeout*1000) == -1) { + redisLog(REDIS_WARNING, + "I/O error reading bulk count from MASTER: %s", + strerror(errno)); + goto error; + } + + if (buf[0] == '-') { + redisLog(REDIS_WARNING, + "MASTER aborted replication with an error: %s", + buf+1); + goto error; + } else if (buf[0] == '\0') { + /* At this stage just a newline works as a PING in order to take + * the connection live. So we refresh our last interaction + * timestamp. */ + server.repl_transfer_lastio = server.unixtime; + return; + } else if (buf[0] != '$') { + redisLog(REDIS_WARNING,"Bad protocol from MASTER, the first byte is not '$', are you sure the host and port are right?"); + goto error; + } + server.repl_transfer_left = strtol(buf+1,NULL,10); + redisLog(REDIS_NOTICE, + "MASTER <-> SLAVE sync: receiving %ld bytes from master", + server.repl_transfer_left); + return; + } + + /* Read bulk data */ + readlen = (server.repl_transfer_left < (signed)sizeof(buf)) ? + server.repl_transfer_left : (signed)sizeof(buf); + nread = read(fd,buf,readlen); + if (nread <= 0) { + redisLog(REDIS_WARNING,"I/O error trying to sync with MASTER: %s", + (nread == -1) ? strerror(errno) : "connection lost"); + replicationAbortSyncTransfer(); + return; + } + server.repl_transfer_lastio = server.unixtime; + if (write(server.repl_transfer_fd,buf,nread) != nread) { + redisLog(REDIS_WARNING,"Write error or short write writing to the DB dump file needed for MASTER <-> SLAVE synchronization: %s", strerror(errno)); + goto error; + } + server.repl_transfer_left -= nread; + /* Check if the transfer is now complete */ + if (server.repl_transfer_left == 0) { + if (rename(server.repl_transfer_tmpfile,server.rdb_filename) == -1) { + redisLog(REDIS_WARNING,"Failed trying to rename the temp DB into dump.rdb in MASTER <-> SLAVE synchronization: %s", strerror(errno)); + replicationAbortSyncTransfer(); + return; + } + redisLog(REDIS_NOTICE, "MASTER <-> SLAVE sync: Loading DB in memory"); + emptyDb(); + /* Before loading the DB into memory we need to delete the readable + * handler, otherwise it will get called recursively since + * rdbLoad() will call the event loop to process events from time to + * time for non blocking loading. */ + aeDeleteFileEvent(server.el,server.repl_transfer_s,AE_READABLE); + if (rdbLoad(server.rdb_filename) != REDIS_OK) { + redisLog(REDIS_WARNING,"Failed trying to load the MASTER synchronization DB from disk"); + replicationAbortSyncTransfer(); + return; + } + /* Final setup of the connected slave <- master link */ + zfree(server.repl_transfer_tmpfile); + close(server.repl_transfer_fd); + server.master = createClient(server.repl_transfer_s); + server.master->flags |= REDIS_MASTER; + server.master->authenticated = 1; + server.repl_state = REDIS_REPL_CONNECTED; + redisLog(REDIS_NOTICE, "MASTER <-> SLAVE sync: Finished with success"); + /* Restart the AOF subsystem now that we finished the sync. This + * will trigger an AOF rewrite, and when done will start appending + * to the new file. */ + if (server.aof_state != REDIS_AOF_OFF) { + int retry = 10; + + stopAppendOnly(); + while (retry-- && startAppendOnly() == REDIS_ERR) { + redisLog(REDIS_WARNING,"Failed enabling the AOF after successful master synchrnization! Trying it again in one second."); + sleep(1); + } + if (!retry) { + redisLog(REDIS_WARNING,"FATAL: this slave instance finished the synchronization with its master, but the AOF can't be turned on. Exiting now."); + exit(1); + } + } + } + + return; + +error: + replicationAbortSyncTransfer(); + return; +} + +void syncWithMaster(aeEventLoop *el, int fd, void *privdata, int mask) { + char buf[1024], tmpfile[256]; int dfd, maxtries = 5; + REDIS_NOTUSED(el); + REDIS_NOTUSED(privdata); + REDIS_NOTUSED(mask); - if (fd == -1) { - redisLog(REDIS_WARNING,"Unable to connect to MASTER: %s", - strerror(errno)); - return REDIS_ERR; + /* If this event fired after the user turned the instance into a master + * with SLAVEOF NO ONE we must just return ASAP. */ + if (server.repl_state == REDIS_REPL_NONE) { + close(fd); + return; } + redisLog(REDIS_NOTICE,"Non blocking connect for SYNC fired the event."); + /* This event should only be triggered once since it is used to have a + * non-blocking connect(2) to the master. It has been triggered when this + * function is called, so we can delete it. */ + aeDeleteFileEvent(server.el,fd,AE_READABLE|AE_WRITABLE); + /* AUTH with the master if required. */ if(server.masterauth) { - snprintf(authcmd, 1024, "AUTH %s\r\n", server.masterauth); - if (syncWrite(fd, authcmd, strlen(server.masterauth)+7, 5) == -1) { - close(fd); + char authcmd[1024]; + size_t authlen; + + authlen = snprintf(authcmd,sizeof(authcmd),"AUTH %s\r\n",server.masterauth); + if (syncWrite(fd,authcmd,authlen,server.repl_syncio_timeout*1000) == -1) { redisLog(REDIS_WARNING,"Unable to AUTH to MASTER: %s", strerror(errno)); - return REDIS_ERR; - } + goto error; + } /* Read the AUTH result. */ - if (syncReadLine(fd,buf,1024,3600) == -1) { - close(fd); + if (syncReadLine(fd,buf,1024,server.repl_syncio_timeout*1000) == -1) { redisLog(REDIS_WARNING,"I/O error reading auth result from MASTER: %s", strerror(errno)); - return REDIS_ERR; + goto error; } if (buf[0] != '+') { - close(fd); redisLog(REDIS_WARNING,"Cannot AUTH to MASTER, is the masterauth password correct?"); - return REDIS_ERR; + goto error; } } /* Issue the SYNC command */ - if (syncWrite(fd,"SYNC \r\n",7,5) == -1) { - close(fd); + if (syncWrite(fd,"SYNC \r\n",7,server.repl_syncio_timeout*1000) == -1) { redisLog(REDIS_WARNING,"I/O error writing to MASTER: %s", strerror(errno)); - return REDIS_ERR; - } - /* Read the bulk write count */ - if (syncReadLine(fd,buf,1024,3600) == -1) { - close(fd); - redisLog(REDIS_WARNING,"I/O error reading bulk count from MASTER: %s", - strerror(errno)); - return REDIS_ERR; - } - if (buf[0] == '-') { - close(fd); - redisLog(REDIS_WARNING,"MASTER aborted replication with an error: %s", - buf+1); - return REDIS_ERR; - } else if (buf[0] != '$') { - close(fd); - redisLog(REDIS_WARNING,"Bad protocol from MASTER, the first byte is not '$', are you sure the host and port are right?"); - return REDIS_ERR; + goto error; } - dumpsize = strtol(buf+1,NULL,10); - redisLog(REDIS_NOTICE,"Receiving %ld bytes data dump from MASTER",dumpsize); - /* Read the bulk write data on a temp file */ + + /* Prepare a suitable temp file for bulk transfer */ while(maxtries--) { snprintf(tmpfile,256, - "temp-%d.%ld.rdb",(int)time(NULL),(long int)getpid()); + "temp-%d.%ld.rdb",(int)server.unixtime,(long int)getpid()); dfd = open(tmpfile,O_CREAT|O_WRONLY|O_EXCL,0644); if (dfd != -1) break; sleep(1); } if (dfd == -1) { - close(fd); redisLog(REDIS_WARNING,"Opening the temp file needed for MASTER <-> SLAVE synchronization: %s",strerror(errno)); - return REDIS_ERR; + goto error; } - while(dumpsize) { - int nread, nwritten; - - nread = read(fd,buf,(dumpsize < 1024)?dumpsize:1024); - if (nread <= 0) { - redisLog(REDIS_WARNING,"I/O error trying to sync with MASTER: %s", - (nread == -1) ? strerror(errno) : "connection lost"); - close(fd); - close(dfd); - return REDIS_ERR; - } - nwritten = write(dfd,buf,nread); - if (nwritten == -1) { - redisLog(REDIS_WARNING,"Write error writing to the DB dump file needed for MASTER <-> SLAVE synchrnonization: %s", strerror(errno)); - close(fd); - close(dfd); - return REDIS_ERR; - } - dumpsize -= nread; + + /* Setup the non blocking download of the bulk file. */ + if (aeCreateFileEvent(server.el,fd, AE_READABLE,readSyncBulkPayload,NULL) + == AE_ERR) + { + redisLog(REDIS_WARNING,"Can't create readable event for SYNC"); + goto error; } - close(dfd); - if (rename(tmpfile,server.dbfilename) == -1) { - redisLog(REDIS_WARNING,"Failed trying to rename the temp DB into dump.rdb in MASTER <-> SLAVE synchronization: %s", strerror(errno)); - unlink(tmpfile); - close(fd); + + server.repl_state = REDIS_REPL_TRANSFER; + server.repl_transfer_left = -1; + server.repl_transfer_fd = dfd; + server.repl_transfer_lastio = server.unixtime; + server.repl_transfer_tmpfile = zstrdup(tmpfile); + return; + +error: + server.repl_state = REDIS_REPL_CONNECT; + close(fd); + return; +} + +int connectWithMaster(void) { + int fd; + + fd = anetTcpNonBlockConnect(NULL,server.masterhost,server.masterport); + if (fd == -1) { + redisLog(REDIS_WARNING,"Unable to connect to MASTER: %s", + strerror(errno)); return REDIS_ERR; } - emptyDb(); - if (rdbLoad(server.dbfilename) != REDIS_OK) { - redisLog(REDIS_WARNING,"Failed trying to load the MASTER synchronization DB from disk"); + + if (aeCreateFileEvent(server.el,fd,AE_READABLE|AE_WRITABLE,syncWithMaster,NULL) == + AE_ERR) + { close(fd); + redisLog(REDIS_WARNING,"Can't create readable event for SYNC"); return REDIS_ERR; } - server.master = createClient(fd); - server.master->flags |= REDIS_MASTER; - server.master->authenticated = 1; - server.replstate = REDIS_REPL_CONNECTED; + + server.repl_transfer_lastio = server.unixtime; + server.repl_transfer_s = fd; + server.repl_state = REDIS_REPL_CONNECTING; return REDIS_OK; } +/* This function can be called when a non blocking connection is currently + * in progress to undo it. */ +void undoConnectWithMaster(void) { + int fd = server.repl_transfer_s; + + redisAssert(server.repl_state == REDIS_REPL_CONNECTING); + aeDeleteFileEvent(server.el,fd,AE_READABLE|AE_WRITABLE); + close(fd); + server.repl_transfer_s = -1; + server.repl_state = REDIS_REPL_CONNECT; +} + void slaveofCommand(redisClient *c) { if (!strcasecmp(c->argv[1]->ptr,"no") && !strcasecmp(c->argv[2]->ptr,"one")) { @@ -471,17 +506,105 @@ void slaveofCommand(redisClient *c) { sdsfree(server.masterhost); server.masterhost = NULL; if (server.master) freeClient(server.master); - server.replstate = REDIS_REPL_NONE; + if (server.repl_state == REDIS_REPL_TRANSFER) + replicationAbortSyncTransfer(); + else if (server.repl_state == REDIS_REPL_CONNECTING) + undoConnectWithMaster(); + server.repl_state = REDIS_REPL_NONE; redisLog(REDIS_NOTICE,"MASTER MODE enabled (user request)"); } } else { + long port; + + if ((getLongFromObjectOrReply(c, c->argv[2], &port, NULL) != REDIS_OK)) + return; + + /* Check if we are already attached to the specified slave */ + if (server.masterhost && !strcasecmp(server.masterhost,c->argv[1]->ptr) + && server.masterport == port) { + redisLog(REDIS_NOTICE,"SLAVE OF would result into synchronization with the master we are already connected with. No operation performed."); + addReplySds(c,sdsnew("+OK Already connected to specified master\r\n")); + return; + } + /* There was no previous master or the user specified a different one, + * we can continue. */ sdsfree(server.masterhost); server.masterhost = sdsdup(c->argv[1]->ptr); - server.masterport = atoi(c->argv[2]->ptr); + server.masterport = port; if (server.master) freeClient(server.master); - server.replstate = REDIS_REPL_CONNECT; + disconnectSlaves(); /* Force our slaves to resync with us as well. */ + if (server.repl_state == REDIS_REPL_TRANSFER) + replicationAbortSyncTransfer(); + server.repl_state = REDIS_REPL_CONNECT; redisLog(REDIS_NOTICE,"SLAVE OF %s:%d enabled (user request)", server.masterhost, server.masterport); } addReply(c,shared.ok); } + +/* --------------------------- REPLICATION CRON ---------------------------- */ + +void replicationCron(void) { + /* Non blocking connection timeout? */ + if (server.masterhost && server.repl_state == REDIS_REPL_CONNECTING && + (time(NULL)-server.repl_transfer_lastio) > server.repl_timeout) + { + redisLog(REDIS_WARNING,"Timeout connecting to the MASTER..."); + undoConnectWithMaster(); + } + + /* Bulk transfer I/O timeout? */ + if (server.masterhost && server.repl_state == REDIS_REPL_TRANSFER && + (time(NULL)-server.repl_transfer_lastio) > server.repl_timeout) + { + redisLog(REDIS_WARNING,"Timeout receiving bulk data from MASTER..."); + replicationAbortSyncTransfer(); + } + + /* Timed out master when we are an already connected slave? */ + if (server.masterhost && server.repl_state == REDIS_REPL_CONNECTED && + (time(NULL)-server.master->lastinteraction) > server.repl_timeout) + { + redisLog(REDIS_WARNING,"MASTER time out: no data nor PING received..."); + freeClient(server.master); + } + + /* Check if we should connect to a MASTER */ + if (server.repl_state == REDIS_REPL_CONNECT) { + redisLog(REDIS_NOTICE,"Connecting to MASTER..."); + if (connectWithMaster() == REDIS_OK) { + redisLog(REDIS_NOTICE,"MASTER <-> SLAVE sync started"); + } + } + + /* If we have attached slaves, PING them from time to time. + * So slaves can implement an explicit timeout to masters, and will + * be able to detect a link disconnection even if the TCP connection + * will not actually go down. */ + if (!(server.cronloops % (server.repl_ping_slave_period*10))) { + listIter li; + listNode *ln; + + listRewind(server.slaves,&li); + while((ln = listNext(&li))) { + redisClient *slave = ln->value; + + /* Don't ping slaves that are in the middle of a bulk transfer + * with the master for first synchronization. */ + if (slave->replstate == REDIS_REPL_SEND_BULK) continue; + if (slave->replstate == REDIS_REPL_ONLINE) { + /* If the slave is online send a normal ping */ + addReplySds(slave,sdsnew("*1\r\n$4\r\nPING\r\n")); + } else { + /* Otherwise we are in the pre-synchronization stage. + * Just a newline will do the work of refreshing the + * connection last interaction time, and at the same time + * we'll be sure that being a single char there are no + * short-write problems. */ + if (write(slave->fd, "\n", 1) == -1) { + /* Don't worry, it's just a ping. */ + } + } + } + } +}