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redict/src/replication.c

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#include "redis.h"
#include <sys/time.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>
/* ---------------------------------- MASTER -------------------------------- */
void replicationFeedSlaves(list *slaves, int dictid, robj **argv, int argc) {
listNode *ln;
listIter li;
int j;
listRewind(slaves,&li);
while((ln = listNext(&li))) {
redisClient *slave = ln->value;
/* Don't feed slaves that are still waiting for BGSAVE to start */
if (slave->replstate == REDIS_REPL_WAIT_BGSAVE_START) continue;
/* 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:
selectcmd = createObject(REDIS_STRING,
sdscatprintf(sdsempty(),"select %d\r\n",dictid));
selectcmd->refcount = 0;
break;
}
addReply(slave,selectcmd);
slave->slaveseldb = dictid;
}
addReplyMultiBulkLen(slave,argc);
for (j = 0; j < argc; j++) addReplyBulk(slave,argv[j]);
}
}
void replicationFeedMonitors(list *monitors, int dictid, robj **argv, int argc) {
listNode *ln;
listIter li;
int j;
sds cmdrepr = sdsnew("+");
robj *cmdobj;
struct timeval tv;
gettimeofday(&tv,NULL);
cmdrepr = sdscatprintf(cmdrepr,"%ld.%06ld ",(long)tv.tv_sec,(long)tv.tv_usec);
if (dictid != 0) cmdrepr = sdscatprintf(cmdrepr,"(db %d) ", dictid);
for (j = 0; j < argc; j++) {
if (argv[j]->encoding == REDIS_ENCODING_INT) {
cmdrepr = sdscatprintf(cmdrepr, "\"%ld\"", (long)argv[j]->ptr);
} else {
cmdrepr = sdscatrepr(cmdrepr,(char*)argv[j]->ptr,
sdslen(argv[j]->ptr));
}
if (j != argc-1)
cmdrepr = sdscatlen(cmdrepr," ",1);
}
cmdrepr = sdscatlen(cmdrepr,"\r\n",2);
cmdobj = createObject(REDIS_STRING,cmdrepr);
listRewind(monitors,&li);
while((ln = listNext(&li))) {
redisClient *monitor = ln->value;
addReply(monitor,cmdobj);
}
decrRefCount(cmdobj);
}
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.repl_state != REDIS_REPL_CONNECTED) {
addReplyError(c,"Can't SYNC while not connected with my master");
return;
}
/* SYNC can't be issued when the server has pending data to send to
* the client about already issued commands. We need a fresh reply
* buffer registering the differences between the BGSAVE and the current
* dataset, so that we can copy to other slaves if needed. */
if (listLength(c->reply) != 0) {
addReplyError(c,"SYNC is invalid with pending input");
return;
}
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.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 */
redisClient *slave;
listNode *ln;
listIter li;
listRewind(server.slaves,&li);
while((ln = listNext(&li))) {
slave = ln->value;
if (slave->replstate == REDIS_REPL_WAIT_BGSAVE_END) break;
}
if (ln) {
/* Perfect, the server is already registering differences for
* another slave. Set the right state, and copy the buffer. */
copyClientOutputBuffer(c,slave);
c->replstate = REDIS_REPL_WAIT_BGSAVE_END;
redisLog(REDIS_NOTICE,"Waiting for end of BGSAVE for SYNC");
} else {
/* No way, we need to wait for the next BGSAVE in order to
* register differences */
c->replstate = REDIS_REPL_WAIT_BGSAVE_START;
redisLog(REDIS_NOTICE,"Waiting for next BGSAVE for SYNC");
}
} else {
/* Ok we don't have a BGSAVE in progress, let's start one */
redisLog(REDIS_NOTICE,"Starting BGSAVE for SYNC");
if (rdbSaveBackground(server.rdb_filename) != REDIS_OK) {
redisLog(REDIS_NOTICE,"Replication failed, can't BGSAVE");
addReplyError(c,"Unable to perform background save");
return;
}
c->replstate = REDIS_REPL_WAIT_BGSAVE_END;
}
c->repldbfd = -1;
c->flags |= REDIS_SLAVE;
c->slaveseldb = 0;
listAddNodeTail(server.slaves,c);
return;
}
void sendBulkToSlave(aeEventLoop *el, int fd, void *privdata, int mask) {
redisClient *slave = privdata;
REDIS_NOTUSED(el);
REDIS_NOTUSED(mask);
char buf[REDIS_IOBUF_LEN];
ssize_t nwritten, buflen;
if (slave->repldboff == 0) {
/* Write the bulk write count before to transfer the DB. In theory here
* we don't know how much room there is in the output buffer of the
* socket, but in pratice SO_SNDLOWAT (the minimum count for output
* operations) will never be smaller than the few bytes we need. */
sds bulkcount;
bulkcount = sdscatprintf(sdsempty(),"$%lld\r\n",(unsigned long long)
slave->repldbsize);
if (write(fd,bulkcount,sdslen(bulkcount)) != (signed)sdslen(bulkcount))
{
sdsfree(bulkcount);
freeClient(slave);
return;
}
sdsfree(bulkcount);
}
lseek(slave->repldbfd,slave->repldboff,SEEK_SET);
buflen = read(slave->repldbfd,buf,REDIS_IOBUF_LEN);
if (buflen <= 0) {
redisLog(REDIS_WARNING,"Read error sending DB to slave: %s",
(buflen == 0) ? "premature EOF" : strerror(errno));
freeClient(slave);
return;
}
if ((nwritten = write(fd,buf,buflen)) == -1) {
redisLog(REDIS_VERBOSE,"Write error sending DB to slave: %s",
strerror(errno));
freeClient(slave);
return;
}
slave->repldboff += nwritten;
if (slave->repldboff == slave->repldbsize) {
close(slave->repldbfd);
slave->repldbfd = -1;
aeDeleteFileEvent(server.el,slave->fd,AE_WRITABLE);
slave->replstate = REDIS_REPL_ONLINE;
if (aeCreateFileEvent(server.el, slave->fd, AE_WRITABLE,
sendReplyToClient, slave) == AE_ERR) {
freeClient(slave);
return;
}
addReplySds(slave,sdsempty());
redisLog(REDIS_NOTICE,"Synchronization with slave succeeded");
}
}
/* This function is called at the end of every backgrond saving.
* The argument bgsaveerr is REDIS_OK if the background saving succeeded
* otherwise REDIS_ERR is passed to the function.
*
* The goal of this function is to handle slaves waiting for a successful
* background saving in order to perform non-blocking synchronization. */
void updateSlavesWaitingBgsave(int bgsaveerr) {
listNode *ln;
int startbgsave = 0;
listIter li;
listRewind(server.slaves,&li);
while((ln = listNext(&li))) {
redisClient *slave = ln->value;
if (slave->replstate == REDIS_REPL_WAIT_BGSAVE_START) {
startbgsave = 1;
slave->replstate = REDIS_REPL_WAIT_BGSAVE_END;
} else if (slave->replstate == REDIS_REPL_WAIT_BGSAVE_END) {
struct redis_stat buf;
if (bgsaveerr != REDIS_OK) {
freeClient(slave);
redisLog(REDIS_WARNING,"SYNC failed. BGSAVE child returned an error");
continue;
}
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));
continue;
}
slave->repldboff = 0;
slave->repldbsize = buf.st_size;
slave->replstate = REDIS_REPL_SEND_BULK;
aeDeleteFileEvent(server.el,slave->fd,AE_WRITABLE);
if (aeCreateFileEvent(server.el, slave->fd, AE_WRITABLE, sendBulkToSlave, slave) == AE_ERR) {
freeClient(slave);
continue;
}
}
}
if (startbgsave) {
if (rdbSaveBackground(server.rdb_filename) != REDIS_OK) {
listIter li;
listRewind(server.slaves,&li);
redisLog(REDIS_WARNING,"SYNC failed. BGSAVE failed");
while((ln = listNext(&li))) {
redisClient *slave = ln->value;
if (slave->replstate == REDIS_REPL_WAIT_BGSAVE_START)
freeClient(slave);
}
}
}
}
/* ----------------------------------- 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) == -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 = time(NULL);
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 = time(NULL);
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 synchrnonization: %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 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) {
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) == -1) {
redisLog(REDIS_WARNING,"Unable to AUTH to MASTER: %s",
strerror(errno));
goto error;
}
/* Read the AUTH result. */
if (syncReadLine(fd,buf,1024,server.repl_syncio_timeout) == -1) {
redisLog(REDIS_WARNING,"I/O error reading auth result from MASTER: %s",
strerror(errno));
goto error;
}
if (buf[0] != '+') {
redisLog(REDIS_WARNING,"Cannot AUTH to MASTER, is the masterauth password correct?");
goto error;
}
}
/* Issue the SYNC command */
if (syncWrite(fd,"SYNC \r\n",7,server.repl_syncio_timeout) == -1) {
redisLog(REDIS_WARNING,"I/O error writing to MASTER: %s",
strerror(errno));
goto error;
}
/* Prepare a suitable temp file for bulk transfer */
while(maxtries--) {
snprintf(tmpfile,256,
"temp-%d.%ld.rdb",(int)time(NULL),(long int)getpid());
dfd = open(tmpfile,O_CREAT|O_WRONLY|O_EXCL,0644);
if (dfd != -1) break;
sleep(1);
}
if (dfd == -1) {
redisLog(REDIS_WARNING,"Opening the temp file needed for MASTER <-> SLAVE synchronization: %s",strerror(errno));
goto error;
}
/* 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;
}
server.repl_state = REDIS_REPL_TRANSFER;
server.repl_transfer_left = -1;
server.repl_transfer_fd = dfd;
server.repl_transfer_lastio = time(NULL);
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;
}
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.repl_transfer_lastio = time(NULL);
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")) {
if (server.masterhost) {
sdsfree(server.masterhost);
server.masterhost = NULL;
if (server.master) freeClient(server.master);
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 = port;
if (server.master) freeClient(server.master);
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. */
}
}
}
}
}
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