/* Asynchronous replication implementation.
*
* Copyright (c) 2009-2012, Salvatore Sanfilippo <antirez at gmail dot com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of Redis nor the names of its contributors may be used
* to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include "redis.h"
#include <sys/time.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <sys/stat.h>
void replicationDiscardCachedMaster(void);
void replicationResurrectCachedMaster(int newfd);
/* ---------------------------------- MASTER -------------------------------- */
void createReplicationBacklog(void) {
redisAssert(server.repl_backlog == NULL);
server.repl_backlog = zmalloc(server.repl_backlog_size);
server.repl_backlog_histlen = 0;
server.repl_backlog_idx = 0;
/* When a new backlog buffer is created, we increment the replication
* offset by one to make sure we'll not be able to PSYNC with any
* previous slave. This is needed because we avoid incrementing the
* master_repl_offset if no backlog exists nor slaves are attached. */
server.master_repl_offset++;
/* We don't have any data inside our buffer, but virtually the first
* byte we have is the next byte that will be generated for the
* replication stream. */
server.repl_backlog_off = server.master_repl_offset+1;
}
/* This function is called when the user modifies the replication backlog
* size at runtime. It is up to the function to both update the
* server.repl_backlog_size and to resize the buffer and setup it so that
* it contains the same data as the previous one (possibly less data, but
* the most recent bytes, or the same data and more free space in case the
* buffer is enlarged). */
void resizeReplicationBacklog(long long newsize) {
if (newsize < REDIS_REPL_BACKLOG_MIN_SIZE)
newsize = REDIS_REPL_BACKLOG_MIN_SIZE;
if (server.repl_backlog_size == newsize) return;
server.repl_backlog_size = newsize;
if (server.repl_backlog != NULL) {
/* What we actually do is to flush the old buffer and realloc a new
* empty one. It will refill with new data incrementally.
* The reason is that copying a few gigabytes adds latency and even
* worse often we need to alloc additional space before freeing the
* old buffer. */
zfree(server.repl_backlog);
server.repl_backlog = zmalloc(server.repl_backlog_size);
server.repl_backlog_histlen = 0;
server.repl_backlog_idx = 0;
/* Next byte we have is... the next since the buffer is emtpy. */
server.repl_backlog_off = server.master_repl_offset+1;
}
}
void freeReplicationBacklog(void) {
redisAssert(listLength(server.slaves) == 0);
zfree(server.repl_backlog);
server.repl_backlog = NULL;
}
/* Add data to the replication backlog.
* This function also increments the global replication offset stored at
* server.master_repl_offset, because there is no case where we want to feed
* the backlog without incrementing the buffer. */
void feedReplicationBacklog(void *ptr, size_t len) {
unsigned char *p = ptr;
server.master_repl_offset += len;
/* This is a circular buffer, so write as much data we can at every
* iteration and rewind the "idx" index if we reach the limit. */
while(len) {
size_t thislen = server.repl_backlog_size - server.repl_backlog_idx;
if (thislen > len) thislen = len;
memcpy(server.repl_backlog+server.repl_backlog_idx,p,thislen);
server.repl_backlog_idx += thislen;
if (server.repl_backlog_idx == server.repl_backlog_size)
server.repl_backlog_idx = 0;
len -= thislen;
p += thislen;
server.repl_backlog_histlen += thislen;
}
if (server.repl_backlog_histlen > server.repl_backlog_size)
server.repl_backlog_histlen = server.repl_backlog_size;
/* Set the offset of the first byte we have in the backlog. */
server.repl_backlog_off = server.master_repl_offset -
server.repl_backlog_histlen + 1;
}
/* Wrapper for feedReplicationBacklog() that takes Redis string objects
* as input. */
void feedReplicationBacklogWithObject(robj *o) {
char llstr[REDIS_LONGSTR_SIZE];
void *p;
size_t len;
if (o->encoding == REDIS_ENCODING_INT) {
len = ll2string(llstr,sizeof(llstr),(long)o->ptr);
p = llstr;
} else {
len = sdslen(o->ptr);
p = o->ptr;
}
feedReplicationBacklog(p,len);
}
#define FEEDSLAVE_BUF_SIZE (1024*64)
void replicationFeedSlaves(list *slaves, int dictid, robj **argv, int argc) {
listNode *ln;
listIter li;
int j, i, len;
char buf[FEEDSLAVE_BUF_SIZE], *b = buf;
char llstr[REDIS_LONGSTR_SIZE];
int buf_left = FEEDSLAVE_BUF_SIZE;
robj *o;
/* If there aren't slaves, and there is no backlog buffer to populate,
* we can return ASAP. */
if (server.repl_backlog == NULL && listLength(slaves) == 0) return;
/* We can't have slaves attached and no backlog. */
redisAssert(!(listLength(slaves) != 0 && server.repl_backlog == NULL));
/* What we do here is to try to write as much data as possible in a static
* buffer "buf" that is used to create an object that is later sent to all
* the slaves. This way we do the decoding only one time for most commands
* not containing big payloads. */
/* Create the SELECT command into the static buffer if needed. */
if (server.slaveseldb != dictid) {
char *selectcmd;
size_t sclen;
if (dictid >= 0 && dictid < REDIS_SHARED_SELECT_CMDS) {
selectcmd = shared.select[dictid]->ptr;
sclen = sdslen(selectcmd);
memcpy(b,selectcmd,sclen);
b += sclen;
buf_left -= sclen;
} else {
int dictid_len;
dictid_len = ll2string(llstr,sizeof(llstr),dictid);
sclen = snprintf(b,buf_left,"*2\r\n$6\r\nSELECT\r\n$%d\r\n%s\r\n",
dictid_len, llstr);
b += sclen;
buf_left -= sclen;
}
}
server.slaveseldb = dictid;
/* Add the multi bulk reply size to the static buffer, that is, the number
* of arguments of the command to send to every slave. */
b[0] = '*';
len = ll2string(b+1,REDIS_LONGSTR_SIZE,argc);
b += len+1;
buf_left -= len;
b[0] = '\r';
b[1] = '\n';
b += 2;
buf_left -= 2;
/* Try to use the static buffer for as much arguments is possible. */
for (j = 0; j < argc; j++) {
int objlen;
char *objptr;
if (argv[j]->encoding != REDIS_ENCODING_RAW &&
argv[j]->encoding != REDIS_ENCODING_INT) {
redisPanic("Unexpected encoding");
}
if (argv[j]->encoding == REDIS_ENCODING_RAW) {
objlen = sdslen(argv[j]->ptr);
objptr = argv[j]->ptr;
} else {
objlen = ll2string(llstr,REDIS_LONGSTR_SIZE,(long)argv[j]->ptr);
objptr = llstr;
}
/* We need enough space for bulk reply encoding, newlines, and
* the data itself. */
if (buf_left < objlen+REDIS_LONGSTR_SIZE+32) break;
/* Write $...CRLF */
b[0] = '$';
len = ll2string(b+1,REDIS_LONGSTR_SIZE,objlen);
b += len+1;
buf_left -= len;
b[0] = '\r';
b[1] = '\n';
b += 2;
buf_left -= 2;
/* And data plus CRLF */
memcpy(b,objptr,objlen);
b += objlen;
buf_left -= objlen;
b[0] = '\r';
b[1] = '\n';
b += 2;
buf_left -= 2;
}
/* Create an object with the static buffer content. */
redisAssert(buf_left < FEEDSLAVE_BUF_SIZE);
o = createStringObject(buf,b-buf);
/* If we have a backlog, populate it with data and increment
* the global replication offset. */
if (server.repl_backlog) {
feedReplicationBacklogWithObject(o);
for (i = j; i < argc; i++) {
char aux[REDIS_LONGSTR_SIZE+3];
long objlen = stringObjectLen(argv[i]);
/* We need to feed the buffer with the object as a bulk reply
* not just as a plain string, so create the $..CRLF payload len
* ad add the final CRLF */
aux[0] = '$';
len = ll2string(aux+1,objlen,sizeof(aux)-1);
aux[len+1] = '\r';
aux[len+2] = '\n';
feedReplicationBacklog(aux,len+3);
feedReplicationBacklogWithObject(argv[j]);
feedReplicationBacklogWithObject(shared.crlf);
}
}
/* Write data to slaves. Here we do two things:
* 1) We write the "o" object that was created using the accumulated
* static buffer.
* 2) We write any additional argument of the command to replicate that
* was not written inside the static buffer for lack of space.
*/
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 initial SYNC completes),
* or are already in sync with the master. */
/* First, trasmit the object created from the static buffer. */
addReply(slave,o);
/* Finally any additional argument that was not stored inside the
* static buffer if any (from j to argc). */
for (i = j; i < argc; i++)
addReplyBulk(slave,argv[i]);
}
decrRefCount(o);
}
void replicationFeedMonitors(redisClient *c, list *monitors, int dictid, robj **argv, int argc) {
listNode *ln;
listIter li;
int j, port;
sds cmdrepr = sdsnew("+");
robj *cmdobj;
char ip[32];
struct timeval tv;
gettimeofday(&tv,NULL);
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 if (c->flags & REDIS_UNIX_SOCKET) {
cmdrepr = sdscatprintf(cmdrepr,"[%d unix:%s] ",dictid,server.unixsocket);
} 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) {
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);
}
/* Feed the slave 'c' with the replication backlog starting from the
* specified 'offset' up to the end of the backlog. */
long long addReplyReplicationBacklog(redisClient *c, long long offset) {
long long j, skip, len;
redisLog(REDIS_DEBUG, "[PSYNC] Slave request offset: %lld", offset);
if (server.repl_backlog_histlen == 0) {
redisLog(REDIS_DEBUG, "[PSYNC] Backlog history len is zero");
return 0;
}
redisLog(REDIS_DEBUG, "[PSYNC] Backlog size: %lld",
server.repl_backlog_size);
redisLog(REDIS_DEBUG, "[PSYNC] First byte: %lld",
server.repl_backlog_off);
redisLog(REDIS_DEBUG, "[PSYNC] History len: %lld",
server.repl_backlog_histlen);
redisLog(REDIS_DEBUG, "[PSYNC] Current index: %lld",
server.repl_backlog_idx);
/* Compute the amount of bytes we need to discard. */
skip = offset - server.repl_backlog_off;
redisLog(REDIS_DEBUG, "[PSYNC] Skipping: %lld", skip);
/* Point j to the oldest byte, that is actaully our
* server.repl_backlog_off byte. */
j = (server.repl_backlog_idx +
(server.repl_backlog_size-server.repl_backlog_histlen)) %
server.repl_backlog_size;
redisLog(REDIS_DEBUG, "[PSYNC] Index of first byte: %lld", j);
/* Discard the amount of data to seek to the specified 'offset'. */
j = (j + skip) % server.repl_backlog_size;
/* Feed slave with data. Since it is a circular buffer we have to
* split the reply in two parts if we are cross-boundary. */
len = server.repl_backlog_histlen - skip;
redisLog(REDIS_DEBUG, "[PSYNC] Reply total length: %lld", len);
while(len) {
long long thislen =
((server.repl_backlog_size - j) < len) ?
(server.repl_backlog_size - j) : len;
redisLog(REDIS_DEBUG, "[PSYNC] addReply() length: %lld", thislen);
addReplySds(c,sdsnewlen(server.repl_backlog + j, thislen));
len -= thislen;
j = 0;
}
return server.repl_backlog_histlen - skip;
}
/* This function handles the PSYNC command from the point of view of a
* master receiving a request for partial resynchronization.
*
* On success return REDIS_OK, otherwise REDIS_ERR is returned and we proceed
* with the usual full resync. */
int masterTryPartialResynchronization(redisClient *c) {
long long psync_offset, psync_len;
char *master_runid = c->argv[1]->ptr;
char buf[128];
int buflen;
/* Is the runid of this master the same advertised by the wannabe slave
* via PSYNC? If runid changed this master is a different instance and
* there is no way to continue. */
if (strcasecmp(master_runid, server.runid)) {
/* Run id "?" is used by slaves that want to force a full resync. */
if (master_runid[0] != '?') {
redisLog(REDIS_NOTICE,"Partial resynchronization not accepted: "
"Runid mismatch (Client asked for '%s', I'm '%s')",
master_runid, server.runid);
} else {
redisLog(REDIS_NOTICE,"Full resync requested by slave.");
}
goto need_full_resync;
}
/* We still have the data our slave is asking for? */
if (getLongLongFromObjectOrReply(c,c->argv[2],&psync_offset,NULL) !=
REDIS_OK) goto need_full_resync;
if (!server.repl_backlog ||
psync_offset < server.repl_backlog_off ||
psync_offset >= (server.repl_backlog_off + server.repl_backlog_size))
{
redisLog(REDIS_NOTICE,
"Unable to partial resync with the slave for lack of backlog (Slave request was: %lld).", psync_offset);
goto need_full_resync;
}
/* If we reached this point, we are able to perform a partial resync:
* 1) Set client state to make it a slave.
* 2) Inform the client we can continue with +CONTINUE
* 3) Send the backlog data (from the offset to the end) to the slave. */
c->flags |= REDIS_SLAVE;
c->replstate = REDIS_REPL_ONLINE;
listAddNodeTail(server.slaves,c);
/* We can't use the connection buffers since they are used to accumulate
* new commands at this stage. But we are sure the socket send buffer is
* emtpy so this write will never fail actually. */
buflen = snprintf(buf,sizeof(buf),"+CONTINUE\r\n");
if (write(c->fd,buf,buflen) != buflen) {
freeClientAsync(c);
return REDIS_OK;
}
psync_len = addReplyReplicationBacklog(c,psync_offset);
redisLog(REDIS_NOTICE,
"Partial resynchronization request accepted. Sending %lld bytes of backlog starting from offset %lld.", psync_len, psync_offset);
/* Note that we don't need to set the selected DB at server.slaveseldb
* to -1 to force the master to emit SELECT, since the slave already
* has this state from the previous connection with the master. */
return REDIS_OK; /* The caller can return, no full resync needed. */
need_full_resync:
/* We need a full resync for some reason... notify the client. */
psync_offset = server.master_repl_offset;
/* Add 1 to psync_offset if it the replication backlog does not exists
* as when it will be created later we'll increment the offset by one. */
if (server.repl_backlog == NULL) psync_offset++;
/* Again, we can't use the connection buffers (see above). */
buflen = snprintf(buf,sizeof(buf),"+FULLRESYNC %s %lld\r\n",
server.runid,psync_offset);
if (write(c->fd,buf,buflen) != buflen) {
freeClientAsync(c);
return REDIS_OK;
}
return REDIS_ERR;
}
/* SYNC ad PSYNC command implemenation. */
void syncCommand(redisClient *c) {
/* ignore SYNC if already 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 || c->bufpos != 0) {
addReplyError(c,"SYNC and PSYNC are invalid with pending output");
return;
}
redisLog(REDIS_NOTICE,"Slave asks for synchronization");
/* Try a partial resynchronization if this is a PSYNC command.
* If it fails, we continue with usual full resynchronization, however
* when this happens masterTryPartialResynchronization() already
* replied with:
*
* +FULLRESYNC <runid> <offset>
*
* So the slave knows the new runid and offset to try a PSYNC later
* if the connection with the master is lost. */
if (!strcasecmp(c->argv[0]->ptr,"psync")) {
if (masterTryPartialResynchronization(c) == REDIS_OK) {
server.stat_sync_partial_ok++;
return; /* No full resync needed, return. */
} else {
char *master_runid = c->argv[1]->ptr;
/* Increment stats for failed PSYNCs, but only if the
* runid is not "?", as this is used by slaves to force a full
* resync on purpose when they are not albe to partially
* resync. */
if (master_runid[0] != '?') server.stat_sync_partial_err++;
}
}
/* Full resynchronization. */
server.stat_sync_full++;
/* 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;
}
if (server.repl_disable_tcp_nodelay)
anetDisableTcpNoDelay(NULL, c->fd); /* Non critical if it fails. */
c->repldbfd = -1;
c->flags |= REDIS_SLAVE;
server.slaveseldb = -1; /* Force to re-emit the SELECT command. */
listAddNodeTail(server.slaves,c);
if (listLength(server.slaves) == 1 && server.repl_backlog == NULL)
createReplicationBacklog();
return;
}
/* REPLCONF <option> <value> <option> <value> ...
* This command is used by a slave in order to configure the replication
* process before starting it with the SYNC command.
*
* Currently the only use of this command is to communicate to the master
* what is the listening port of the Slave redis instance, so that the
* master can accurately list slaves and their listening ports in
* the INFO output.
*
* In the future the same command can be used in order to configure
* the replication to initiate an incremental replication instead of a
* full resync. */
void replconfCommand(redisClient *c) {
int j;
if ((c->argc % 2) == 0) {
/* Number of arguments must be odd to make sure that every
* option has a corresponding value. */
addReply(c,shared.syntaxerr);
return;
}
/* Process every option-value pair. */
for (j = 1; j < c->argc; j+=2) {
if (!strcasecmp(c->argv[j]->ptr,"listening-port")) {
long port;
if ((getLongFromObjectOrReply(c,c->argv[j+1],
&port,NULL) != REDIS_OK))
return;
c->slave_listening_port = port;
} else if (!strcasecmp(c->argv[j]->ptr,"ack")) {
/* REPLCONF ACK is used by slave to inform the master the amount
* of replication stream that it processed so far. It is an
* internal only command that normal clients should never use. */
long long offset;
if (!(c->flags & REDIS_SLAVE)) return;
if ((getLongLongFromObject(c->argv[j+1], &offset) != REDIS_OK))
return;
if (offset > c->repl_ack_off)
c->repl_ack_off = offset;
c->repl_ack_time = server.unixtime;
/* Note: this command does not reply anything! */
return;
} else {
addReplyErrorFormat(c,"Unrecognized REPLCONF option: %s",
(char*)c->argv[j]->ptr);
return;
}
}
addReply(c,shared.ok);
}
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 practice 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;
}
redisLog(REDIS_NOTICE,"Synchronization with slave succeeded");
}
}
/* This function is called at the end of every background 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 */
#define REPL_MAX_WRITTEN_BEFORE_FSYNC (1024*1024*8) /* 8 MB */
void readSyncBulkPayload(aeEventLoop *el, int fd, void *privdata, int mask) {
char buf[4096];
ssize_t nread, readlen;
off_t left;
REDIS_NOTUSED(el);
REDIS_NOTUSED(privdata);
REDIS_NOTUSED(mask);
/* If repl_transfer_size == -1 we still have to read the bulk length
* from the master reply. */
if (server.repl_transfer_size == -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 '$' (we received '%s'), are you sure the host and port are right?", buf);
goto error;
}
server.repl_transfer_size = strtol(buf+1,NULL,10);
redisLog(REDIS_NOTICE,
"MASTER <-> SLAVE sync: receiving %lld bytes from master",
(long long) server.repl_transfer_size);
return;
}
/* Read bulk data */
left = server.repl_transfer_size - server.repl_transfer_read;
readlen = (left < (signed)sizeof(buf)) ? 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_read += nread;
/* Sync data on disk from time to time, otherwise at the end of the transfer
* we may suffer a big delay as the memory buffers are copied into the
* actual disk. */
if (server.repl_transfer_read >=
server.repl_transfer_last_fsync_off + REPL_MAX_WRITTEN_BEFORE_FSYNC)
{
off_t sync_size = server.repl_transfer_read -
server.repl_transfer_last_fsync_off;
rdb_fsync_range(server.repl_transfer_fd,
server.repl_transfer_last_fsync_off, sync_size);
server.repl_transfer_last_fsync_off += sync_size;
}
/* Check if the transfer is now complete */
if (server.repl_transfer_read == server.repl_transfer_size) {
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");
signalFlushedDb(-1);
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;
server.master->reploff = server.repl_master_initial_offset;
memcpy(server.master->replrunid, server.repl_master_runid,
sizeof(server.repl_master_runid));
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 synchronization! 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;
}
/* Send a synchronous command to the master. Used to send AUTH and
* REPLCONF commands before starting the replication with SYNC.
*
* The command returns an sds string representing the result of the
* operation. On error the first byte is a "-".
*/
char *sendSynchronousCommand(int fd, ...) {
va_list ap;
sds cmd = sdsempty();
char *arg, buf[256];
/* Create the command to send to the master, we use simple inline
* protocol for simplicity as currently we only send simple strings. */
va_start(ap,fd);
while(1) {
arg = va_arg(ap, char*);
if (arg == NULL) break;
if (sdslen(cmd) != 0) cmd = sdscatlen(cmd," ",1);
cmd = sdscat(cmd,arg);
}
cmd = sdscatlen(cmd,"\r\n",2);
/* Transfer command to the server. */
if (syncWrite(fd,cmd,sdslen(cmd),server.repl_syncio_timeout*1000) == -1) {
sdsfree(cmd);
return sdscatprintf(sdsempty(),"-Writing to master: %s",
strerror(errno));
}
sdsfree(cmd);
/* Read the reply from the server. */
if (syncReadLine(fd,buf,sizeof(buf),server.repl_syncio_timeout*1000) == -1)
{
return sdscatprintf(sdsempty(),"-Reading from master: %s",
strerror(errno));
}
return sdsnew(buf);
}
/* Try a partial resynchronization with the master if we are about to reconnect.
* If there is no cached master structure, at least try to issue a
* "PSYNC ? -1" command in order to trigger a full resync using the PSYNC
* command in order to obtain the master run id and the master replication
* global offset.
*
* This function is designed to be called from syncWithMaster(), so the
* following assumptions are made:
*
* 1) We pass the function an already connected socket "fd".
* 2) This function does not close the file descriptor "fd". However in case
* of successful partial resynchronization, the function will reuse
* 'fd' as file descriptor of the server.master client structure.
*
* The function returns:
*
* PSYNC_CONTINUE: If the PSYNC command succeded and we can continue.
* PSYNC_FULLRESYNC: If PSYNC is supported but a full resync is needed.
* In this case the master run_id and global replication
* offset is saved.
* PSYNC_NOT_SUPPORTED: If the server does not understand PSYNC at all and
* the caller should fall back to SYNC.
*/
#define PSYNC_CONTINUE 0
#define PSYNC_FULLRESYNC 1
#define PSYNC_NOT_SUPPORTED 2
int slaveTryPartialResynchronization(int fd) {
char *psync_runid;
char psync_offset[32];
sds reply;
/* Initially set repl_master_initial_offset to -1 to mark the current
* master run_id and offset as not valid. Later if we'll be able to do
* a FULL resync using the PSYNC command we'll set the offset at the
* right value, so that this information will be propagated to the
* client structure representing the master into server.master. */
server.repl_master_initial_offset = -1;
if (server.cached_master) {
psync_runid = server.cached_master->replrunid;
snprintf(psync_offset,sizeof(psync_offset),"%lld", server.cached_master->reploff+1);
redisLog(REDIS_NOTICE,"Trying a partial resynchronization (request %s:%s).", psync_runid, psync_offset);
} else {
redisLog(REDIS_NOTICE,"Partial resynchronization not possible (no cached master)");
psync_runid = "?";
memcpy(psync_offset,"-1",3);
}
/* Issue the PSYNC command */
reply = sendSynchronousCommand(fd,"PSYNC",psync_runid,psync_offset,NULL);
if (!strncmp(reply,"+FULLRESYNC",11)) {
char *runid = NULL, *offset = NULL;
/* FULL RESYNC, parse the reply in order to extract the run id
* and the replication offset. */
runid = strchr(reply,' ');
if (runid) {
runid++;
offset = strchr(runid,' ');
if (offset) offset++;
}
if (!runid || !offset || (offset-runid-1) != REDIS_RUN_ID_SIZE) {
redisLog(REDIS_WARNING,
"Master replied with wrong +FULLRESYNC syntax.");
/* This is an unexpected condition, actually the +FULLRESYNC
* reply means that the master supports PSYNC, but the reply
* format seems wrong. To stay safe we blank the master
* runid to make sure next PSYNCs will fail. */
memset(server.repl_master_runid,0,REDIS_RUN_ID_SIZE+1);
} else {
memcpy(server.repl_master_runid, runid, offset-runid-1);
server.repl_master_runid[REDIS_RUN_ID_SIZE] = '\0';
server.repl_master_initial_offset = strtoll(offset,NULL,10);
redisLog(REDIS_NOTICE,"Full resync from master: %s:%lld",
server.repl_master_runid,
server.repl_master_initial_offset);
}
/* We are going to full resync, discard the cached master structure. */
replicationDiscardCachedMaster();
sdsfree(reply);
return PSYNC_FULLRESYNC;
}
if (!strncmp(reply,"+CONTINUE",9)) {
/* Partial resync was accepted, set the replication state accordingly */
redisLog(REDIS_NOTICE,
"Successful partial resynchronization with master.");
sdsfree(reply);
replicationResurrectCachedMaster(fd);
return PSYNC_CONTINUE;
}
/* If we reach this point we receied either an error since the master does
* not understand PSYNC, or an unexpected reply from the master.
* Reply with PSYNC_NOT_SUPPORTED in both cases. */
if (strncmp(reply,"-ERR",4)) {
/* If it's not an error, log the unexpected event. */
redisLog(REDIS_WARNING,
"Unexpected reply to PSYNC from master: %s", reply);
} else {
redisLog(REDIS_NOTICE,
"Master does not support PSYNC or is in "
"error state (reply: %s)", reply);
}
sdsfree(reply);
replicationDiscardCachedMaster();
return PSYNC_NOT_SUPPORTED;
}
void syncWithMaster(aeEventLoop *el, int fd, void *privdata, int mask) {
char tmpfile[256], *err;
int dfd, maxtries = 5;
int sockerr = 0, psync_result;
socklen_t errlen = sizeof(sockerr);
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;
}
/* Check for errors in the socket. */
if (getsockopt(fd, SOL_SOCKET, SO_ERROR, &sockerr, &errlen) == -1)
sockerr = errno;
if (sockerr) {
aeDeleteFileEvent(server.el,fd,AE_READABLE|AE_WRITABLE);
redisLog(REDIS_WARNING,"Error condition on socket for SYNC: %s",
strerror(sockerr));
goto error;
}
/* If we were connecting, it's time to send a non blocking PING, we want to
* make sure the master is able to reply before going into the actual
* replication process where we have long timeouts in the order of
* seconds (in the meantime the slave would block). */
if (server.repl_state == REDIS_REPL_CONNECTING) {
redisLog(REDIS_NOTICE,"Non blocking connect for SYNC fired the event.");
/* Delete the writable event so that the readable event remains
* registered and we can wait for the PONG reply. */
aeDeleteFileEvent(server.el,fd,AE_WRITABLE);
server.repl_state = REDIS_REPL_RECEIVE_PONG;
/* Send the PING, don't check for errors at all, we have the timeout
* that will take care about this. */
syncWrite(fd,"PING\r\n",6,100);
return;
}
/* Receive the PONG command. */
if (server.repl_state == REDIS_REPL_RECEIVE_PONG) {
char buf[1024];
/* Delete the readable event, we no longer need it now that there is
* the PING reply to read. */
aeDeleteFileEvent(server.el,fd,AE_READABLE);
/* Read the reply with explicit timeout. */
buf[0] = '\0';
if (syncReadLine(fd,buf,sizeof(buf),
server.repl_syncio_timeout*1000) == -1)
{
redisLog(REDIS_WARNING,
"I/O error reading PING reply from master: %s",
strerror(errno));
goto error;
}
/* We accept only two replies as valid, a positive +PONG reply
* (we just check for "+") or an authentication error.
* Note that older versions of Redis replied with "operation not
* permitted" instead of using a proper error code, so we test
* both. */
if (buf[0] != '+' &&
strncmp(buf,"-NOAUTH",7) != 0 &&
strncmp(buf,"-ERR operation not permitted",28) != 0)
{
redisLog(REDIS_WARNING,"Error reply to PING from master: '%s'",buf);
goto error;
} else {
redisLog(REDIS_NOTICE,
"Master replied to PING, replication can continue...");
}
}
/* AUTH with the master if required. */
if(server.masterauth) {
err = sendSynchronousCommand(fd,"AUTH",server.masterauth,NULL);
if (err[0] == '-') {
redisLog(REDIS_WARNING,"Unable to AUTH to MASTER: %s",err);
sdsfree(err);
goto error;
}
sdsfree(err);
}
/* Set the slave port, so that Master's INFO command can list the
* slave listening port correctly. */
{
sds port = sdsfromlonglong(server.port);
err = sendSynchronousCommand(fd,"REPLCONF","listening-port",port,
NULL);
sdsfree(port);
/* Ignore the error if any, not all the Redis versions support
* REPLCONF listening-port. */
if (err[0] == '-') {
redisLog(REDIS_NOTICE,"(Non critical) Master does not understand REPLCONF listening-port: %s", err);
}
sdsfree(err);
}
/* Try a partial resynchonization. If we don't have a cached master
* slaveTryPartialResynchronization() will at least try to use PSYNC
* to start a full resynchronization so that we get the master run id
* and the global offset, to try a partial resync at the next
* reconnection attempt. */
psync_result = slaveTryPartialResynchronization(fd);
if (psync_result == PSYNC_CONTINUE) {
redisLog(REDIS_NOTICE, "MASTER <-> SLAVE sync: Master accepted a Partial Resynchronization.");
return;
}
/* Fall back to SYNC if needed. Otherwise psync_result == PSYNC_FULLRESYNC
* and the server.repl_master_runid and repl_master_initial_offset are
* already populated. */
if (psync_result == PSYNC_NOT_SUPPORTED) {
redisLog(REDIS_NOTICE,"Retrying with SYNC...");
if (syncWrite(fd,"SYNC\r\n",6,server.repl_syncio_timeout*1000) == -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)server.unixtime,(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: %s (fd=%d)",
strerror(errno),fd);
goto error;
}
server.repl_state = REDIS_REPL_TRANSFER;
server.repl_transfer_size = -1;
server.repl_transfer_read = 0;
server.repl_transfer_last_fsync_off = 0;
server.repl_transfer_fd = dfd;
server.repl_transfer_lastio = server.unixtime;
server.repl_transfer_tmpfile = zstrdup(tmpfile);
return;
error:
close(fd);
server.repl_transfer_s = -1;
server.repl_state = REDIS_REPL_CONNECT;
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 = 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 ||
server.repl_state == REDIS_REPL_RECEIVE_PONG);
aeDeleteFileEvent(server.el,fd,AE_READABLE|AE_WRITABLE);
close(fd);
server.repl_transfer_s = -1;
server.repl_state = REDIS_REPL_CONNECT;
}
/* This function aborts a non blocking replication attempt if there is one
* in progress, by canceling the non-blocking connect attempt or
* the initial bulk transfer.
*
* If there was a replication handshake in progress 1 is returned and
* the replication state (server.repl_state) set to REDIS_REPL_CONNECT.
*
* Otherwise zero is returned and no operation is perforemd at all. */
int cancelReplicationHandshake(void) {
if (server.repl_state == REDIS_REPL_TRANSFER) {
replicationAbortSyncTransfer();
} else if (server.repl_state == REDIS_REPL_CONNECTING ||
server.repl_state == REDIS_REPL_RECEIVE_PONG)
{
undoConnectWithMaster();
} else {
return 0;
}
return 1;
}
/* Set replication to the specified master address and port. */
void replicationSetMaster(char *ip, int port) {
sdsfree(server.masterhost);
server.masterhost = sdsnew(ip);
server.masterport = port;
if (server.master) freeClient(server.master);
disconnectSlaves(); /* Force our slaves to resync with us as well. */
replicationDiscardCachedMaster(); /* Don't try a PSYNC. */
freeReplicationBacklog(); /* Don't allow our chained slaves to PSYNC. */
cancelReplicationHandshake();
server.repl_state = REDIS_REPL_CONNECT;
}
/* Cancel replication, setting the instance as a master itself. */
void replicationUnsetMaster(void) {
if (server.masterhost == NULL) return; /* Nothing to do. */
sdsfree(server.masterhost);
server.masterhost = NULL;
if (server.master) freeClient(server.master);
replicationDiscardCachedMaster();
cancelReplicationHandshake();
server.repl_state = REDIS_REPL_NONE;
}
void slaveofCommand(redisClient *c) {
/* SLAVEOF is not allowed in cluster mode as replication is automatically
* configured using the current address of the master node. */
if (server.cluster_enabled) {
addReplyError(c,"SLAVEOF not allowed in cluster mode.");
return;
}
/* The special host/port combination "NO" "ONE" turns the instance
* into a master. Otherwise the new master address is set. */
if (!strcasecmp(c->argv[1]->ptr,"no") &&
!strcasecmp(c->argv[2]->ptr,"one")) {
if (server.masterhost) {
replicationUnsetMaster();
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. */
replicationSetMaster(c->argv[1]->ptr, port);
redisLog(REDIS_NOTICE,"SLAVE OF %s:%d enabled (user request)",
server.masterhost, server.masterport);
}
addReply(c,shared.ok);
}
/* Send a REPLCONF ACK command to the master to inform it about the current
* processed offset. If we are not connected with a master, the command has
* no effects. */
void replicationSendAck(void) {
redisClient *c = server.master;
if (c != NULL) {
c->flags |= REDIS_MASTER_FORCE_REPLY;
addReplyMultiBulkLen(c,3);
addReplyBulkCString(c,"REPLCONF");
addReplyBulkCString(c,"ACK");
addReplyBulkLongLong(c,c->reploff);
c->flags &= ~REDIS_MASTER_FORCE_REPLY;
}
}
/* ---------------------- MASTER CACHING FOR PSYNC -------------------------- */
/* In order to implement partial synchronization we need to be able to cache
* our master's client structure after a transient disconnection.
* It is cached into server.cached_master and flushed away using the following
* functions. */
/* This function is called by freeClient() in order to cache the master
* client structure instead of destryoing it. freeClient() will return
* ASAP after this function returns, so every action needed to avoid problems
* with a client that is really "suspended" has to be done by this function.
*
* The other functions that will deal with the cached master are:
*
* replicationDiscardCachedMaster() that will make sure to kill the client
* as for some reason we don't want to use it in the future.
*
* replicationResurrectCachedMaster() that is used after a successful PSYNC
* handshake in order to reactivate the cached master.
*/
void replicationCacheMaster(redisClient *c) {
listNode *ln;
redisAssert(server.master != NULL && server.cached_master == NULL);
redisLog(REDIS_NOTICE,"Caching the disconnected master state.");
/* Remove from the list of clients, we don't want this client to be
* listed by CLIENT LIST or processed in any way by batch operations. */
ln = listSearchKey(server.clients,c);
redisAssert(ln != NULL);
listDelNode(server.clients,ln);
/* Save the master. Server.master will be set to null later by
* replicationHandleMasterDisconnection(). */
server.cached_master = server.master;
/* Remove the event handlers and close the socket. We'll later reuse
* the socket of the new connection with the master during PSYNC. */
aeDeleteFileEvent(server.el,c->fd,AE_READABLE);
aeDeleteFileEvent(server.el,c->fd,AE_WRITABLE);
close(c->fd);
/* Set fd to -1 so that we can safely call freeClient(c) later. */
c->fd = -1;
/* Caching the master happens instead of the actual freeClient() call,
* so make sure to adjust the replication state. This function will
* also set server.master to NULL. */
replicationHandleMasterDisconnection();
}
/* Free a cached master, called when there are no longer the conditions for
* a partial resync on reconnection. */
void replicationDiscardCachedMaster(void) {
if (server.cached_master == NULL) return;
redisLog(REDIS_NOTICE,"Discarding previously cached master state.");
server.cached_master->flags &= ~REDIS_MASTER;
freeClient(server.cached_master);
server.cached_master = NULL;
}
/* Turn the cached master into the current master, using the file descriptor
* passed as argument as the socket for the new master.
*
* This funciton is called when successfully setup a partial resynchronization
* so the stream of data that we'll receive will start from were this
* master left. */
void replicationResurrectCachedMaster(int newfd) {
server.master = server.cached_master;
server.cached_master = NULL;
server.master->fd = newfd;
server.master->flags &= ~(REDIS_CLOSE_AFTER_REPLY|REDIS_CLOSE_ASAP);
server.master->authenticated = 1;
server.master->lastinteraction = server.unixtime;
server.repl_state = REDIS_REPL_CONNECTED;
/* Re-add to the list of clients. */
listAddNodeTail(server.clients,server.master);
if (aeCreateFileEvent(server.el, newfd, AE_READABLE,
readQueryFromClient, server.master)) {
redisLog(REDIS_WARNING,"Error resurrecting the cached master, impossible to add the readable handler: %s", strerror(errno));
freeClientAsync(server.master); /* Close ASAP. */
}
}
/* --------------------------- REPLICATION CRON ---------------------------- */
/* Replication cron funciton, called 1 time per second. */
void replicationCron(void) {
/* Non blocking connection timeout? */
if (server.masterhost &&
(server.repl_state == REDIS_REPL_CONNECTING ||
server.repl_state == REDIS_REPL_RECEIVE_PONG) &&
(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... If the problem persists try to set the 'repl-timeout' parameter in redis.conf to a larger value.");
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 * server.hz))) {
listIter li;
listNode *ln;
robj *ping_argv[1];
/* First, send PING */
ping_argv[0] = createStringObject("PING",4);
replicationFeedSlaves(server.slaves, server.slaveseldb, ping_argv, 1);
decrRefCount(ping_argv[0]);
/* Second, send a newline to all the slaves in pre-synchronization
* stage, that is, slaves waiting for the master to create the RDB file.
* The newline will be ignored by the slave but will refresh the
* last-io timer preventing a timeout. */
listRewind(server.slaves,&li);
while((ln = listNext(&li))) {
redisClient *slave = ln->value;
if (slave->replstate == REDIS_REPL_WAIT_BGSAVE_START ||
slave->replstate == REDIS_REPL_WAIT_BGSAVE_END) {
if (write(slave->fd, "\n", 1) == -1) {
/* Don't worry, it's just a ping. */
}
}
}
}
/* If we have no attached slaves and there is a replication backlog
* using memory, free it after some (configured) time. */
if (listLength(server.slaves) == 0 && server.repl_backlog_time_limit &&
server.repl_backlog)
{
time_t idle = server.unixtime - server.repl_no_slaves_since;
if (idle > server.repl_backlog_time_limit) {
freeReplicationBacklog();
redisLog(REDIS_NOTICE,
"Replication backlog freed after %d seconds "
"without connected slaves.",
(int) server.repl_backlog_time_limit);
}
}
}