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Diskless replication: RDB -> slaves transfer draft implementation.

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This commit is contained in:
antirez
2014-10-14 10:11:26 +02:00
parent 850ea57c37
commit 75f0cd6520
5 changed files with 200 additions and 28 deletions
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139
src/rdb.c
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@ -689,6 +689,32 @@ werr:
return REDIS_ERR;
}
/* This is just a wrapper to rdbSaveRio() that additionally adds a prefix
* and a suffix to the generated RDB dump. The prefix is:
*
* $EOF:<40 bytes unguessable hex string>\r\n
*
* While the suffix is the 40 bytes hex string we announced in the prefix.
* This way processes receiving the payload can understand when it ends
* without doing any processing of the content. */
int rdbSaveRioWithEOFMark(rio *rdb, int *error) {
char eofmark[REDIS_EOF_MARK_SIZE];
getRandomHexChars(eofmark,REDIS_EOF_MARK_SIZE);
if (error) *error = 0;
if (rioWrite(rdb,"$EOF:",5) == 0) goto werr;
if (rioWrite(rdb,eofmark,REDIS_EOF_MARK_SIZE) == 0) goto werr;
if (rioWrite(rdb,"\r\n",2) == 0) goto werr;
if (rdbSaveRio(rdb,error) == REDIS_ERR) goto werr;
if (rioWrite(rdb,eofmark,REDIS_EOF_MARK_SIZE) == 0) goto werr;
return REDIS_OK;
werr: /* Write error. */
/* Set 'error' only if not already set by rdbSaveRio() call. */
if (error && *error == 0) *error = errno;
return REDIS_ERR;
}
/* Save the DB on disk. Return REDIS_ERR on error, REDIS_OK on success. */
int rdbSave(char *filename) {
char tmpfile[256];
@ -1211,8 +1237,9 @@ eoferr: /* unexpected end of file is handled here with a fatal exit */
return REDIS_ERR; /* Just to avoid warning */
}
/* A background saving child (BGSAVE) terminated its work. Handle this. */
void backgroundSaveDoneHandler(int exitcode, int bysignal) {
/* A background saving child (BGSAVE) terminated its work. Handle this.
* This function covers the case of actual BGSAVEs. */
void backgroundSaveDoneHandlerDisk(int exitcode, int bysignal) {
if (!bysignal && exitcode == 0) {
redisLog(REDIS_NOTICE,
"Background saving terminated with success");
@ -1242,7 +1269,113 @@ void backgroundSaveDoneHandler(int exitcode, int bysignal) {
server.rdb_save_time_start = -1;
/* Possibly there are slaves waiting for a BGSAVE in order to be served
* (the first stage of SYNC is a bulk transfer of dump.rdb) */
updateSlavesWaitingBgsave((!bysignal && exitcode == 0) ? REDIS_OK : REDIS_ERR);
updateSlavesWaitingBgsave((!bysignal && exitcode == 0) ? REDIS_OK : REDIS_ERR, REDIS_RDB_CHILD_TYPE_DISK);
}
/* A background saving child (BGSAVE) terminated its work. Handle this.
* This function covers the case of RDB -> Salves socket transfers for
* diskless replication. */
void backgroundSaveDoneHandlerSocket(int exitcode, int bysignal) {
if (!bysignal && exitcode == 0) {
redisLog(REDIS_NOTICE,
"Background RDB transfer terminated with success");
} else if (!bysignal && exitcode != 0) {
redisLog(REDIS_WARNING, "Background transfer error");
} else {
redisLog(REDIS_WARNING,
"Background transfer terminated by signal %d", bysignal);
}
server.rdb_child_pid = -1;
server.rdb_child_type = REDIS_RDB_CHILD_TYPE_NONE;
server.rdb_save_time_start = -1;
/* Possibly there are slaves waiting for a BGSAVE in order to be served
* (the first stage of SYNC is a bulk transfer of dump.rdb) */
updateSlavesWaitingBgsave((!bysignal && exitcode == 0) ? REDIS_OK : REDIS_ERR, REDIS_RDB_CHILD_TYPE_SOCKET);
}
/* When a background RDB saving/transfer terminates, call the right handler. */
void backgroundSaveDoneHandler(int exitcode, int bysignal) {
switch(server.rdb_child_type) {
case REDIS_RDB_CHILD_TYPE_DISK:
backgroundSaveDoneHandlerDisk(exitcode,bysignal);
break;
case REDIS_RDB_CHILD_TYPE_SOCKET:
backgroundSaveDoneHandlerSocket(exitcode,bysignal);
break;
default:
redisPanic("Unknown RDB child type.");
break;
}
}
/* Spawn an RDB child that writes the RDB to the sockets of the slaves
* that are currently in REDIS_REPL_WAIT_BGSAVE_START state. */
int rdbSaveToSlavesSockets(void) {
int *fds;
int numfds;
listNode *ln;
listIter li;
pid_t childpid;
long long start;
if (server.rdb_child_pid != -1) return REDIS_ERR;
fds = zmalloc(sizeof(int)*listLength(server.slaves));
numfds = 0;
listRewind(server.slaves,&li);
while((ln = listNext(&li))) {
redisClient *slave = ln->value;
if (slave->replstate == REDIS_REPL_WAIT_BGSAVE_START) {
fds[numfds++] = slave->fd;
slave->replstate = REDIS_REPL_WAIT_BGSAVE_END;
}
}
/* Fork ... */
start = ustime();
if ((childpid = fork()) == 0) {
/* Child */
int retval;
rio slave_sockets;
rioInitWithFdset(&slave_sockets,fds,numfds);
zfree(fds);
closeListeningSockets(0);
redisSetProcTitle("redis-rdb-to-slaves");
retval = rdbSaveRioWithEOFMark(&slave_sockets,NULL);
if (retval == REDIS_OK) {
size_t private_dirty = zmalloc_get_private_dirty();
if (private_dirty) {
redisLog(REDIS_NOTICE,
"RDB: %zu MB of memory used by copy-on-write",
private_dirty/(1024*1024));
}
}
exitFromChild((retval == REDIS_OK) ? 0 : 1);
} else {
/* Parent */
server.stat_fork_time = ustime()-start;
server.stat_fork_rate = (double) zmalloc_used_memory() * 1000000 / server.stat_fork_time / (1024*1024*1024); /* GB per second. */
latencyAddSampleIfNeeded("fork",server.stat_fork_time/1000);
if (childpid == -1) {
redisLog(REDIS_WARNING,"Can't save in background: fork: %s",
strerror(errno));
return REDIS_ERR;
}
redisLog(REDIS_NOTICE,"Background RDB transfer started by pid %d",childpid);
server.rdb_save_time_start = time(NULL);
server.rdb_child_pid = childpid;
server.rdb_child_type = REDIS_RDB_CHILD_TYPE_SOCKET;
updateDictResizePolicy();
zfree(fds);
return REDIS_OK;
}
return REDIS_OK; /* unreached */
}
void saveCommand(redisClient *c) {