#include "redis.h"
+#include "bio.h"
#include <signal.h>
#include <fcntl.h>
void aofUpdateCurrentSize(void);
+void aof_background_fsync(int fd) {
+ bioCreateBackgroundJob(REDIS_BIO_AOF_FSYNC,(void*)(long)fd,NULL,NULL);
+}
+
/* Called when the user switches from "appendonly yes" to "appendonly no"
* at runtime using the CONFIG command. */
void stopAppendOnly(void) {
- flushAppendOnlyFile();
+ flushAppendOnlyFile(1);
aof_fsync(server.appendfd);
close(server.appendfd);
* and the only way the client socket can get a write is entering when the
* the event loop, we accumulate all the AOF writes in a memory
* buffer and write it on disk using this function just before entering
- * the event loop again. */
-void flushAppendOnlyFile(void) {
- time_t now;
+ * the event loop again.
+ *
+ * About the 'force' argument:
+ *
+ * When the fsync policy is set to 'everysec' we may delay the flush if there
+ * is still an fsync() going on in the background thread, since for instance
+ * on Linux write(2) will be blocked by the background fsync anyway.
+ * When this happens we remember that there is some aof buffer to be
+ * flushed ASAP, and will try to do that in the serverCron() function.
+ *
+ * However if force is set to 1 we'll write regardless of the background
+ * fsync. */
+void flushAppendOnlyFile(int force) {
ssize_t nwritten;
+ int sync_in_progress = 0;
if (sdslen(server.aofbuf) == 0) return;
+ if (server.appendfsync == APPENDFSYNC_EVERYSEC)
+ sync_in_progress = bioPendingJobsOfType(REDIS_BIO_AOF_FSYNC) != 0;
+
+ if (server.appendfsync == APPENDFSYNC_EVERYSEC && !force) {
+ /* With this append fsync policy we do background fsyncing.
+ * If the fsync is still in progress we can try to delay
+ * the write for a couple of seconds. */
+ if (sync_in_progress) {
+ if (server.aof_flush_postponed_start == 0) {
+ /* No previous write postponinig, remember that we are
+ * postponing the flush and return. */
+ server.aof_flush_postponed_start = server.unixtime;
+ return;
+ } else if (server.unixtime - server.aof_flush_postponed_start < 2) {
+ /* We were already waiting for fsync to finish, but for less
+ * than two seconds this is still ok. Postpone again. */
+ return;
+ }
+ /* Otherwise fall trough, and go write since we can't wait
+ * over two seconds. */
+ redisLog(REDIS_NOTICE,"Asynchronous AOF fsync is taking too long (disk is busy?). Writing the AOF buffer without waiting for fsync to complete, this may slow down Redis.");
+ }
+ }
+ /* If you are following this code path, then we are going to write so
+ * set reset the postponed flush sentinel to zero. */
+ server.aof_flush_postponed_start = 0;
+
/* We want to perform a single write. This should be guaranteed atomic
* at least if the filesystem we are writing is a real physical one.
* While this will save us against the server being killed I don't think
* there is much to do about the whole server stopping for power problems
* or alike */
- nwritten = write(server.appendfd,server.aofbuf,sdslen(server.aofbuf));
- if (nwritten != (signed)sdslen(server.aofbuf)) {
+ nwritten = write(server.appendfd,server.aofbuf,sdslen(server.aofbuf));
+ if (nwritten != (signed)sdslen(server.aofbuf)) {
/* Ooops, we are in troubles. The best thing to do for now is
* aborting instead of giving the illusion that everything is
* working as expected. */
- if (nwritten == -1) {
+ if (nwritten == -1) {
redisLog(REDIS_WARNING,"Exiting on error writing to the append-only file: %s",strerror(errno));
- } else {
+ } else {
redisLog(REDIS_WARNING,"Exiting on short write while writing to the append-only file: %s",strerror(errno));
- }
- exit(1);
+ }
+ exit(1);
}
- sdsfree(server.aofbuf);
- server.aofbuf = sdsempty();
server.appendonly_current_size += nwritten;
- /* Don't Fsync if no-appendfsync-on-rewrite is set to yes and we have
- * childs performing heavy I/O on disk. */
+ /* Re-use AOF buffer when it is small enough. The maximum comes from the
+ * arena size of 4k minus some overhead (but is otherwise arbitrary). */
+ if ((sdslen(server.aofbuf)+sdsavail(server.aofbuf)) < 4000) {
+ sdsclear(server.aofbuf);
+ } else {
+ sdsfree(server.aofbuf);
+ server.aofbuf = sdsempty();
+ }
+
+ /* Don't fsync if no-appendfsync-on-rewrite is set to yes and there are
+ * children doing I/O in the background. */
if (server.no_appendfsync_on_rewrite &&
(server.bgrewritechildpid != -1 || server.bgsavechildpid != -1))
return;
- /* Fsync if needed */
- now = time(NULL);
- if (server.appendfsync == APPENDFSYNC_ALWAYS ||
- (server.appendfsync == APPENDFSYNC_EVERYSEC &&
- now-server.lastfsync > 1))
- {
+
+ /* Perform the fsync if needed. */
+ if (server.appendfsync == APPENDFSYNC_ALWAYS) {
/* aof_fsync is defined as fdatasync() for Linux in order to avoid
* flushing metadata. */
aof_fsync(server.appendfd); /* Let's try to get this data on the disk */
- server.lastfsync = now;
+ server.lastfsync = server.unixtime;
+ } else if ((server.appendfsync == APPENDFSYNC_EVERYSEC &&
+ server.unixtime > server.lastfsync)) {
+ if (!sync_in_progress) aof_background_fsync(server.appendfd);
+ server.lastfsync = server.unixtime;
}
}
-sds catAppendOnlyGenericCommand(sds buf, int argc, robj **argv) {
- int j;
- buf = sdscatprintf(buf,"*%d\r\n",argc);
+sds catAppendOnlyGenericCommand(sds dst, int argc, robj **argv) {
+ char buf[32];
+ int len, j;
+ robj *o;
+
+ buf[0] = '*';
+ len = 1+ll2string(buf+1,sizeof(buf)-1,argc);
+ buf[len++] = '\r';
+ buf[len++] = '\n';
+ dst = sdscatlen(dst,buf,len);
+
for (j = 0; j < argc; j++) {
- robj *o = getDecodedObject(argv[j]);
- buf = sdscatprintf(buf,"$%lu\r\n",(unsigned long)sdslen(o->ptr));
- buf = sdscatlen(buf,o->ptr,sdslen(o->ptr));
- buf = sdscatlen(buf,"\r\n",2);
+ o = getDecodedObject(argv[j]);
+ buf[0] = '$';
+ len = 1+ll2string(buf+1,sizeof(buf)-1,sdslen(o->ptr));
+ buf[len++] = '\r';
+ buf[len++] = '\n';
+ dst = sdscatlen(dst,buf,len);
+ dst = sdscatlen(dst,o->ptr,sdslen(o->ptr));
+ dst = sdscatlen(dst,"\r\n",2);
decrRefCount(o);
}
- return buf;
+ return dst;
}
sds catAppendOnlyExpireAtCommand(sds buf, robj *key, robj *seconds) {
}
if (buf[0] != '*') goto fmterr;
argc = atoi(buf+1);
+ if (argc < 1) goto fmterr;
+
argv = zmalloc(sizeof(robj*)*argc);
for (j = 0; j < argc; j++) {
if (fgets(buf,sizeof(buf),fp) == NULL) goto readerr;
* Handle this. */
void backgroundRewriteDoneHandler(int exitcode, int bysignal) {
if (!bysignal && exitcode == 0) {
- int fd;
+ int newfd, oldfd;
+ int nwritten;
char tmpfile[256];
+ long long now = ustime();
redisLog(REDIS_NOTICE,
- "Background append only file rewriting terminated with success");
- /* Now it's time to flush the differences accumulated by the parent */
- snprintf(tmpfile,256,"temp-rewriteaof-bg-%d.aof", (int) server.bgrewritechildpid);
- fd = open(tmpfile,O_WRONLY|O_APPEND);
- if (fd == -1) {
- redisLog(REDIS_WARNING, "Not able to open the temp append only file produced by the child: %s", strerror(errno));
+ "Background AOF rewrite terminated with success");
+
+ /* Flush the differences accumulated by the parent to the
+ * rewritten AOF. */
+ snprintf(tmpfile,256,"temp-rewriteaof-bg-%d.aof",
+ (int)server.bgrewritechildpid);
+ newfd = open(tmpfile,O_WRONLY|O_APPEND);
+ if (newfd == -1) {
+ redisLog(REDIS_WARNING,
+ "Unable to open the temporary AOF produced by the child: %s", strerror(errno));
goto cleanup;
}
- /* Flush our data... */
- if (write(fd,server.bgrewritebuf,sdslen(server.bgrewritebuf)) !=
- (signed) sdslen(server.bgrewritebuf)) {
- redisLog(REDIS_WARNING, "Error or short write trying to flush the parent diff of the append log file in the child temp file: %s", strerror(errno));
- close(fd);
+
+ nwritten = write(newfd,server.bgrewritebuf,sdslen(server.bgrewritebuf));
+ if (nwritten != (signed)sdslen(server.bgrewritebuf)) {
+ if (nwritten == -1) {
+ redisLog(REDIS_WARNING,
+ "Error trying to flush the parent diff to the rewritten AOF: %s", strerror(errno));
+ } else {
+ redisLog(REDIS_WARNING,
+ "Short write trying to flush the parent diff to the rewritten AOF: %s", strerror(errno));
+ }
+ close(newfd);
goto cleanup;
}
- redisLog(REDIS_NOTICE,"Parent diff flushed into the new append log file with success (%lu bytes)",sdslen(server.bgrewritebuf));
- /* Now our work is to rename the temp file into the stable file. And
- * switch the file descriptor used by the server for append only. */
+
+ redisLog(REDIS_NOTICE,
+ "Parent diff successfully flushed to the rewritten AOF (%lu bytes)", nwritten);
+
+ /* The only remaining thing to do is to rename the temporary file to
+ * the configured file and switch the file descriptor used to do AOF
+ * writes. We don't want close(2) or rename(2) calls to block the
+ * server on old file deletion.
+ *
+ * There are two possible scenarios:
+ *
+ * 1) AOF is DISABLED and this was a one time rewrite. The temporary
+ * file will be renamed to the configured file. When this file already
+ * exists, it will be unlinked, which may block the server.
+ *
+ * 2) AOF is ENABLED and the rewritten AOF will immediately start
+ * receiving writes. After the temporary file is renamed to the
+ * configured file, the original AOF file descriptor will be closed.
+ * Since this will be the last reference to that file, closing it
+ * causes the underlying file to be unlinked, which may block the
+ * server.
+ *
+ * To mitigate the blocking effect of the unlink operation (either
+ * caused by rename(2) in scenario 1, or by close(2) in scenario 2), we
+ * use a background thread to take care of this. First, we
+ * make scenario 1 identical to scenario 2 by opening the target file
+ * when it exists. The unlink operation after the rename(2) will then
+ * be executed upon calling close(2) for its descriptor. Everything to
+ * guarantee atomicity for this switch has already happened by then, so
+ * we don't care what the outcome or duration of that close operation
+ * is, as long as the file descriptor is released again. */
+ if (server.appendfd == -1) {
+ /* AOF disabled */
+
+ /* Don't care if this fails: oldfd will be -1 and we handle that.
+ * One notable case of -1 return is if the old file does
+ * not exist. */
+ oldfd = open(server.appendfilename,O_RDONLY|O_NONBLOCK);
+ } else {
+ /* AOF enabled */
+ oldfd = -1; /* We'll set this to the current AOF filedes later. */
+ }
+
+ /* Rename the temporary file. This will not unlink the target file if
+ * it exists, because we reference it with "oldfd". */
if (rename(tmpfile,server.appendfilename) == -1) {
- redisLog(REDIS_WARNING,"Can't rename the temp append only file into the stable one: %s", strerror(errno));
- close(fd);
+ redisLog(REDIS_WARNING,
+ "Error trying to rename the temporary AOF: %s", strerror(errno));
+ close(newfd);
+ if (oldfd != -1) close(oldfd);
goto cleanup;
}
- /* Mission completed... almost */
- redisLog(REDIS_NOTICE,"Append only file successfully rewritten.");
- if (server.appendfd != -1) {
- /* If append only is actually enabled... */
- close(server.appendfd);
- server.appendfd = fd;
- if (server.appendfsync != APPENDFSYNC_NO) aof_fsync(fd);
- server.appendseldb = -1; /* Make sure it will issue SELECT */
- redisLog(REDIS_NOTICE,"The new append only file was selected for future appends.");
+
+ if (server.appendfd == -1) {
+ /* AOF disabled, we don't need to set the AOF file descriptor
+ * to this new file, so we can close it. */
+ close(newfd);
+ } else {
+ /* AOF enabled, replace the old fd with the new one. */
+ oldfd = server.appendfd;
+ server.appendfd = newfd;
+ if (server.appendfsync == APPENDFSYNC_ALWAYS)
+ aof_fsync(newfd);
+ else if (server.appendfsync == APPENDFSYNC_EVERYSEC)
+ aof_background_fsync(newfd);
+ server.appendseldb = -1; /* Make sure SELECT is re-issued */
aofUpdateCurrentSize();
server.auto_aofrewrite_base_size = server.appendonly_current_size;
- } else {
- /* If append only is disabled we just generate a dump in this
- * format. Why not? */
- close(fd);
+
+ /* Clear regular AOF buffer since its contents was just written to
+ * the new AOF from the background rewrite buffer. */
+ sdsfree(server.aofbuf);
+ server.aofbuf = sdsempty();
}
+
+ redisLog(REDIS_NOTICE, "Background AOF rewrite successful");
+
+ /* Asynchronously close the overwritten AOF. */
+ if (oldfd != -1) bioCreateBackgroundJob(REDIS_BIO_CLOSE_FILE,(void*)(long)oldfd,NULL,NULL);
+
+ redisLog(REDIS_VERBOSE,
+ "Background AOF rewrite signal handler took %lldus", ustime()-now);
} else if (!bysignal && exitcode != 0) {
- redisLog(REDIS_WARNING, "Background append only file rewriting error");
+ redisLog(REDIS_WARNING,
+ "Background AOF rewrite terminated with error");
} else {
redisLog(REDIS_WARNING,
- "Background append only file rewriting terminated by signal %d",
- bysignal);
+ "Background AOF rewrite terminated by signal %d", bysignal);
}
+
cleanup:
sdsfree(server.bgrewritebuf);
server.bgrewritebuf = sdsempty();
projects / redis.git / commitdiff
