* 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. 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 in libeio 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 */
+ struct stat st;
+
+ /* Check if the configured filename exists. If so, we need to open
+ * it to prevent rename(2) from unlinking it. */
+ if (stat(server.appendfilename, &st) == ENOENT) {
+ oldfd = -1;
+ } else {
+ /* Don't care if this fails: oldfd will be -1. */
+ oldfd = open(server.appendfilename,O_RDONLY|O_NONBLOCK);
+ }
+ } else {
+ /* AOF enabled */
+ oldfd = -1;
+ }
+
+ /* 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 */
+ close(newfd);
+ } else {
+ /* AOF enabled */
+ oldfd = server.appendfd;
+ server.appendfd = newfd;
+ if (server.appendfsync != APPENDFSYNC_NO) aof_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);
}
+
+ redisLog(REDIS_NOTICE, "Background AOF rewrite successful");
+
+ /* Asynchronously close the overwritten AOF. */
+ if (oldfd != -1) eio_close(oldfd, 0, NULL, 0);
+
+ 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
