Cluster

Redis CLUSTER SAVECONFIG

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Redis CLUSTER SAVECONFIG

CLUSTER SAVECONFIG은 nodes.conf 파일에 클러스터의 노드 정보를 저장하는 명령이다.
클러스터의 상태가 바뀌면 자동으로 저장한다. 이것은 수동으로 저장하는 명령이다.

이 문서는 버전 3.2.0을 기준으로 만들었습니다.

소스 코드

cluster.c

void clusterCommand(client *c) {
	...
    if (!strcasecmp(c->argv[1]->ptr,"saveconfig") && c->argc == 2) {
        int retval = clusterSaveConfig(1);

        if (retval == 0)
            addReply(c,shared.ok);
        else
            addReplyErrorFormat(c,"error saving the cluster node config: %s",
                strerror(errno));
    } 
} 

/* Cluster node configuration is exactly the same as CLUSTER NODES output.
 *
 * This function writes the node config and returns 0, on error -1
 * is returned.
 *
 * Note: we need to write the file in an atomic way from the point of view
 * of the POSIX filesystem semantics, so that if the server is stopped
 * or crashes during the write, we'll end with either the old file or the
 * new one. Since we have the full payload to write available we can use
 * a single write to write the whole file. If the pre-existing file was
 * bigger we pad our payload with newlines that are anyway ignored and truncate
 * the file afterward. */
int clusterSaveConfig(int do_fsync) {
    sds ci;
    size_t content_size;
    struct stat sb;
    int fd;

    server.cluster->todo_before_sleep &= ~CLUSTER_TODO_SAVE_CONFIG;

    /* Get the nodes description and concatenate our "vars" directive to
     * save currentEpoch and lastVoteEpoch. */
    ci = clusterGenNodesDescription(CLUSTER_NODE_HANDSHAKE);
    ci = sdscatprintf(ci,"vars currentEpoch %llu lastVoteEpoch %llu\n",
        (unsigned long long) server.cluster->currentEpoch,
        (unsigned long long) server.cluster->lastVoteEpoch);
    content_size = sdslen(ci);

    if ((fd = open(server.cluster_configfile,O_WRONLY|O_CREAT,0644))
        == -1) goto err;

    /* Pad the new payload if the existing file length is greater. */
    if (fstat(fd,&sb) != -1) {
        if (sb.st_size > (off_t)content_size) {
            ci = sdsgrowzero(ci,sb.st_size);
            memset(ci+content_size,'\n',sb.st_size-content_size);
        }
    }
    if (write(fd,ci,sdslen(ci)) != (ssize_t)sdslen(ci)) goto err;
    if (do_fsync) {
        server.cluster->todo_before_sleep &= ~CLUSTER_TODO_FSYNC_CONFIG;
        fsync(fd);
    }

    /* Truncate the file if needed to remove the final \n padding that
     * is just garbage. */
    if (content_size != sdslen(ci) && ftruncate(fd,content_size) == -1) {
        /* ftruncate() failing is not a critical error. */
    }
    close(fd);
    sdsfree(ci);
    return 0;

err:
    if (fd != -1) close(fd);
    sdsfree(ci);
    return -1;
}

void clusterSaveConfigOrDie(int do_fsync) {
    if (clusterSaveConfig(do_fsync) == -1) {
        serverLog(LL_WARNING,"Fatal: can't update cluster config file.");
        exit(1);
    }
}

명령문

CLUSTER SAVECONFIG

이 명령은 version 3.0.0 부터 사용할 수 있다.
논리적 처리 소요시간은 O(1)이다.

Clients for Java	Jedis, Lettuce
Clients for C	Hiredis

<< CLUSTER RESET	CLUSTER SAVECONFIG	CLUSTER SET-CONFIG-EPOCH >>

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