Cluster

Redis CLUSTER SAVECONFIG

Redis Cluster Course	Redis Technical Support	Redis Enterprise Server

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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