Function getRDB

app/redis-6.2.6/src/redis-cli.c:7195–7287

This function implements --rdb, so it uses the replication protocol in order * to fetch the RDB file from a remote server. */

/* This function implements --rdb, so it uses the replication protocol in order
 * to fetch the RDB file from a remote server. */
static void getRDB(clusterManagerNode *node) {
    int fd;
    redisContext *s;
    char *filename;
    if (node != NULL) {
        assert(node->context);
        s = node->context;
        filename = clusterManagerGetNodeRDBFilename(node);
    } else {
        s = context;
        filename = config.rdb_filename;
    }
    static char eofmark[RDB_EOF_MARK_SIZE];
    static char lastbytes[RDB_EOF_MARK_SIZE];
    static int usemark = 0;
    unsigned long long payload = sendSync(s, eofmark);
    char buf[4096];

    if (payload == 0) {
        payload = ULLONG_MAX;
        memset(lastbytes,0,RDB_EOF_MARK_SIZE);
        usemark = 1;
        fprintf(stderr,"SYNC sent to master, writing bytes of bulk transfer "
                "until EOF marker to '%s'\n", filename);
    } else {
        fprintf(stderr,"SYNC sent to master, writing %llu bytes to '%s'\n",
            payload, filename);
    }

    int write_to_stdout = !strcmp(filename,"-");
    /* Write to file. */
    if (write_to_stdout) {
        fd = STDOUT_FILENO;
    } else {
        fd = open(filename, O_CREAT|O_WRONLY, 0644);
        if (fd == -1) {
            fprintf(stderr, "Error opening '%s': %s\n", filename,
                strerror(errno));
            exit(1);
        }
    }

    while(payload) {
        ssize_t nread, nwritten;

        nread = readConn(s,buf,(payload > sizeof(buf)) ? sizeof(buf) : payload);
        if (nread <= 0) {
            fprintf(stderr,"I/O Error reading RDB payload from socket\n");
            exit(1);
        }
        nwritten = write(fd, buf, nread);
        if (nwritten != nread) {
            fprintf(stderr,"Error writing data to file: %s\n",
                (nwritten == -1) ? strerror(errno) : "short write");
            exit(1);
        }
        payload -= nread;