Gossip about redis source code 73

Load the information in the configuration file , Non emphasis ：

/* Load the cluster config from 'filename'.
 *
 * If the file does not exist or is zero-length (this may happen because
 * when we lock the nodes.conf file, we create a zero-length one for the
 * sake of locking if it does not already exist), C_ERR is returned.
 * If the configuration was loaded from the file, C_OK is returned. */
int clusterLoadConfig(char *filename) {
    FILE *fp = fopen(filename,"r");
    struct stat sb;
    char *line;
    int maxline, j;

    if (fp == NULL) {
        if (errno == ENOENT) {
            return C_ERR;
        } else {
            serverLog(LL_WARNING,
                "Loading the cluster node config from %s: %s",
                filename, strerror(errno));
            exit(1);
        }
    }

    /* Check if the file is zero-length: if so return C_ERR to signal
     * we have to write the config. */
    if (fstat(fileno(fp),&sb) != -1 && sb.st_size == 0) {
        fclose(fp);
        return C_ERR;
    }

    /* Parse the file. Note that single lines of the cluster config file can
     * be really long as they include all the hash slots of the node.
     * This means in the worst possible case, half of the Redis slots will be
     * present in a single line, possibly in importing or migrating state, so
     * together with the node ID of the sender/receiver.
     *
     * To simplify we allocate 1024+CLUSTER_SLOTS*128 bytes per line. */
    maxline = 1024+CLUSTER_SLOTS*128;
    line = zmalloc(maxline);
    while(fgets(line,maxline,fp) != NULL) {
        int argc;
        sds *argv;
        clusterNode *n, *master;
        char *p, *s;

        /* Skip blank lines, they can be created either by users manually
         * editing nodes.conf or by the config writing process if stopped
         * before the truncate() call. */
        if (line[0] == '\n' || line[0] == '\0') continue;

        /* Split the line into arguments for processing. */
        argv = sdssplitargs(line,&argc);
        if (argv == NULL) goto fmterr;

        /* Handle the special "vars" line. Don't pretend it is the last
         * line even if it actually is when generated by Redis. */
        if (strcasecmp(argv[0],"vars") == 0) {
            if (!(argc % 2)) goto fmterr;
            for (j = 1; j < argc; j += 2) {
                if (strcasecmp(argv[j],"currentEpoch") == 0) {
                    server.cluster->currentEpoch =
                            strtoull(argv[j+1],NULL,10);
                } else if (strcasecmp(argv[j],"lastVoteEpoch") == 0) {
                    server.cluster->lastVoteEpoch =
                            strtoull(argv[j+1],NULL,10);
                } else {
                    serverLog(LL_WARNING,
                        "Skipping unknown cluster config variable '%s'",
                        argv[j]);
                }
            }
            sdsfreesplitres(argv,argc);
            continue;
        }

        /* Regular config lines have at least eight fields */
        if (argc < 8) {
            sdsfreesplitres(argv,argc);
            goto fmterr;
        }

        /* Create this node if it does not exist */
        n = clusterLookupNode(argv[0]);
        if (!n) {
            n = createClusterNode(argv[0],0);
            clusterAddNode(n);
        }
        /* Address and port */
        if ((p = strrchr(argv[1],':')) == NULL) {
            sdsfreesplitres(argv,argc);
            goto fmterr;
        }
        *p = '\0';
        memcpy(n->ip,argv[1],strlen(argv[1])+1);
        char *port = p+1;
        char *busp = strchr(port,'@');
        if (busp) {
            *busp = '\0';
            busp++;
        }
        n->port = atoi(port);
        /* In older versions of nodes.conf the "@busport" part is missing.
         * In this case we set it to the default offset of 10000 from the
         * base port. */
        n->cport = busp ? atoi(busp) : n->port + CLUSTER_PORT_INCR;

        /* The plaintext port for client in a TLS cluster (n->pport) is not
         * stored in nodes.conf. It is received later over the bus protocol. */

        /* Parse flags */
        p = s = argv[2];
        while(p) {
            p = strchr(s,',');
            if (p) *p = '\0';
            if (!strcasecmp(s,"myself")) {
                serverAssert(server.cluster->myself == NULL);
                myself = server.cluster->myself = n;
                n->flags |= CLUSTER_NODE_MYSELF;
            } else if (!strcasecmp(s,"master")) {
                n->flags |= CLUSTER_NODE_MASTER;
            } else if (!strcasecmp(s,"slave")) {
                n->flags |= CLUSTER_NODE_SLAVE;
            } else if (!strcasecmp(s,"fail?")) {
                n->flags |= CLUSTER_NODE_PFAIL;
            } else if (!strcasecmp(s,"fail")) {
                n->flags |= CLUSTER_NODE_FAIL;
                n->fail_time = mstime();
            } else if (!strcasecmp(s,"handshake")) {
                n->flags |= CLUSTER_NODE_HANDSHAKE;
            } else if (!strcasecmp(s,"noaddr")) {
                n->flags |= CLUSTER_NODE_NOADDR;
            } else if (!strcasecmp(s,"nofailover")) {
                n->flags |= CLUSTER_NODE_NOFAILOVER;
            } else if (!strcasecmp(s,"noflags")) {
                /* nothing to do */
            } else {
                serverPanic("Unknown flag in redis cluster config file");
            }
            if (p) s = p+1;
        }

        /* Get master if any. Set the master and populate master's
         * slave list. */
        if (argv[3][0] != '-') {
            master = clusterLookupNode(argv[3]);
            if (!master) {
                master = createClusterNode(argv[3],0);
                clusterAddNode(master);
            }
            n->slaveof = master;
            clusterNodeAddSlave(master,n);
        }

        /* Set ping sent / pong received timestamps */
        if (atoi(argv[4])) n->ping_sent = mstime();
        if (atoi(argv[5])) n->pong_received = mstime();

        /* Set configEpoch for this node. */
        n->configEpoch = strtoull(argv[6],NULL,10);

        /* Populate hash slots served by this instance. */
        for (j = 8; j < argc; j++) {
            int start, stop;

            if (argv[j][0] == '[') {
                /* Here we handle migrating / importing slots */
                int slot;
                char direction;
                clusterNode *cn;

                p = strchr(argv[j],'-');
                serverAssert(p != NULL);
                *p = '\0';
                direction = p[1]; /* Either '>' or '<' */
                slot = atoi(argv[j]+1);
                if (slot < 0 || slot >= CLUSTER_SLOTS) {
                    sdsfreesplitres(argv,argc);
                    goto fmterr;
                }
                p += 3;
                cn = clusterLookupNode(p);
                if (!cn) {
                    cn = createClusterNode(p,0);
                    clusterAddNode(cn);
                }
                if (direction == '>') {
                    server.cluster->migrating_slots_to[slot] = cn;
                } else {
                    server.cluster->importing_slots_from[slot] = cn;
                }
                continue;
            } else if ((p = strchr(argv[j],'-')) != NULL) {
                *p = '\0';
                start = atoi(argv[j]);
                stop = atoi(p+1);
            } else {
                start = stop = atoi(argv[j]);
            }
            if (start < 0 || start >= CLUSTER_SLOTS ||
                stop < 0 || stop >= CLUSTER_SLOTS)
            {
                sdsfreesplitres(argv,argc);
                goto fmterr;
            }
            while(start <= stop) clusterAddSlot(n, start++);
        }

        sdsfreesplitres(argv,argc);
    }
    /* Config sanity check */
    if (server.cluster->myself == NULL) goto fmterr;

    zfree(line);
    fclose(fp);

    serverLog(LL_NOTICE,"Node configuration loaded, I'm %.40s", myself->name);

    /* Something that should never happen: currentEpoch smaller than
     * the max epoch found in the nodes configuration. However we handle this
     * as some form of protection against manual editing of critical files. */
    if (clusterGetMaxEpoch() > server.cluster->currentEpoch) {
        server.cluster->currentEpoch = clusterGetMaxEpoch();
    }
    return C_OK;

fmterr:
    serverLog(LL_WARNING,
        "Unrecoverable error: corrupted cluster config file.");
    zfree(line);
    if (fp) fclose(fp);
    exit(1);
}

/* 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, 0);
    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;
        if (fsync(fd) == -1) goto err;
    }

    /* 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);
    }
}

/* Lock the cluster config using flock(), and leaks the file descriptor used to
 * acquire the lock so that the file will be locked forever.
 *
 * This works because we always update nodes.conf with a new version
 * in-place, reopening the file, and writing to it in place (later adjusting
 * the length with ftruncate()).
 *
 * On success C_OK is returned, otherwise an error is logged and
 * the function returns C_ERR to signal a lock was not acquired. */
int clusterLockConfig(char *filename) {
/* flock() does not exist on Solaris
 * and a fcntl-based solution won't help, as we constantly re-open that file,
 * which will release _all_ locks anyway
 */
#if !defined(__sun)
    /* To lock it, we need to open the file in a way it is created if
     * it does not exist, otherwise there is a race condition with other
     * processes. */
    int fd = open(filename,O_WRONLY|O_CREAT|O_CLOEXEC,0644);
    if (fd == -1) {
        serverLog(LL_WARNING,
            "Can't open %s in order to acquire a lock: %s",
            filename, strerror(errno));
        return C_ERR;
    }

    if (flock(fd,LOCK_EX|LOCK_NB) == -1) {
        if (errno == EWOULDBLOCK) {
            serverLog(LL_WARNING,
                 "Sorry, the cluster configuration file %s is already used "
                 "by a different Redis Cluster node. Please make sure that "
                 "different nodes use different cluster configuration "
                 "files.", filename);
        } else {
            serverLog(LL_WARNING,
                "Impossible to lock %s: %s", filename, strerror(errno));
        }
        close(fd);
        return C_ERR;
    }
    /* Lock acquired: leak the 'fd' by not closing it, so that we'll retain the
     * lock to the file as long as the process exists.
     *
     * After fork, the child process will get the fd opened by the parent process,
     * we need save `fd` to `cluster_config_file_lock_fd`, so that in redisFork(),
     * it will be closed in the child process.
     * If it is not closed, when the main process is killed -9, but the child process
     * (redis-aof-rewrite) is still alive, the fd(lock) will still be held by the
     * child process, and the main process will fail to get lock, means fail to start. */
    server.cluster_config_file_lock_fd = fd;
#else
    UNUSED(filename);
#endif /* __sun */

    return C_OK;
}

/* Derives our ports to be announced in the cluster bus. */
void deriveAnnouncedPorts(int *announced_port, int *announced_pport,
                          int *announced_cport) {
    int port = server.tls_cluster ? server.tls_port : server.port;
    /* Default announced ports. */
    *announced_port = port;
    *announced_pport = server.tls_cluster ? server.port : 0;
    *announced_cport = port + CLUSTER_PORT_INCR;
    /* Config overriding announced ports. */
    if (server.tls_cluster && server.cluster_announce_tls_port) {
        *announced_port = server.cluster_announce_tls_port;
        *announced_pport = server.cluster_announce_port;
    } else if (server.cluster_announce_port) {
        *announced_port = server.cluster_announce_port;
    }
    if (server.cluster_announce_bus_port) {
        *announced_cport = server.cluster_announce_bus_port;
    }
}

/* Some flags (currently just the NOFAILOVER flag) may need to be updated
 * in the "myself" node based on the current configuration of the node,
 * that may change at runtime via CONFIG SET. This function changes the
 * set of flags in myself->flags accordingly. */
void clusterUpdateMyselfFlags(void) {
    int oldflags = myself->flags;
    int nofailover = server.cluster_slave_no_failover ?
                     CLUSTER_NODE_NOFAILOVER : 0;
    myself->flags &= ~CLUSTER_NODE_NOFAILOVER;
    myself->flags |= nofailover;
    if (myself->flags != oldflags) {
        clusterDoBeforeSleep(CLUSTER_TODO_SAVE_CONFIG|
                             CLUSTER_TODO_UPDATE_STATE);
    }
}

void clusterInit(void) {
    int saveconf = 0;

    server.cluster = zmalloc(sizeof(clusterState));
    server.cluster->myself = NULL;
    server.cluster->currentEpoch = 0;
    server.cluster->state = CLUSTER_FAIL;
    server.cluster->size = 1;
    server.cluster->todo_before_sleep = 0;
    server.cluster->nodes = dictCreate(&clusterNodesDictType,NULL);
    server.cluster->nodes_black_list =
        dictCreate(&clusterNodesBlackListDictType,NULL);
    server.cluster->failover_auth_time = 0;
    server.cluster->failover_auth_count = 0;
    server.cluster->failover_auth_rank = 0;
    server.cluster->failover_auth_epoch = 0;
    server.cluster->cant_failover_reason = CLUSTER_CANT_FAILOVER_NONE;
    server.cluster->lastVoteEpoch = 0;
    for (int i = 0; i < CLUSTERMSG_TYPE_COUNT; i++) {
        server.cluster->stats_bus_messages_sent[i] = 0;
        server.cluster->stats_bus_messages_received[i] = 0;
    }
    server.cluster->stats_pfail_nodes = 0;
    memset(server.cluster->slots,0, sizeof(server.cluster->slots));
    clusterCloseAllSlots();

    /* Lock the cluster config file to make sure every node uses
     * its own nodes.conf. */
    server.cluster_config_file_lock_fd = -1;
    if (clusterLockConfig(server.cluster_configfile) == C_ERR)
        exit(1);

    /* Load or create a new nodes configuration. */
    if (clusterLoadConfig(server.cluster_configfile) == C_ERR) {
        /* No configuration found. We will just use the random name provided
         * by the createClusterNode() function. */
        myself = server.cluster->myself =
            createClusterNode(NULL,CLUSTER_NODE_MYSELF|CLUSTER_NODE_MASTER);
        serverLog(LL_NOTICE,"No cluster configuration found, I'm %.40s",
            myself->name);
        clusterAddNode(myself);
        saveconf = 1;
    }
    if (saveconf) clusterSaveConfigOrDie(1);

    /* We need a listening TCP port for our cluster messaging needs. */
    server.cfd.count = 0;

    /* Port sanity check II
     * The other handshake port check is triggered too late to stop
     * us from trying to use a too-high cluster port number. */
    int port = server.tls_cluster ? server.tls_port : server.port;
    if (port > (65535-CLUSTER_PORT_INCR)) {
        serverLog(LL_WARNING, "Redis port number too high. "
                   "Cluster communication port is 10,000 port "
                   "numbers higher than your Redis port. "
                   "Your Redis port number must be 55535 or less.");
        exit(1);
    }
    if (listenToPort(port+CLUSTER_PORT_INCR, &server.cfd) == C_ERR) {
        exit(1);
    }
    if (createSocketAcceptHandler(&server.cfd, clusterAcceptHandler) != C_OK) {
        serverPanic("Unrecoverable error creating Redis Cluster socket accept handler.");
    }

    /* The slots -> keys map is a radix tree. Initialize it here. */
    server.cluster->slots_to_keys = raxNew();
    memset(server.cluster->slots_keys_count,0,
           sizeof(server.cluster->slots_keys_count));

    /* Set myself->port/cport/pport to my listening ports, we'll just need to
     * discover the IP address via MEET messages. */
    deriveAnnouncedPorts(&myself->port, &myself->pport, &myself->cport);

    server.cluster->mf_end = 0;
    resetManualFailover();
    clusterUpdateMyselfFlags();
}