redis主从架构及redis集群

https://redis.io/topics/cluster-spec

Redis Cluster does not support multiple databases like the stand alone version of Redis. There is just database 0 and the SELECT command is not allowed.

31367:M 05 May 13:50:37.300 * DB loaded from disk: 576.582 seconds
31367:M 05 May 13:50:37.300 # You can't have keys in a DB different than DB 0 when in Cluster mode. Exiting.

http://blog.csdn.net/yuyixinye/article/details/41114119

int main(int argc, char **argv) {  
    struct timeval tv;  
  
    /* We need to initialize our libraries, and the server configuration. */  
    // 初始化库  
#ifdef INIT_SETPROCTITLE_REPLACEMENT  
    spt_init(argc, argv);  
#endif  
    setlocale(LC_COLLATE,"");  
    zmalloc_enable_thread_safeness();  
    zmalloc_set_oom_handler(redisOutOfMemoryHandler);  
    srand(time(NULL)^getpid());  
    gettimeofday(&tv,NULL);  
    dictSetHashFunctionSeed(tv.tv_sec^tv.tv_usec^getpid());  
  
    // 检查服务器是否以 Sentinel 模式启动  
    server.sentinel_mode = checkForSentinelMode(argc,argv);  
  
    // 初始化服务器  
    initServerConfig();  
  
    /* We need to init sentinel right now as parsing the configuration file 
     * in sentinel mode will have the effect of populating the sentinel 
     * data structures with master nodes to monitor. */  
    // 如果服务器以 Sentinel 模式启动，那么进行 Sentinel 功能相关的初始化  
    // 并为要监视的主服务器创建一些相应的数据结构  
    if (server.sentinel_mode) {  
        initSentinelConfig();  
        initSentinel();  
    }  
  
    // 检查用户是否指定了配置文件，或者配置选项  
    if (argc >= 2) {  
        int j = 1; /* First option to parse in argv[] */  
        sds options = sdsempty();  
        char *configfile = NULL;  
  
        /* Handle special options --help and --version */  
        // 处理特殊选项 -h 、-v 和 --test-memory  
        if (strcmp(argv[1], "-v") == 0 ||  
            strcmp(argv[1], "--version") == 0) version();  
        if (strcmp(argv[1], "--help") == 0 ||  
            strcmp(argv[1], "-h") == 0) usage();  
        if (strcmp(argv[1], "--test-memory") == 0) {  
            if (argc == 3) {  
                memtest(atoi(argv[2]),50);  
                exit(0);  
            } else {  
                fprintf(stderr,"Please specify the amount of memory to test in megabytes.\n");  
                fprintf(stderr,"Example: ./redis-server --test-memory 4096\n\n");  
                exit(1);  
            }  
        }  
  
        /* First argument is the config file name? */  
        // 如果第一个参数（argv[1]）不是以 "--" 开头  
        // 那么它应该是一个配置文件  
        if (argv[j][0] != '-' || argv[j][1] != '-')  
            configfile = argv[j++];  
  
        /* All the other options are parsed and conceptually appended to the 
         * configuration file. For instance --port 6380 will generate the 
         * string "port 6380\n" to be parsed after the actual file name 
         * is parsed, if any. */  
        // 对用户给定的其余选项进行分析，并将分析所得的字符串追加稍后载入的配置文件的内容之后  
        // 比如 --port 6380 会被分析为 "port 6380\n"  
        while(j != argc) {  
            if (argv[j][0] == '-' && argv[j][1] == '-') {  
                /* Option name */  
                if (sdslen(options)) options = sdscat(options,"\n");  
                options = sdscat(options,argv[j]+2);  
                options = sdscat(options," ");  
            } else {  
                /* Option argument */  
                options = sdscatrepr(options,argv[j],strlen(argv[j]));  
                options = sdscat(options," ");  
            }  
            j++;  
        }  
        if (configfile) server.configfile = getAbsolutePath(configfile);  
        // 重置保存条件  
        resetServerSaveParams();  
  
        // 载入配置文件， options 是前面分析出的给定选项  
        loadServerConfig(configfile,options);  
        sdsfree(options);  
  
        // 获取配置文件的绝对路径  
        if (configfile) server.configfile = getAbsolutePath(configfile);  
    } else {  
        redisLog(REDIS_WARNING, "Warning: no config file specified, using the default config. In order to specify a config file use %s /path/to/%s.conf", argv[0], server.sentinel_mode ? "sentinel" : "redis");  
    }  
  
    // 将服务器设置为守护进程  
    if (server.daemonize) daemonize();  
  
    // 创建并初始化服务器数据结构  
    initServer();  
  
    // 如果服务器是守护进程，那么创建 PID 文件  
    if (server.daemonize) createPidFile();  
  
    // 为服务器进程设置名字  
    redisSetProcTitle(argv[0]);  
  
    // 打印 ASCII LOGO  
    redisAsciiArt();  
  
    // 如果服务器不是运行在 SENTINEL 模式，那么执行以下代码  
    if (!server.sentinel_mode) {  
        /* Things not needed when running in Sentinel mode. */  
        // 打印问候语  
        redisLog(REDIS_WARNING,"Server started, Redis version " REDIS_VERSION);  
    #ifdef __linux__  
        // 打印内存警告  
        linuxOvercommitMemoryWarning();  
    #endif  
        // 从 AOF 文件或者 RDB 文件中载入数据  
        loadDataFromDisk();  
        // 启动集群？  
        if (server.cluster_enabled) {  
            if (verifyClusterConfigWithData() == REDIS_ERR) {  
                redisLog(REDIS_WARNING,  
                    "You can't have keys in a DB different than DB 0 when in "  
                    "Cluster mode. Exiting.");  
                exit(1);  
            }  
        }  
        // 打印 TCP 端口  
        if (server.ipfd_count > 0)  
            redisLog(REDIS_NOTICE,"The server is now ready to accept connections on port %d", server.port);  
        // 打印本地套接字端口  
        if (server.sofd > 0)  
            redisLog(REDIS_NOTICE,"The server is now ready to accept connections at %s", server.unixsocket);  
    } else {  
        sentinelIsRunning();  
    }  
  
    /* Warning the user about suspicious maxmemory setting. */  
    // 检查不正常的 maxmemory 配置  
    if (server.maxmemory > 0 && server.maxmemory < 1024*1024) {  
        redisLog(REDIS_WARNING,"WARNING: You specified a maxmemory value that is less than 1MB (current value is %llu bytes). Are you sure this is what you really want?", server.maxmemory);  
    }  
  
    // 运行事件处理器，一直到服务器关闭为止  
    aeSetBeforeSleepProc(server.el,beforeSleep);  
    aeMain(server.el);  
  
    // 服务器关闭，停止事件循环  
    aeDeleteEventLoop(server.el);  
  
    return 0;  
}