redis3.0.7源码阅读(十三)main函数

版本：3.0.7

源码：redis.c

/*
 * main函数
 */
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());

    // 检查是否sentinel模式
    server.sentinel_mode = checkForSentinelMode(argc,argv);

    // 初始化服务器配置项
    initServerConfig();

    // 初始化sentinel
    /* 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. */
    if (server.sentinel_mode) {
        initSentinelConfig();
        initSentinel();
    }

    if (argc >= 2) {
        int j = 1; /* First option to parse in argv[] */
        sds options = sdsempty();
        char *configfile = NULL;

        // 处理-v/--version/-h/--help/--test-memory
        /* Handle special options --help and --version */
        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);
            }
        }

        // 检查用户是否指定了配置文件，或者配置选项
        /* First argument is the config file name? */
        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. */
        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 (server.sentinel_mode && configfile && *configfile == '-') {
            redisLog(REDIS_WARNING,
                "Sentinel config from STDIN not allowed.");
            redisLog(REDIS_WARNING,
                "Sentinel needs config file on disk to save state.  Exiting...");
            exit(1);
        }
        if (configfile) server.configfile = getAbsolutePath(configfile);
        resetServerSaveParams();

        // 加载配置
        loadServerConfig(configfile,options);
        sdsfree(options);
    } 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");
    }

    // 守护模式
    if (server.daemonize) daemonize();

    // 初始化服务器
    initServer();

    // 守护模式创建PID文件
    if (server.daemonize) createPidFile();

    // 进程环境相关设置，设置名字
    redisSetProcTitle(argv[0]);
    
    // 打印 ASCII LOGO
    redisAsciiArt();
    
    // 检查内核backlog参数支持
    checkTcpBacklogSettings();

    if (!server.sentinel_mode) {
        /* Things not needed when running in Sentinel mode. */
        // 打印服务器启动成功
        redisLog(REDIS_WARNING,"Server started, Redis version " REDIS_VERSION);
    #ifdef __linux__
        // 检查内存分配策略，并打印警告
        linuxMemoryWarnings();
    #endif
        // 加载持久化文件
        loadDataFromDisk();

        // 如果是集群模式，检查加载的数据是否正确
        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);
            }
        }
        if (server.ipfd_count > 0)
            redisLog(REDIS_NOTICE,"The server is now ready to accept connections on port %d", server.port);
        if (server.sofd > 0)
            redisLog(REDIS_NOTICE,"The server is now ready to accept connections at %s", server.unixsocket);
    } else {

        // sentnel模式启动
        sentinelIsRunning();
    }

    // 设置的max内存小于1MB，提醒用户
    /* Warning the user about suspicious maxmemory setting. */
    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);
    }

    // 设置事件处理之前需要调用的函数
    aeSetBeforeSleepProc(server.el,beforeSleep);
    
    // 开始事件循环
    /*
     * 调用链举例
     * initServer()：aeCreateFileEvent注册acceptTcpHandler事件
     * 当客户端请求来临时：acceptTcpHandler->anetTcpAccept
     * 连接建立成功后，创建客户端：acceptCommonHandler->createClient
     * 创建客户端成功后：aeCreateFileEvent注册readQueryFromClient
     * 执行客户端命令：readQueryFromClient->processInputBuffer->processCommand
     * 在processCommand中通过lookupCommand找到命令对应的执行函数设置c->cmd，在一系列的判断后，调用call函数执行命令
     * call函数会执行c->cmd->proc(c)：在proc中会执行，比如proc是getCommand，在getCommand中会执行addReply函数
     * addReply函数是返回输出给客户端的底层调用，此函数会增加写事件sendReplyToClient到多路复用库中
     * 关于事件管理：每次执行1000次接收连接(acceptTcpHandler)，每次将所有的就绪事件都处理了(aeApiPoll函数)
     */ 
    aeMain(server.el);

    // 服务器关闭，停止事件循环
    aeDeleteEventLoop(server.el);
    return 0;
}

原文出自：http://blog.youkuaiyun.com/daiyudong2020/article/details/54237076

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