redis源码之main()函数剖析

今天看了redis的源码之中的main()函数，将大概的流程进行梳理。

在代码中进行了相应的注释，便于阅读者理解：

int main(int argc, char **argv) {
    struct timeval tv;
    int j;

#ifdef REDIS_TEST
    if (argc == 3 && !strcasecmp(argv[1], "test")) {
        if (!strcasecmp(argv[2], "ziplist")) {
            return ziplistTest(argc, argv);
        } else if (!strcasecmp(argv[2], "quicklist")) {
            quicklistTest(argc, argv);
        } else if (!strcasecmp(argv[2], "intset")) {
            return intsetTest(argc, argv);
        } else if (!strcasecmp(argv[2], "zipmap")) {
            return zipmapTest(argc, argv);
        } else if (!strcasecmp(argv[2], "sha1test")) {
            return sha1Test(argc, argv);
        } else if (!strcasecmp(argv[2], "util")) {
            return utilTest(argc, argv);
        } else if (!strcasecmp(argv[2], "sds")) {
            return sdsTest(argc, argv);
        } else if (!strcasecmp(argv[2], "endianconv")) {
            return endianconvTest(argc, argv);
        } else if (!strcasecmp(argv[2], "crc64")) {
            return crc64Test(argc, argv);
        } else if (!strcasecmp(argv[2], "zmalloc")) {
            return zmalloc_test(argc, argv);
        }

        return -1; /* test not found */
    }
#endif

    /* We need to initialize our libraries, and the server configuration. */
#ifdef INIT_SETPROCTITLE_REPLACEMENT
    spt_init(argc, argv);
#endif
    setlocale(LC_COLLATE,"");  //更改字符编码
    tzset(); /* Populates 'timezone' global. */

    // oom时的处理,主要是内存不足时，将需要的memory的值打印出来
    zmalloc_set_oom_handler(redisOutOfMemoryHandler);

    // 根据当前时间和pid获取随机值的
    srand(time(NULL)^getpid());
    gettimeofday(&tv,NULL);  // 1970年1月1日到现在的时间

    char hashseed[16];
    //获取哈希种子
    getRandomHexChars(hashseed,sizeof(hashseed));
    dictSetHashFunctionSeed((uint8_t*)hashseed);

    // 服务器的启动模式：单机模式、Cluster模式、sentinel模式
    server.sentinel_mode = checkForSentinelMode(argc,argv);

    // 服务器端的配置
    initServerConfig();
    ACLInit(); /* The ACL subsystem must be initialized ASAP because the
                  basic networking code and client creation depends on it. */
    moduleInitModulesSystem();

    /* Store the executable path and arguments in a safe place in order
     * to be able to restart the server later. */
    server.executable = getAbsolutePath(argv[0]);
    server.exec_argv = zmalloc(sizeof(char*)*(argc+1));
    server.exec_argv[argc] = NULL;
    for (j = 0; j < argc; j++) server.exec_argv[j] = zstrdup(argv[j]);

    /* 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. */

    // sentinel模式下的配置
    if (server.sentinel_mode) {
        initSentinelConfig();
        initSentinel();
    }

    /* Check if we need to start in redis-check-rdb/aof mode. We just execute
     * the program main. However the program is part of the Redis executable
     * so that we can easily execute an RDB check on loading errors. */
    // 持久化的两种方式
    if (strstr(argv[0],"redis-check-rdb") != NULL)
        // 定期的将数据dump到磁盘中
        redis_check_rdb_main(argc,argv,NULL);
    else if (strstr(argv[0],"redis-check-aof") != NULL)
        // 通过aof记录事务执行的每个命令，便于数据的恢复
        redis_check_aof_main(argc,argv);

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

        /* 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);
            }
        }

        /* First argument is the config file name? */
        if (argv[j][0] != '-' || argv[j][1] != '-') {
            configfile = argv[j];
            server.configfile = getAbsolutePath(configfile);
            /* Replace the config file in server.exec_argv with
             * its absolute path. */
            zfree(server.exec_argv[j]);
            server.exec_argv[j] = zstrdup(server.configfile);
            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 (!strcmp(argv[j], "--check-rdb")) {
                    /* Argument has no options, need to skip for parsing. */
                    j++;
                    continue;
                }
                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 == '-') {
            serverLog(LL_WARNING,
                "Sentinel config from STDIN not allowed.");
            serverLog(LL_WARNING,
                "Sentinel needs config file on disk to save state.  Exiting...");
            exit(1);
        }

        // 释放内存 
        resetServerSaveParams();
        loadServerConfig(configfile,options);
        sdsfree(options);
    }

    serverLog(LL_WARNING, "oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo");
    serverLog(LL_WARNING,
        "Redis version=%s, bits=%d, commit=%s, modified=%d, pid=%d, just started",
            REDIS_VERSION,
            (sizeof(long) == 8) ? 64 : 32,
            redisGitSHA1(),
            strtol(redisGitDirty(),NULL,10) > 0,
            (int)getpid());

    if (argc == 1) {
        serverLog(LL_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");
    } else {
        serverLog(LL_WARNING, "Configuration loaded");
    }

    server.supervised = redisIsSupervised(server.supervised_mode);
    int background = server.daemonize && !server.supervised;
    if (background) daemonize();

    //sever端的初始化
    initServer();
    if (background || server.pidfile) createPidFile();

    // 设置进程的title
    redisSetProcTitle(argv[0]);
    redisAsciiArt();
    checkTcpBacklogSettings();

    // 非sentinel模式
    if (!server.sentinel_mode) {
        /* Things not needed when running in Sentinel mode. */
        serverLog(LL_WARNING,"Server initialized");
    #ifdef __linux__
        linuxMemoryWarnings();
    #endif
        moduleLoadFromQueue();
        ACLLoadUsersAtStartup();

        // 从磁盘获取已经持久化的数据
        loadDataFromDisk();
        if (server.cluster_enabled) {
            if (verifyClusterConfigWithData() == C_ERR) {
                serverLog(LL_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)
            serverLog(LL_NOTICE,"Ready to accept connections");
        if (server.sofd > 0)
            serverLog(LL_NOTICE,"The server is now ready to accept connections at %s", server.unixsocket);
    } else {
        // 检测sentinel的配置是否有效
        sentinelIsRunning();
    }

    /* Warning the user about suspicious maxmemory setting. */
    if (server.maxmemory > 0 && server.maxmemory < 1024*1024) {
        serverLog(LL_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);
    }

    // 设置服务器sleep之前的函数调用
    aeSetBeforeSleepProc(server.el,beforeSleep);

    // 设置服务器sleep后的函数调用
    aeSetAfterSleepProc(server.el,afterSleep);

    // 主函数事件驱动
    aeMain(server.el);

    // 删除事件驱动
    aeDeleteEventLoop(server.el);
    return 0;
}

阅读了main()函数中的源码之后发现redis居然有OOM机制，内存分配不出来时，将申请的内存打印出来等等。由于本人能力有限只能理解到这里。后续继续分析redis源码。