Redis篇(2)——main函数

众所周知，redis是C语言写的。那么main函数来一波

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

//运行测试方法
#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], "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,"");
    tzset(); /* Populates 'timezone' global. */
    zmalloc_set_oom_handler(redisOutOfMemoryHandler);
    srand(time(NULL)^getpid());
    gettimeofday(&tv,NULL);

    char hashseed[16];
    getRandomHexChars(hashseed,sizeof(hashseed));
    dictSetHashFunctionSeed((uint8_t*)hashseed);
    server.sentinel_mode = checkForSentinelMode(argc,argv);
    //初始化默认配置
    initServerConfig();
    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. */
    //哨兵模式
    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. */
    //持久化文件检查
    if (strstr(argv[0],"redis-check-rdb") != NULL)
        redis_check_rdb_main(argc,argv,NULL);
    else if (strstr(argv[0],"redis-check-aof") != NULL)
        redis_check_aof_main(argc,argv);

	//加载运行参数/配置文件
    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);
        }
        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();

	//初始化服务器
    initServer();
    if (background || server.pidfile) createPidFile();
    redisSetProcTitle(argv[0]);
    redisAsciiArt();
    checkTcpBacklogSettings();

    if (!server.sentinel_mode) {
        /* Things not needed when running in Sentinel mode. */
        serverLog(LL_WARNING,"Server initialized");
    #ifdef __linux__
        linuxMemoryWarnings();
    #if defined (__arm64__)
        int ret;
        if ((ret = linuxMadvFreeForkBugCheck())) {
            if (ret == 1)
                serverLog(LL_WARNING,"WARNING Your kernel has a bug that could lead to data corruption during background save. "
                                     "Please upgrade to the latest stable kernel.");
            else
                serverLog(LL_WARNING, "Failed to test the kernel for a bug that could lead to data corruption during background save. "
                                      "Your system could be affected, please report this error.");
            if (!checkIgnoreWarning("ARM64-COW-BUG")) {
                serverLog(LL_WARNING,"Redis will now exit to prevent data corruption. "
                                     "Note that it is possible to suppress this warning by setting the following config: ignore-warnings ARM64-COW-BUG");
                exit(1);
            }
        }
    #endif /* __arm64__ */
    #endif /* __linux__ */
        moduleLoadFromQueue();
        InitServerLast();
        //加载持久化文件内容
        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 {
        InitServerLast();
        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);
    }

	//设置事件循环的beforeSleep方法
    aeSetBeforeSleepProc(server.el,beforeSleep);
    //设置事件循环的afterSleep方法
    aeSetAfterSleepProc(server.el,afterSleep);
    //事件循环
    aeMain(server.el);
    //退出循环后释放对应的空间
    aeDeleteEventLoop(server.el);
    return 0;
}

上面贴的直接是源码main方法。下面着重分析以下几点
1、如何加载配置的？
在4266行可以看到initServerChonfig方法
在这里插入图片描述
点进去看可以不难发现这里是redis的默认配置

回到main函数再往下看可以看到，当有配置文件或者启动命令带有的配置参数时会执行loadServerConfig方法覆盖上面initServerConfig的配置

loadServerConfig具体的逻辑这里就贴上去了，大致就是解析配置文件/命令参数的一个取值，赋值的过程。

2、如何监听客户端请求、启动定时任务的？
继续往下看可以看到4377行的 initServer 方法
在这里插入图片描述
initServer主要就是初始化redisServer结构体，监听配置的端口，创建时间事件循环，文件事件循环，打开aof文件等
伪代码如下：
initServer() {

//…

//监听端口
在这里插入图片描述
//…

//创建时间事件监听：redis本身的一些定时任务，比如更新服务器时间缓存、更新LRU时钟、aof命令的追加等操作
//创建文件事件监听：当服务器有连接请求时执行连接处理器acceptTcpHandler的方法。连接处理器会新建一个套接字anetTcpAccept与客户端createClient，同时并监听套接字对应的文件事件与命令处理器readQueryFromClient做绑定用于处理连接后的命令请求。
在这里插入图片描述
//…

//打开aof文件
在这里插入图片描述
//…

}

3、如何加载持久化文件的？
在4407的loadDataFromDisk
在这里插入图片描述
loadDataFromDisk

这个方法一看就知道aof和rdb同时开启的时候会以aof优先加载数据。

4、执行事件循环
aeMain即是对一个一个的事件进行处理。上面提到的时间事件，（连接/命令）文件事件。
在这里插入图片描述

5、写在最后
除此之外，main还有对自带的测试方法、–help，–version等命令，哨兵模式、是否开启了 redis-check-rdb/redis-check-aof 等做了处理。这里就不一一解释了，有兴趣看一眼源码或者是一开始贴的main代码就知道了。