Redis源码解析（二）：redis之服务器-redis.c

    我们一次来看这份代码，揭开redis服务器的神秘面纱。

    首先是命令映射表：

/*命令映射表，参数1：命令，参数2：指向实现此命令的函数，参数3：参数个数，参数4：标志位（具体信息看注释），
 *参数5：从参数4计算而得到的字节掩码，参数6：作为可选项的获取键值的函数，参数7：第一个索引位置，参数8：最后一个索引位置
 *参数9：增量，参数10：命令执行时间，参数11：命令调用次数
 */
struct redisCommand redisCommandTable[] = {
    //获取字符串命令
    {"get",getCommand,2,"rF",0,NULL,1,1,1,0,0},
    //设置字符串命令
    {"set",setCommand,-3,"wm",0,NULL,1,1,1,0,0},
    //当且仅当key不存在的情况设置字符串
    {"setnx",setnxCommand,3,"wmF",0,NULL,1,1,1,0,0},
    //当且仅当key存在的情况设置字符串，生存时间为秒级
    {"setex",setexCommand,4,"wm",0,NULL,1,1,1,0,0},
    //设置字符串，生存时间为毫秒级
    {"psetex",psetexCommand,4,"wm",0,NULL,1,1,1,0,0},
    //如果key存在则在末尾加如果不存在就相当于set
    {"append",appendCommand,3,"wm",0,NULL,1,1,1,0,0},
    //字符串长度
    {"strlen",strlenCommand,2,"rF",0,NULL,1,1,1,0,0},
    //删除一个或多个key
    {"del",delCommand,-2,"w",0,NULL,1,-1,1,0,0},
    //判断key是否存在
    {"exists",existsCommand,2,"rF",0,NULL,1,1,1,0,0},
    //当key存在时清除偏移量后面的值，否则自动生成新字符串
    {"setbit",setbitCommand,4,"wm",0,NULL,1,1,1,0,0},
    //获取指定偏移量后的位
    {"getbit",getbitCommand,3,"rF",0,NULL,1,1,1,0,0},
    {"setrange",setrangeCommand,4,"wm",0,NULL,1,1,1,0,0},
    {"getrange",getrangeCommand,4,"r",0,NULL,1,1,1,0,0},
    {"substr",getrangeCommand,4,"r",0,NULL,1,1,1,0,0},
    {"incr",incrCommand,2,"wmF",0,NULL,1,1,1,0,0},
    {"decr",decrCommand,2,"wmF",0,NULL,1,1,1,0,0},
    {"mget",mgetCommand,-2,"r",0,NULL,1,-1,1,0,0},
    {"rpush",rpushCommand,-3,"wmF",0,NULL,1,1,1,0,0},
    {"lpush",lpushCommand,-3,"wmF",0,NULL,1,1,1,0,0},
    {"rpushx",rpushxCommand,3,"wmF",0,NULL,1,1,1,0,0},
    {"lpushx",lpushxCommand,3,"wmF",0,NULL,1,1,1,0,0},
    {"linsert",linsertCommand,5,"wm",0,NULL,1,1,1,0,0},
    {"rpop",rpopCommand,2,"wF",0,NULL,1,1,1,0,0},
    {"lpop",lpopCommand,2,"wF",0,NULL,1,1,1,0,0},
    {"brpop",brpopCommand,-3,"ws",0,NULL,1,1,1,0,0},
    {"brpoplpush",brpoplpushCommand,4,"wms",0,NULL,1,2,1,0,0},
    {"blpop",blpopCommand,-3,"ws",0,NULL,1,-2,1,0,0},
    {"llen",llenCommand,2,"rF",0,NULL,1,1,1,0,0},
    {"lindex",lindexCommand,3,"r",0,NULL,1,1,1,0,0},
    {"lset",lsetCommand,4,"wm",0,NULL,1,1,1,0,0},
    {"lrange",lrangeCommand,4,"r",0,NULL,1,1,1,0,0},
    {"ltrim",ltrimCommand,4,"w",0,NULL,1,1,1,0,0},
    {"lrem",lremCommand,4,"w",0,NULL,1,1,1,0,0},
    {"rpoplpush",rpoplpushCommand,3,"wm",0,NULL,1,2,1,0,0},
    {"sadd",saddCommand,-3,"wmF",0,NULL,1,1,1,0,0},
    {"srem",sremCommand,-3,"wF",0,NULL,1,1,1,0,0},
    {"smove",smoveCommand,4,"wF",0,NULL,1,2,1,0,0},
    {"sismember",sismemberCommand,3,"rF",0,NULL,1,1,1,0,0},
    {"scard",scardCommand,2,"rF",0,NULL,1,1,1,0,0},
    {"spop",spopCommand,2,"wRsF",0,NULL,1,1,1,0,0},
    {"srandmember",srandmemberCommand,-2,"rR",0,NULL,1,1,1,0,0},
    {"sinter",sinterCommand,-2,"rS",0,NULL,1,-1,1,0,0},
    {"sinterstore",sinterstoreCommand,-3,"wm",0,NULL,1,-1,1,0,0},
    {"sunion",sunionCommand,-2,"rS",0,NULL,1,-1,1,0,0},
    {"sunionstore",sunionstoreCommand,-3,"wm",0,NULL,1,-1,1,0,0},
    {"sdiff",sdiffCommand,-2,"rS",0,NULL,1,-1,1,0,0},
    {"sdiffstore",sdiffstoreCommand,-3,"wm",0,NULL,1,-1,1,0,0},
    {"smembers",sinterCommand,2,"rS",0,NULL,1,1,1,0,0},
    {"sscan",sscanCommand,-3,"rR",0,NULL,1,1,1,0,0},
    {"zadd",zaddCommand,-4,"wmF",0,NULL,1,1,1,0,0},
    {"zincrby",zincrbyCommand,4,"wmF",0,NULL,1,1,1,0,0},
    {"zrem",zremCommand,-3,"wF",0,NULL,1,1,1,0,0},
    {"zremrangebyscore",zremrangebyscoreCommand,4,"w",0,NULL,1,1,1,0,0},
    {"zremrangebyrank",zremrangebyrankCommand,4,"w",0,NULL,1,1,1,0,0},
    {"zremrangebylex",zremrangebylexCommand,4,"w",0,NULL,1,1,1,0,0},
    {"zunionstore",zunionstoreCommand,-4,"wm",0,zunionInterGetKeys,0,0,0,0,0},
    {"zinterstore",zinterstoreCommand,-4,"wm",0,zunionInterGetKeys,0,0,0,0,0},
    {"zrange",zrangeCommand,-4,"r",0,NULL,1,1,1,0,0},
    {"zrangebyscore",zrangebyscoreCommand,-4,"r",0,NULL,1,1,1,0,0},
    {"zrevrangebyscore",zrevrangebyscoreCommand,-4,"r",0,NULL,1,1,1,0,0},
    {"zrangebylex",zrangebylexCommand,-4,"r",0,NULL,1,1,1,0,0},
    {"zrevrangebylex",zrevrangebylexCommand,-4,"r",0,NULL,1,1,1,0,0},
    {"zcount",zcountCommand,4,"rF",0,NULL,1,1,1,0,0},
    {"zlexcount",zlexcountCommand,4,"rF",0,NULL,1,1,1,0,0},
    {"zrevrange",zrevrangeCommand,-4,"r",0,NULL,1,1,1,0,0},
    {"zcard",zcardCommand,2,"rF",0,NULL,1,1,1,0,0},
    {"zscore",zscoreCommand,3,"rF",0,NULL,1,1,1,0,0},
    {"zrank",zrankCommand,3,"rF",0,NULL,1,1,1,0,0},
    {"zrevrank",zrevrankCommand,3,"rF",0,NULL,1,1,1,0,0},
    {"zscan",zscanCommand,-3,"rR",0,NULL,1,1,1,0,0},
    {"hset",hsetCommand,4,"wmF",0,NULL,1,1,1,0,0},
    {"hsetnx",hsetnxCommand,4,"wmF",0,NULL,1,1,1,0,0},
    {"hget",hgetCommand,3,"rF",0,NULL,1,1,1,0,0},
    {"hmset",hmsetCommand,-4,"wm",0,NULL,1,1,1,0,0},
    {"hmget",hmgetCommand,-3,"r",0,NULL,1,1,1,0,0},
    {"hincrby",hincrbyCommand,4,"wmF",0,NULL,1,1,1,0,0},
    {"hincrbyfloat",hincrbyfloatCommand,4,"wmF",0,NULL,1,1,1,0,0},
    {"hdel",hdelCommand,-3,"wF",0,NULL,1,1,1,0,0},
    {"hlen",hlenCommand,2,"rF",0,NULL,1,1,1,0,0},
    {"hkeys",hkeysCommand,2,"rS",0,NULL,1,1,1,0,0},
    {"hvals",hvalsCommand,2,"rS",0,NULL,1,1,1,0,0},
    {"hgetall",hgetallCommand,2,"r",0,NULL,1,1,1,0,0},
    {"hexists",hexistsCommand,3,"rF",0,NULL,1,1,1,0,0},
    {"hscan",hscanCommand,-3,"rR",0,NULL,1,1,1,0,0},
    {"incrby",incrbyCommand,3,"wmF",0,NULL,1,1,1,0,0},
    {"decrby",decrbyCommand,3,"wmF",0,NULL,1,1,1,0,0},
    {"incrbyfloat",incrbyfloatCommand,3,"wmF",0,NULL,1,1,1,0,0},
    {"getset",getsetCommand,3,"wm",0,NULL,1,1,1,0,0},
    {"mset",msetCommand,-3,"wm",0,NULL,1,-1,2,0,0},
    {"msetnx",msetnxCommand,-3,"wm",0,NULL,1,-1,2,0,0},
    {"randomkey",randomkeyCommand,1,"rR",0,NULL,0,0,0,0,0},
    {"select",selectCommand,2,"rlF",0,NULL,0,0,0,0,0},
    {"move",moveCommand,3,"wF",0,NULL,1,1,1,0,0},
    {"rename",renameCommand,3,"w",0,NULL,1,2,1,0,0},
    {"renamenx",renamenxCommand,3,"wF",0,NULL,1,2,1,0,0},
    {"expire",expireCommand,3,"wF",0,NULL,1,1,1,0,0},
    {"expireat",expireatCommand,3,"wF",0,NULL,1,1,1,0,0},
    {"pexpire",pexpireCommand,3,"wF",0,NULL,1,1,1,0,0},
    {"pexpireat",pexpireatCommand,3,"wF",0,NULL,1,1,1,0,0},
    {"keys",keysCommand,2,"rS",0,NULL,0,0,0,0,0},
    {"scan",scanCommand,-2,"rR",0,NULL,0,0,0,0,0},
    {"dbsize",dbsizeCommand,1,"rF",0,NULL,0,0,0,0,0},
    {"auth",authCommand,2,"rsltF",0,NULL,0,0,0,0,0},
    {"ping",pingCommand,-1,"rtF",0,NULL,0,0,0,0,0},
    {"echo",echoCommand,2,"rF",0,NULL,0,0,0,0,0},
    {"save",saveCommand,1,"ars",0,NULL,0,0,0,0,0},
    {"bgsave",bgsaveCommand,1,"ar",0,NULL,0,0,0,0,0},
    {"bgrewriteaof",bgrewriteaofCommand,1,"ar",0,NULL,0,0,0,0,0},
    {"shutdown",shutdownCommand,-1,"arlt",0,NULL,0,0,0,0,0},
    {"lastsave",lastsaveCommand,1,"rRF",0,NULL,0,0,0,0,0},
    {"type",typeCommand,2,"rF",0,NULL,1,1,1,0,0},
    {"multi",multiCommand,1,"rsF",0,NULL,0,0,0,0,0},
    {"exec",execCommand,1,"sM",0,NULL,0,0,0,0,0},
    {"discard",discardCommand,1,"rsF",0,NULL,0,0,0,0,0},
    {"sync",syncCommand,1,"ars",0,NULL,0,0,0,0,0},
    {"psync",syncCommand,3,"ars",0,NULL,0,0,0,0,0},
    {"replconf",replconfCommand,-1,"arslt",0,NULL,0,0,0,0,0},
    {"flushdb",flushdbCommand,1,"w",0,NULL,0,0,0,0,0},
    {"flushall",flushallCommand,1,"w",0,NULL,0,0,0,0,0},
    {"sort",sortCommand,-2,"wm",0,sortGetKeys,1,1,1,0,0},
    {"info",infoCommand,-1,"rlt",0,NULL,0,0,0,0,0},
    {"monitor",monitorCommand,1,"ars",0,NULL,0,0,0,0,0},
    {"ttl",ttlCommand,2,"rF",0,NULL,1,1,1,0,0},
    {"pttl",pttlCommand,2,"rF",0,NULL,1,1,1,0,0},
    {"persist",persistCommand,2,"wF",0,NULL,1,1,1,0,0},
    {"slaveof",slaveofCommand,3,"ast",0,NULL,0,0,0,0,0},
    {"role",roleCommand,1,"lst",0,NULL,0,0,0,0,0},
    {"debug",debugCommand,-2,"as",0,NULL,0,0,0,0,0},
    {"config",configCommand,-2,"art",0,NULL,0,0,0,0,0},
    {"subscribe",subscribeCommand,-2,"rpslt",0,NULL,0,0,0,0,0},
    {"unsubscribe",unsubscribeCommand,-1,"rpslt",0,NULL,0,0,0,0,0},
    {"psubscribe",psubscribeCommand,-2,"rpslt",0,NULL,0,0,0,0,0},
    {"punsubscribe",punsubscribeCommand,-1,"rpslt",0,NULL,0,0,0,0,0},
    {"publish",publishCommand,3,"pltrF",0,NULL,0,0,0,0,0},
    {"pubsub",pubsubCommand,-2,"pltrR",0,NULL,0,0,0,0,0},
    {"watch",watchCommand,-2,"rsF",0,NULL,1,-1,1,0,0},
    {"unwatch",unwatchCommand,1,"rsF",0,NULL,0,0,0,0,0},
    {"cluster",clusterCommand,-2,"ar",0,NULL,0,0,0,0,0},
    {"restore",restoreCommand,-4,"wm",0,NULL,1,1,1,0,0},
    {"restore-asking",restoreCommand,-4,"wmk",0,NULL,1,1,1,0,0},
    {"migrate",migrateCommand,-6,"w",0,NULL,0,0,0,0,0},
    {"asking",askingCommand,1,"r",0,NULL,0,0,0,0,0},
    {"readonly",readonlyCommand,1,"rF",0,NULL,0,0,0,0,0},
    {"readwrite",readwriteCommand,1,"rF",0,NULL,0,0,0,0,0},
    {"dump",dumpCommand,2,"r",0,NULL,1,1,1,0,0},
    {"object",objectCommand,3,"r",0,NULL,2,2,2,0,0},
    {"client",clientCommand,-2,"rs",0,NULL,0,0,0,0,0},
    {"eval",evalCommand,-3,"s",0,evalGetKeys,0,0,0,0,0},
    {"evalsha",evalShaCommand,-3,"s",0,evalGetKeys,0,0,0,0,0},
    {"slowlog",slowlogCommand,-2,"r",0,NULL,0,0,0,0,0},
    {"script",scriptCommand,-2,"rs",0,NULL,0,0,0,0,0},
    {"time",timeCommand,1,"rRF",0,NULL,0,0,0,0,0},
    {"bitop",bitopCommand,-4,"wm",0,NULL,2,-1,1,0,0},
    {"bitcount",bitcountCommand,-2,"r",0,NULL,1,1,1,0,0},
    {"bitpos",bitposCommand,-3,"r",0,NULL,1,1,1,0,0},
    {"wait",waitCommand,3,"rs",0,NULL,0,0,0,0,0},
    {"command",commandCommand,0,"rlt",0,NULL,0,0,0,0,0},
    {"pfselftest",pfselftestCommand,1,"r",0,NULL,0,0,0,0,0},
    {"pfadd",pfaddCommand,-2,"wmF",0,NULL,1,1,1,0,0},
    {"pfcount",pfcountCommand,-2,"r",0,NULL,1,1,1,0,0},
    {"pfmerge",pfmergeCommand,-2,"wm",0,NULL,1,-1,1,0,0},
    {"pfdebug",pfdebugCommand,-3,"w",0,NULL,0,0,0,0,0},
    {"latency",latencyCommand,-2,"arslt",0,NULL,0,0,0,0,0}
};

     记录两点知识：1、redis实现了命令行命令库，支持多种操作。2、redis有两种持久化模式AOF和RDB，前者保存数据快照，后者记录操作命令

      在此章节中我们主要来看看redis服务器的启动过程

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

    /* We need to initialize our libraries, and the server configuration. */
	//如果定义了可修改进程名称的函数则调用函数
#ifdef INIT_SETPROCTITLE_REPLACEMENT
    spt_init(argc, argv);
#endif
	//设置locale
    setlocale(LC_COLLATE,"");
	//确定线程安全
    zmalloc_enable_thread_safeness();
	//设置内存溢出handler
    zmalloc_set_oom_handler(redisOutOfMemoryHandler);
    srand(time(NULL)^getpid());
	//获取当前时间
    gettimeofday(&tv,NULL);
    dictSetHashFunctionSeed(tv.tv_sec^tv.tv_usec^getpid());
    server.sentinel_mode = checkForSentinelMode(argc,argv);
    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. */
    if (server.sentinel_mode) {
        initSentinelConfig();
        initSentinel();
    }

    if (argc >= 2) {
		//解析输入参数的索引
        int j = 1; /* First option to parse in argv[] */
		//创建一个只包含空白字符串的sds（动态字符串）
        sds options = sdsempty();
		//server的配置文件指针
        char *configfile = NULL;

        /* Handle special options --help and --version */
		//如果输入参数有-v或--version或--help或-h或--test-memory之类的参数
        if (strcmp(argv[1], "-v") == 0 ||
            strcmp(argv[1], "--version") == 0) version();//返回redis版本
        if (strcmp(argv[1], "--help") == 0 ||
            strcmp(argv[1], "-h") == 0) usage();//返回帮助
        if (strcmp(argv[1], "--test-memory") == 0) {
			//如果参数有三个则获取最后一个参数并检测内存大小后直接退出
            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? */
		//从第二个参数的第一个开始（第一个是命令）如果第一个或第二个参数不是‘-’
        if (argv[j][0] != '-' || argv[j][1] != '-')
			//配置文件即是当前参数
            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. */
		//j的范围不能超出参数个数一直循环处理
        while(j != argc) {
			//从第二个参数的第一个开始（第一个是命令）如果第一个或第二个参数不是‘-’
            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++;
        }
		//如果是该服务器是Sentinel实例（Redis Sentinel是一个分布式系统用于管理多个Redis服务器）
		//且存在配置文件指针，它的内容是'-'则发出警告并退出系统，也就是Sentinel实例必须有配置文件
        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);
        }
		//如果存在配置文件则获取配置文件
        if (configfile) server.configfile = getAbsolutePath(configfile);
		//清空原有服务器配置
        resetServerSaveParams();
        //加载新的服务器配置参数
		loadServerConfig(configfile,options);
		//清空保存用户输入参数的options字符串
        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");
    }
	//如果服务器配置成以守护进程模式运行则执行相关操作
    if (server.daemonize) daemonize();
	//初始化服务器，包括初始化进程号当前客户端等各项参数
    initServer();
    //如果是守护进程模式的服务器实例则创建PidFile记录进程信息
	if (server.daemonize) createPidFile();
    //设置进程标题，形如：xx(命令行第一个参数) xx(服务器绑定的地址数):xx（服务器端口）xx(服务器模式)
	redisSetProcTitle(argv[0]);
    //打印 ASCII LOGO
	redisAsciiArt();

    if (!server.sentinel_mode) {
        /* Things not needed when running in Sentinel mode. */
        redisLog(REDIS_WARNING,"Server started, Redis version " REDIS_VERSION);
    #ifdef __linux__
        linuxMemoryWarnings();
    #endif
		//检查服务器tcp操作的记录文件
        checkTcpBacklogSettings();
        //从AOF文件或RDB文件中还原数据库（AOF和RDB是redis的
		//两种持久化方式，前者生成数据快照，后者记录操作命令）
		loadDataFromDisk();
        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 {
        sentinelIsRunning();
    }

    /* 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);
    }
    aeSetBeforeSleepProc(server.el,beforeSleep);
	//开始事件循环机制
    aeMain(server.el);
	//服务器关闭停止事件循环
    aeDeleteEventLoop(server.el);
    return 0;
}