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;
}
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