Redis服务器的处理流程：
一个命令请求从发送到获得回复的过程中，如果我们执行下面命令:
redis > set KEY VALUE
OK
其中的操作有：
1）客户端向服务器发送命令请求
2）服务起接收并处理客户端发送来的命令请求，在数据库中进行设置操作，并产生命令回复OK
3）服务器将命令回复OK发送给客户端
4）客户端显示内容打印给用户看
接下来详细介绍第2步的操作
服务器读取套接字中的命令请求，并把内容保存到客户端状态的输入缓冲区中，也就是redisServer/clients，对输入缓冲区的命令请求进行分析 ，提取出命令请求中包含的命令参数，以及命令参数的个数，然后分别将参数和参数个数保存到clients中 （argv,argc）;当套接字读事件时， 调用命令执行器，执行客户端的命令
之后，分析程序将对输入缓冲区中的协议进行分析：
*3\r\n$3\r\nSET\r\n$3\r\nKEY\r\n$5\r\nVALUE\r\n
并将得出的分析结构保存到客户端状态的argv属性和argc属性里面，如下图所示:
代码流程跟踪:
redis.c/initServer/aeCreateFileEvent(acceptTcpHandler) -> networking.c/acceptTcpHandler/acceptCommonHandler
-> networking.c/acceptCommonHandler/createClient -> networking.c/createClient/aeCreateFileEvent(readQueryFromClient)
-> networking.c/readQueryFromClient
其中server.ipfd数组大小为16，因为redis默认为16个数据库，所以需要创建16个监听的文件句柄，做epoll轮询
命令参数的解析在networking.c/readQueryFromClient/processInputBuffer，把参数存储到argv和argc中去
当客户端连接建立和参数解析完成之后，命令执行器开始工作，去查找命令的实现，代码在
networking.c/readQueryFromClient/processInputBuffer -> networking.c/processInputBuffer/processCommand
通过里层的lookupCommand方法查看对应的命令函数，通过从redisCommand中取出对应的数据，源码如下：
struct redisCommand redisCommandTable[] = {
{"get",getCommand,2,"rF",0,NULL,1,1,1,0,0},
{"set",setCommand,-3,"wm",0,NULL,1,1,1,0,0},
{"setnx",setnxCommand,3,"wmF",0,NULL,1,1,1,0,0},
{"setex",setexCommand,4,"wm",0,NULL,1,1,1,0,0},
{"psetex",psetexCommand,4,"wm",0,NULL,1,1,1,0,0},
{"append",appendCommand,3,"wm",0,NULL,1,1,1,0,0},
{"strlen",strlenCommand,2,"rF",0,NULL,1,1,1,0,0},
{"del",delCommand,-2,"w",0,NULL,1,-1,1,0,0},
{"exists",existsCommand,-2,"rF",0,NULL,1,-1,1,0,0},
{"setbit",setbitCommand,4,"wm",0,NULL,1,1,1,0,0},
{"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,migrateGetKeys,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}
};
当所有的属性都解析完毕之后，开始调用函数指针方法，方法为:
redis.c中
/* Call() is the core of Redis execution of a command */
void call(redisClient *c, int flags);
类似执行client->cmd->proc(client);
方法执行完成之后，命令回复保存到客户端的输出缓冲区中，由于是set命令，为固定大小缓冲区，
//固定大小缓冲区
char buf[];
int bufpos;
//可变大小缓冲区
list *reply;
执行之后的后续操作，比如开启了慢日志查询，那么会判断是否需要记录日志，也是在call方法中执行的：
/* Log the command into the Slow log if needed, and populate the
* per-command statistics that we show in INFO commandstats. */
if (flags & REDIS_CALL_SLOWLOG && c->cmd->proc != execCommand) {
char *latency_event = (c->cmd->flags & REDIS_CMD_FAST) ?
"fast-command" : "command";
latencyAddSampleIfNeeded(latency_event,duration/1000);
slowlogPushEntryIfNeeded(c->argv,c->argc,duration);
}
如果开启了AOF持久化功能，如果其他从服务器正在复制当前这个服务器，这个命令会被传播给其他从服务器
/* Propagate the command into the AOF and replication link */
if (flags & REDIS_CALL_PROPAGATE) {
int flags = REDIS_PROPAGATE_NONE;
if (c->flags & REDIS_FORCE_REPL) flags |= REDIS_PROPAGATE_REPL;
if (c->flags & REDIS_FORCE_AOF) flags |= REDIS_PROPAGATE_AOF;
if (dirty)
flags |= (REDIS_PROPAGATE_REPL | REDIS_PROPAGATE_AOF);
if (flags != REDIS_PROPAGATE_NONE)
propagate(c->cmd,c->db->id,c->argv,c->argc,flags);
}
/* Restore the old FORCE_AOF/REPL flags, since call can be executed
* recursively. */
c->flags &= ~(REDIS_FORCE_AOF|REDIS_FORCE_REPL);
c->flags |= client_old_flags & (REDIS_FORCE_AOF|REDIS_FORCE_REPL);
/* Handle the alsoPropagate() API to handle commands that want to propagate
* multiple separated commands. */
if (server.also_propagate.numops) {
int j;
redisOp *rop;
for (j = 0; j < server.also_propagate.numops; j++) {
rop = &server.also_propagate.ops[j];
propagate(rop->cmd, rop->dbid, rop->argv, rop->argc, rop->target);
}
redisOpArrayFree(&server.also_propagate);
}
serverCron函数，这个在之前的AOF和RDB操作以及事件中已经说过，它是一种时间事件；更新服务器时间缓存，redis中不少功能 需要获取系统的当前时间，
struct redisServer {
// 保存了秒级精确的系统当前UNIX时间戳
time_t unixtime;
// 保存了毫秒级精确的系统当前UNIX时间戳
long long mstime;
}
/* Update the time cache. */
updateCachedTime();
serverCron函数默认会以100毫秒一次的频率更新unixtime属性和mstime属性，所以他们的精确度不是很高。
LRU时钟，服务器状态中的lrulock属性保存了服务器的LRU时钟，这个属性和上面介绍的unixtime属性、mstime属性一样，都是服务器缓存中的一种：
struct redisServer {
// key的空转时间，默认10s更新一次时钟缓存
unsigned lrulock:22;
}
每个redis对象都有一个lru属性，这个lru属性保存了对象最后一次被命令访问的时间
struct redisObject {
unsigned lru:22;
}
当服务器要计算一个key的空转时间，程序会用服务器的lrulock属性记录的时间戳减去对象的lru属性记录的时间，得出的计算结果就是这个对象的空转时间
再就是更新服务器每秒执行命令次数，这是一种数据采样
管理客户端资源，serverCron函数每次会执行clientsCron函数，主要处理超时的客户端以及关闭超出输出缓冲区的客户端
管理数据库资源、持久化操作等等