概述
这篇文章的目的是为了描述redis server在处理client命令的执行过程，大概包括流程图、源码、以及redis的命令格式说明，redis的通信协议参考自redis的官网。
命令执行过程
整个redis的server端命令执行过程就如下面这个流程图：
- nio层读取数据
- 解析数据到命令行格式
- 查找命令对应的执行函数执行命令
- 同步数据到slave和aof
redis.png
命令执行过程源码
读取命令
nread = read(fd, c->querybuf+qblen, readlen);负责读取命令数，通过processInputBuffer进行下一步处理。
void readQueryFromClient(aeEventLoop *el, int fd, void *privdata, int mask) {
redisClient *c = (redisClient*) privdata;
int nread, readlen;
size_t qblen;
REDIS_NOTUSED(el);
REDIS_NOTUSED(mask);
// 设置服务器的当前客户端
server.current_client = c;
// 读入长度（默认为 16 MB）
readlen = REDIS_IOBUF_LEN;
// 获取查询缓冲区当前内容的长度
// 如果读取出现 short read ，那么可能会有内容滞留在读取缓冲区里面
// 这些滞留内容也许不能完整构成一个符合协议的命令，
qblen = sdslen(c->querybuf);
// 如果有需要，更新缓冲区内容长度的峰值（peak）
if (c->querybuf_peak < qblen) c->querybuf_peak = qblen;
// 为查询缓冲区分配空间
c->querybuf = sdsMakeRoomFor(c->querybuf, readlen);
// 读入内容到查询缓存
nread = read(fd, c->querybuf+qblen, readlen);
if (nread) {
// 根据内容，更新查询缓冲区（SDS） free 和 len 属性
// 并将 '\0' 正确地放到内容的最后
sdsIncrLen(c->querybuf,nread);
// 记录服务器和客户端最后一次互动的时间
c->lastinteraction = server.unixtime;
// 如果客户端是 master 的话，更新它的复制偏移量
if (c->flags & REDIS_MASTER) c->reploff += nread;
}
// 查询缓冲区长度超出服务器最大缓冲区长度
// 清空缓冲区并释放客户端
if (sdslen(c->querybuf) > server.client_max_querybuf_len) {
sds ci = catClientInfoString(sdsempty(),c), bytes = sdsempty();
bytes = sdscatrepr(bytes,c->querybuf,64);
redisLog(REDIS_WARNING,"Closing client that reached max query buffer length: %s (qbuf initial bytes: %s)", ci, bytes);
sdsfree(ci);
sdsfree(bytes);
freeClient(c);
return;
}
// 从查询缓存重读取内容，创建参数，并执行命令
// 函数会执行到缓存中的所有内容都被处理完为止
processInputBuffer(c);
server.current_client = NULL;
}
解析命令
核心在于processInlineBuffer处理内联命令，processMultibulkBuffer处理批量命令包括get/set等，核心的processCommand用于执行命令。
// 处理客户端输入的命令内容
void processInputBuffer(redisClient *c) {
while(sdslen(c->querybuf)) {
// 判断请求的类型
// 两种类型的区别可以在 Redis 的通讯协议上查到：
// http://redis.readthedocs.org/en/latest/topic/protocol.html
// 简单来说，多条查询是一般客户端发送来的，
// 而内联查询则是 TELNET 发送来的
if (!c->reqtype) {
if (c->querybuf[0] == '*') {
// 多条查询
c->reqtype = REDIS_REQ_MULTIBULK;
} else {
// 内联查询
c->reqtype = REDIS_REQ_INLINE;
}
}
// 将缓冲区中的内容转换成命令，以及命令参数
if (c->reqtype == REDIS_REQ_INLINE) {
if (processInlineBuffer(c) != REDIS_OK) break;
} else if (c->reqtype == REDIS_REQ_MULTIBULK) {
if (processMultibulkBuffer(c) != REDIS_OK) break;
} else {
redisPanic("Unknown request type");
}
/* Multibulk processing could see a <= 0 length. */
if (c->argc == 0) {
resetClient(c);
} else {
/* Only reset the client when the command was executed. */
// 执行命令，并重置客户端
if (processCommand(c) == REDIS_OK)
resetClient(c);
}
}
}
执行命令前准备
执行命令的过程其实主要是寻找命令对应的执行函数，通过lookupCommand查找对应的执行命令，通过call执行命令。
int processCommand(redisClient *c) {
// 特别处理 quit 命令
if (!strcasecmp(c->argv[0]->ptr,"quit")) {
addReply(c,shared.ok);
c->flags |= REDIS_CLOSE_AFTER_REPLY;
return REDIS_ERR;
}
// 查找命令，并进行命令合法性检查，以及命令参数个数检查
c->cmd = c->lastcmd = lookupCommand(c->argv[0]->ptr);
// 中间省略了很多异常情况的检测，包括是否超过内存限制、是否合法命令等
if (c->flags & REDIS_MULTI &&
c->cmd->proc != execCommand && c->cmd->proc != discardCommand &&
c->cmd->proc != multiCommand && c->cmd->proc != watchCommand)
{
// 在事务上下文中
// 除 EXEC 、 DISCARD 、 MULTI 和 WATCH 命令之外
// 其他所有命令都会被入队到事务队列中
queueMultiCommand(c);
addReply(c,shared.queued);
} else {
// 执行命令
call(c,REDIS_CALL_FULL);
c->woff = server.master_repl_offset;
// 处理那些解除了阻塞的键
if (listLength(server.ready_keys))
handleClientsBlockedOnLists();
}
return REDIS_OK;
}
执行命令
负责执行命令c->cmd->proc并更新统计信息，执行完成后负责同步数据propagate。
// 调用命令的实现函数，执行命令
void call(redisClient *c, int flags) {
// 执行实现函数
c->cmd->proc(c);
// 将命令复制到 AOF 和 slave 节点
if (flags & REDIS_CALL_PROPAGATE) {
int flags = REDIS_PROPAGATE_NONE;
// 强制 REPL 传播
if (c->flags & REDIS_FORCE_REPL) flags |= REDIS_PROPAGATE_REPL;
// 强制 AOF 传播
if (c->flags & REDIS_FORCE_AOF) flags |= REDIS_PROPAGATE_AOF;
// 如果数据库有被修改，那么启用 REPL 和 AOF 传播
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);
}
同步执行命令
主要是负责同步数据到AOF文件和slave节点，feedAppendOnlyFile负责同步到AOF文件，replicationFeedSlaves负责同步
/* Propagate the specified command (in the context of the specified database id)
* to AOF and Slaves.
*
* 将指定命令（以及执行该命令的上下文，比如数据库 id 等信息）传播到 AOF 和 slave 。
*
* flags are an xor between:
* FLAG 可以是以下标识的 xor ：
*
* + REDIS_PROPAGATE_NONE (no propagation of command at all)
* 不传播
*
* + REDIS_PROPAGATE_AOF (propagate into the AOF file if is enabled)
* 传播到 AOF
*
* + REDIS_PROPAGATE_REPL (propagate into the replication link)
* 传播到 slave
*/
void propagate(struct redisCommand *cmd, int dbid, robj **argv, int argc,
int flags)
{
// 传播到 AOF
if (server.aof_state != REDIS_AOF_OFF && flags & REDIS_PROPAGATE_AOF)
feedAppendOnlyFile(cmd,dbid,argv,argc);
// 传播到 slave
if (flags & REDIS_PROPAGATE_REPL)
replicationFeedSlaves(server.slaves,dbid,argv,argc);
}
同步AOF
AOF涉及的缓存有多份，包括
- 首先先缓存在局部的buf当中
- 然后将局部buf的数据拷贝到全局server.aof_buf当中
- 如果现在刚好在重写AOF文件，那么还会将数据拷贝到重写缓存当中。
/*
* 将命令追加到 AOF 文件中，
* 如果 AOF 重写正在进行，那么也将命令追加到 AOF 重写缓存中。
*/
void feedAppendOnlyFile(struct redisCommand *cmd, int dictid, robj **argv, int argc) {
sds buf = sdsempty();
robj *tmpargv[3];
/*
* 使用 SELECT 命令，显式设置数据库，确保之后的命令被设置到正确的数据库
*/
if (dictid != server.aof_selected_db) {
char seldb[64];
snprintf(seldb,sizeof(seldb),"%d",dictid);
buf = sdscatprintf(buf,"*2\r\n$6\r\nSELECT\r\n$%lu\r\n%s\r\n",
(unsigned long)strlen(seldb),seldb);
server.aof_selected_db = dictid;
}
// EXPIRE 、 PEXPIRE 和 EXPIREAT 命令
if (cmd->proc == expireCommand || cmd->proc == pexpireCommand ||
cmd->proc == expireatCommand) {
/*
* 将 EXPIRE 、 PEXPIRE 和 EXPIREAT 都翻译成 PEXPIREAT
*/
buf = catAppendOnlyExpireAtCommand(buf,cmd,argv[1],argv[2]);
// SETEX 和 PSETEX 命令
} else if (cmd->proc == setexCommand || cmd->proc == psetexCommand) {
/* Translate SETEX/PSETEX to SET and PEXPIREAT
*
* 将两个命令都翻译成 SET 和 PEXPIREAT
*/
// SET
tmpargv[0] = createStringObject("SET",3);
tmpargv[1] = argv[1];
tmpargv[2] = argv[3];
buf = catAppendOnlyGenericCommand(buf,3,tmpargv);
// PEXPIREAT
decrRefCount(tmpargv[0]);
buf = catAppendOnlyExpireAtCommand(buf,cmd,argv[1],argv[2]);
// 其他命令
} else {
buf = catAppendOnlyGenericCommand(buf,argc,argv);
}
/*
* 将命令追加到 AOF 缓存中，
* 在重新进入事件循环之前，这些命令会被冲洗到磁盘上，
* 并向客户端返回一个回复。
*/
if (server.aof_state == REDIS_AOF_ON)
server.aof_buf = sdscatlen(server.aof_buf,buf,sdslen(buf));
/*
* 如果 BGREWRITEAOF 正在进行，
* 那么我们还需要将命令追加到重写缓存中，
* 从而记录当前正在重写的 AOF 文件和数据库当前状态的差异。
*/
if (server.aof_child_pid != -1)
aofRewriteBufferAppend((unsigned char*)buf,sdslen(buf));
// 释放
sdsfree(buf);
}
命令行映射关系表
包含了命令和对应执行函数的映射关系，应该看上去很清晰命令。
struct redisCommand redisCommandTable[] = {
{"get",getCommand,2,"r",0,NULL,1,1,1,0,0},
{"set",setCommand,-3,"wm",0,NULL,1,1,1,0,0},
{"setnx",setnxCommand,3,"wm",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,"r",0,NULL,1,1,1,0,0},
{"del",delCommand,-2,"w",0,NULL,1,-1,1,0,0},
{"exists",existsCommand,2,"r",0,NULL,1,1,1,0,0},
{"setbit",setbitCommand,4,"wm",0,NULL,1,1,1,0,0},
{"getbit",getbitCommand,3,"r",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,"wm",0,NULL,1,1,1,0,0},
{"decr",decrCommand,2,"wm",0,NULL,1,1,1,0,0},
{"mget",mgetCommand,-2,"r",0,NULL,1,-1,1,0,0},
{"rpush",rpushCommand,-3,"wm",0,NULL,1,1,1,0,0},
{"lpush",lpushCommand,-3,"wm",0,NULL,1,1,1,0,0},
{"rpushx",rpushxCommand,3,"wm",0,NULL,1,1,1,0,0},
{"lpushx",lpushxCommand,3,"wm",0,NULL,1,1,1,0,0},
{"linsert",linsertCommand,5,"wm",0,NULL,1,1,1,0,0},
{"rpop",rpopCommand,2,"w",0,NULL,1,1,1,0,0},
{"lpop",lpopCommand,2,"w",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,"r",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,"wm",0,NULL,1,1,1,0,0},
{"srem",sremCommand,-3,"w",0,NULL,1,1,1,0,0},
{"smove",smoveCommand,4,"w",0,NULL,1,2,1,0,0},
{"sismember",sismemberCommand,3,"r",0,NULL,1,1,1,0,0},
{"scard",scardCommand,2,"r",0,NULL,1,1,1,0,0},
{"spop",spopCommand,2,"wRs",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,"wm",0,NULL,1,1,1,0,0},
{"zincrby",zincrbyCommand,4,"wm",0,NULL,1,1,1,0,0},
{"zrem",zremCommand,-3,"w",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,"r",0,NULL,1,1,1,0,0},
{"zlexcount",zlexcountCommand,4,"r",0,NULL,1,1,1,0,0},
{"zrevrange",zrevrangeCommand,-4,"r",0,NULL,1,1,1,0,0},
{"zcard",zcardCommand,2,"r",0,NULL,1,1,1,0,0},
{"zscore",zscoreCommand,3,"r",0,NULL,1,1,1,0,0},
{"zrank",zrankCommand,3,"r",0,NULL,1,1,1,0,0},
{"zrevrank",zrevrankCommand,3,"r",0,NULL,1,1,1,0,0},
{"zscan",zscanCommand,-3,"rR",0,NULL,1,1,1,0,0},
{"hset",hsetCommand,4,"wm",0,NULL,1,1,1,0,0},
{"hsetnx",hsetnxCommand,4,"wm",0,NULL,1,1,1,0,0},
{"hget",hgetCommand,3,"r",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,"wm",0,NULL,1,1,1,0,0},
{"hincrbyfloat",hincrbyfloatCommand,4,"wm",0,NULL,1,1,1,0,0},
{"hdel",hdelCommand,-3,"w",0,NULL,1,1,1,0,0},
{"hlen",hlenCommand,2,"r",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,"r",0,NULL,1,1,1,0,0},
{"hscan",hscanCommand,-3,"rR",0,NULL,1,1,1,0,0},
{"incrby",incrbyCommand,3,"wm",0,NULL,1,1,1,0,0},
{"decrby",decrbyCommand,3,"wm",0,NULL,1,1,1,0,0},
{"incrbyfloat",incrbyfloatCommand,3,"wm",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,"rl",0,NULL,0,0,0,0,0},
{"move",moveCommand,3,"w",0,NULL,1,1,1,0,0},
{"rename",renameCommand,3,"w",0,NULL,1,2,1,0,0},
{"renamenx",renamenxCommand,3,"w",0,NULL,1,2,1,0,0},
{"expire",expireCommand,3,"w",0,NULL,1,1,1,0,0},
{"expireat",expireatCommand,3,"w",0,NULL,1,1,1,0,0},
{"pexpire",pexpireCommand,3,"w",0,NULL,1,1,1,0,0},
{"pexpireat",pexpireatCommand,3,"w",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,"r",0,NULL,0,0,0,0,0},
{"auth",authCommand,2,"rslt",0,NULL,0,0,0,0,0},
{"ping",pingCommand,1,"rt",0,NULL,0,0,0,0,0},
{"echo",echoCommand,2,"r",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,"rR",0,NULL,0,0,0,0,0},
{"type",typeCommand,2,"r",0,NULL,1,1,1,0,0},
{"multi",multiCommand,1,"rs",0,NULL,0,0,0,0,0},
{"exec",execCommand,1,"sM",0,NULL,0,0,0,0,0},
{"discard",discardCommand,1,"rs",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,"r",0,NULL,1,1,1,0,0},
{"pttl",pttlCommand,2,"r",0,NULL,1,1,1,0,0},
{"persist",persistCommand,2,"w",0,NULL,1,1,1,0,0},
{"slaveof",slaveofCommand,3,"ast",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,"pltr",0,NULL,0,0,0,0,0},
{"pubsub",pubsubCommand,-2,"pltrR",0,NULL,0,0,0,0,0},
{"watch",watchCommand,-2,"rs",0,NULL,1,-1,1,0,0},
{"unwatch",unwatchCommand,1,"rs",0,NULL,0,0,0,0,0},
{"cluster",clusterCommand,-2,"ar",0,NULL,0,0,0,0,0},
{"restore",restoreCommand,-4,"awm",0,NULL,1,1,1,0,0},
{"restore-asking",restoreCommand,-4,"awmk",0,NULL,1,1,1,0,0},
{"migrate",migrateCommand,-6,"aw",0,NULL,0,0,0,0,0},
{"asking",askingCommand,1,"r",0,NULL,0,0,0,0,0},
{"readonly",readonlyCommand,1,"r",0,NULL,0,0,0,0,0},
{"readwrite",readwriteCommand,1,"r",0,NULL,0,0,0,0,0},
{"dump",dumpCommand,2,"ar",0,NULL,1,1,1,0,0},
{"object",objectCommand,-2,"r",0,NULL,2,2,2,0,0},
{"client",clientCommand,-2,"ar",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,"ras",0,NULL,0,0,0,0,0},
{"time",timeCommand,1,"rR",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},
{"pfselftest",pfselftestCommand,1,"r",0,NULL,0,0,0,0,0},
{"pfadd",pfaddCommand,-2,"wm",0,NULL,1,1,1,0,0},
{"pfcount",pfcountCommand,-2,"w",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}
};
redis 通信协议
新版统一请求协议
协议的一般格式如下，注意前面的*或者$等字符，结尾的\r\n是分隔符。
-----------------------------------------
格式如下：
---------------------------------------------
*<参数数量> CR LF
$<参数 1 的字节数量> CR LF
<参数 1 的数据> CR LF
...
$<参数 N 的字节数量> CR LF
<参数 N 的数据> CR LF
-----------------------------------------
协议请求例子如下：
-----------------------------------------
*3
$3
SET
$5
mykey
$7
myvalue
-----------------------------------------
实际传输格式如下：
-----------------------------------------
"*3\r\n$3\r\nSET\r\n$5\r\nmykey\r\n$7\r\nmyvalue\r\n"
-----------------------------------------
响应报文格式如下：
-----------------------------------------
状态回复（status reply）的第一个字节是 "+"
错误回复（error reply）的第一个字节是 "-"
整数回复（integer reply）的第一个字节是 ":"
批量回复（bulk reply）的第一个字节是 "$"
多条批量回复（multi bulk reply）的第一个字节是 "*"
-----------------------------------------
状态回复报文格式如下：
-----------------------------------------
+OK
-----------------------------------------
错误回复报文格式如下：
-----------------------------------------
-ERR unknown command 'foobar'
-WRONGTYPE Operation against a key holding the wrong kind of value
-----------------------------------------
整数回复报文格式如下：
-----------------------------------------
整数回复就是一个以 ":" 开头， CRLF 结尾的字符串表示的整数。
比如说， ":0\r\n" 和 ":1000\r\n" 都是整数回复。
-----------------------------------------
批量回复报文格式如下：
-----------------------------------------
服务器使用批量回复来返回二进制安全的字符串，字符串的最大长度为 512 MB 。
服务器发送的内容中：
* 第一字节为 `"$"` 符号
* 接下来跟着的是表示实际回复长度的数字值
* 之后跟着一个 CR LF
* 再后面跟着的是实际回复数据
* 最末尾是另一个 CR LF
对于前面的命令，服务器实际发送的内容为：
"$6\r\nfoobar\r\n"
如果被请求的值不存在， 那么批量回复会将特殊值 `-1` 用作回复的长度值， 就像这样：
服务器：$-1
-----------------------------------------
多条批量回复报文格式如下：
-----------------------------------------
像 [LRANGE] 这样的命令需要返回多个值， 这一目标可以通过多条批量回复来完成。
多条批量回复是由多个回复组成的数组， 数组中的每个元素都可以是任意类型的回复， 包括多条批量回复本身。
多条批量回复的第一个字节为 `"*"` ， 后跟一个字符串表示的整数值， 这个值记录了多条批量回复所包含的回复数量， 再后面是一个 CRLF 。
客户端： LRANGE mylist 0 3
服务器： *4
服务器： $3
服务器： foo
服务器： $3
服务器： bar
服务器： $5
服务器： Hello
服务器： $5
服务器： World
在上面的示例中，服务器发送的所有字符串都由 CRLF 结尾。
正如你所见到的那样， 多条批量回复所使用的格式， 和客户端发送命令时使用的统一请求协议的格式一模一样。 它们之间的唯一区别是：
统一请求协议只发送批量回复。
而服务器应答命令时所发送的多条批量回复，则可以包含任意类型的回复。
以下例子展示了一个多条批量回复， 回复中包含四个整数值， 以及一个二进制安全字符串：
*5\r\n
:1\r\n
:2\r\n
:3\r\n
:4\r\n
$6\r\n
foobar\r\n
在回复的第一行， 服务器发送 *5\r\n ， 表示这个多条批量回复包含 5 条回复， 再后面跟着的则是 5 条回复的正文。
多条批量回复也可以是空白的（empty）， 就像这样：
客户端： LRANGE nokey 0 1
服务器： *0\r\n
无内容的多条批量回复（null multi bulk reply）也是存在的，
比如当 [BLPOP]命令的阻塞时间超过最大时限时， 它就返回一个无内容的多条批量回复， 这个回复的计数值为 `-1` ：
客户端： BLPOP key 1
服务器： *-1\r\n
多条批量回复中的元素可以将自身的长度设置为 `-1` ， 从而表示该元素不存在， 并且也不是一个空白字符串（empty string）。
当 [SORT] 命令使用 `GET pattern` 选项对一个不存在的键进行操作时， 就会发生多条批量回复中带有空白元素的情况。
以下例子展示了一个包含空元素的多重批量回复：
服务器： *3
服务器： $3
服务器： foo
服务器： $-1
服务器： $3
服务器： bar
其中， 回复中的第二个元素为空。
内联命令格式
当你需要和 Redis 服务器进行沟通， 但又找不到 redis-cli ，
而手上只有 telnet 的时候， 你可以通过 Redis 特别为这种情形而设的内联命令格式来发送命令。
因为没有了统一请求协议中的 "*" 项来声明参数的数量， 所以在 telnet 会话输入命令的时候，
必须使用空格来分割各个参数， 服务器在接收到数据之后， 会按空格对用户的输入进行分析（parse）， 并获取其中的命令参数。
例子如下：
-----------------------------------------
客户端： PING
服务器： +PONG
