本篇文章为大家展示了如何理解tcpServer 中的IOLoop方法，内容简明扼要并且容易理解，绝对能使你眼前一亮，通过这篇文章的详细介绍希望你能有所收获。
今天我们就分析一下IOLoop这个方法
废话不多说，直接上代码吧（代码位于nsq/nsqlookupd/lookup_protocol_v1.go这个文件中）
//这段代码位于nsq/nsqlookupd/client_v1.go这个文件中type ClientV1 struct {net.Conn //组合net.Conn接口peerInfo *PeerInfo //client的信息也就是前面所讲的product的信息}//初始化一个ClientV1func NewClientV1(conn net.Conn) *ClientV1 {return &ClientV1{Conn: conn,}}//实现String接口func (c *ClientV1) String() string {return c.RemoteAddr().String()}//定义ClientV1结束type LookupProtocolV1 struct {ctx *Context //一直贯穿整个代码的Context，具体可翻看前面章节}func (p *LookupProtocolV1) IOLoop(conn net.Conn) error {var err errorvar line stringclient := NewClientV1(conn) //新建一个client版本为V1err = nilreader := bufio.NewReader(client) //由client 创建一个 带有buffer 的Reader 默认 buffer size 为4096，这里的NewReader参数为io.Reader 接口，为何net.Conn接口也能作为参数呢？因为net.Conn 接口其实也是实现了io.Reader接口了，具体概念大家可翻看golang的教程for {line, err = reader.ReadString('\n') //按行读取if err != nil {break}line = strings.TrimSpace(line) //去掉这行两头的空格符params := strings.Split(line, " ") //字符串按一个空格字符串分割，并获取相应的Commad 以及 该command 的相应的paramsresponse, err := p.Exec(client, reader, params) //执行相应的Commandif err != nil {ctx := ""if parentErr := err.(protocol.ChildErr).Parent(); parentErr != nil {ctx = " - " + parentErr.Error()}p.ctx.nsqlookupd.logf("ERROR: [%s] - %s%s", client, err, ctx)_, err = protocol.SendResponse(client, []byte(err.Error())) //返回错误给clientif err != nil {break}// errors of type FatalClientErr should forceably close the connectionif _, ok := err.(*protocol.FatalClientErr); ok { break}continue}if response != nil {_, err = protocol.SendResponse(client, response) //返回命令处理结果给clientif err != nil {break}}}//for 循环结束了 说明程序要退出了，调用RegistrationDB 中的 RemoveProducer从producer 的注册数据中删除 producer信息//这里的RegistrationDB下章再具体讲解p.ctx.nsqlookupd.logf("CLIENT(%s): closing", client)if client.peerInfo != nil {registrations := p.ctx.nsqlookupd.DB.LookupRegistrations(client.peerInfo.id)for _, r := range registrations {if removed, _ := p.ctx.nsqlookupd.DB.RemoveProducer(r, client.peerInfo.id); removed {p.ctx.nsqlookupd.logf("DB: client(%s) UNREGISTER category:%s key:%s subkey:%s",client, r.Category, r.Key, r.SubKey)}}}return err}//这个方法就是执行相应的命令动作 有 PING IDENTIFY REGISTER UNREGISTER 这四个类型func (p *LookupProtocolV1) Exec(client *ClientV1, reader *bufio.Reader, params []string) ([]byte, error) {switch params[0] {case "PING": //用于client的心跳处理return p.PING(client, params)case "IDENTIFY": //用于client端的信息注册，执行PING REGISTER UNREGISTER 命令前必须先执行此命令return p.IDENTIFY(client, reader, params[1:])case "REGISTER": //用于client端注册topic以及channel的命令return p.REGISTER(client, reader, params[1:])case "UNREGISTER": //执行与REGISTER命令相反的逻辑return p.UNREGISTER(client, reader, params[1:])}return nil, protocol.NewFatalClientErr(nil, "E_INVALID", fmt.Sprintf("invalid command %s", params[0]))}//INDENTIFY命令处理逻辑//该命令用于注册client的producer信息，并返回nsqlookupd的TCP 以及 HTTP 端口信息给client//大致的报文如下// V1 INDENTIFY\n 注意了这里前面提过的V1前面是两个空格字符//123\n 这里是后面json数据（producer 信息的json数据的字节长度）//{....}\n 一串表示producer信息的json数据，具体的可参考 nsq/nsqlookupd/registration_db.go文件中的PeerInfo structfunc (p *LookupProtocolV1) IDENTIFY(client *ClientV1, reader *bufio.Reader, params []string) ([]byte, error) {var err errorif client.peerInfo != nil { //如果有该client 的PeerInfo数据则返回错误return nil, protocol.NewFatalClientErr(err, "E_INVALID", "cannot IDENTIFY again")}var bodyLen int32err = binary.Read(reader, binary.BigEndian, &bodyLen) //获取producer PeerInfo json数据的字节长度 大端二进制格式if err != nil {return nil, protocol.NewFatalClientErr(err, "E_BAD_BODY", "IDENTIFY failed to read body size")}body := make([]byte, bodyLen) //初始化一个producer PeerInfo json数据长度的bytes_, err = io.ReadFull(reader, body) //读取所有的json数据if err != nil {return nil, protocol.NewFatalClientErr(err, "E_BAD_BODY", "IDENTIFY failed to read body")}// body is a json structure with producer informationpeerInfo := PeerInfo{id: client.RemoteAddr().String()} //实例化一个PeerInfoerr = json.Unmarshal(body, &peerInfo) //解析producer PeerInfo json数据到peerInfoif err != nil {//json 数据解析失败 返回错误return nil, protocol.NewFatalClientErr(err, "E_BAD_BODY", "IDENTIFY failed to decode JSON body")}peerInfo.RemoteAddress = client.RemoteAddr().String() //获取PeerInfo remote address// require all fields//校验获取的PeerInfo 数据if peerInfo.BroadcastAddress == "" || peerInfo.TCPPort == 0 || peerInfo.HTTPPort == 0 || peerInfo.Version == "" {return nil, protocol.NewFatalClientErr(nil, "E_BAD_BODY", "IDENTIFY missing fields")}//将当前系统时间（纳秒）更新到PeerInfo 中的lastUpdate中 用于 client的心跳判断atomic.StoreInt64(&peerInfo.lastUpdate, time.Now().UnixNano())p.ctx.nsqlookupd.logf("CLIENT(%s): IDENTIFY Address:%s TCP:%d HTTP:%d Version:%s",client, peerInfo.BroadcastAddress, peerInfo.TCPPort, peerInfo.HTTPPort, peerInfo.Version)client.peerInfo = &peerInfo//注册producer PeerInfo 信息到 RegistrationDB中 其中Registration的 Category 为client Key 和 SubKey为空if p.ctx.nsqlookupd.DB.AddProducer(Registration{"client", "", ""}, &Producer{peerInfo: client.peerInfo}) {p.ctx.nsqlookupd.logf("DB: client(%s) REGISTER category:%s key:%s subkey:%s", client, "client", "", "")}// build a response//将nsqlookupd的TCP端口，HTTP端口信息，版本信息，broadcast address信息，以及host name信息 已json数据格式返回给clientdata := make(map[string]interface{})data["tcp_port"] = p.ctx.nsqlookupd.RealTCPAddr().Portdata["http_port"] = p.ctx.nsqlookupd.RealHTTPAddr().Portdata["version"] = version.Binaryhostname, err := os.Hostname()if err != nil {log.Fatalf("ERROR: unable to get hostname %s", err)}data["broadcast_address"] = p.ctx.nsqlookupd.opts.BroadcastAddressdata["hostname"] = hostnameresponse, err := json.Marshal(data)if err != nil {p.ctx.nsqlookupd.logf("ERROR: marshaling %v", data)return []byte("OK"), nil}return response, nil}//获取params中的topic 以及 channelfunc getTopicChan(command string, params []string) (string, string, error) {if len(params) == 0 {return "", "", protocol.NewFatalClientErr(nil, "E_INVALID", fmt.Sprintf("%s insufficient number of params", command))}topicName := params[0]var channelName stringif len(params) >= 2 {channelName = params[1]}//校验是否是topicif !protocol.IsValidTopicName(topicName) {return "", "", protocol.NewFatalClientErr(nil, "E_BAD_TOPIC", fmt.Sprintf("%s topic name '%s' is not valid", command, topicName))}//校验是否是channelif channelName != "" && !protocol.IsValidChannelName(channelName) {return "", "", protocol.NewFatalClientErr(nil, "E_BAD_CHANNEL", fmt.Sprintf("%s channel name '%s' is not valid", command, channelName))}return topicName, channelName, nil}//REGISTER 命令 用于注册client的topic 以及 channel信息//一个topic下可以有多个channel//一个消费者订阅的是一个topic 那么 生成者给这个topic 下的channel的信息 这个消费者也能接收得到这个信息，如果消费者订阅的不是这个channel的信息，那么这个消费者则接受不到这个信息//nsq topic 与channel的关系，大家可以多搜索下资料，我这里感觉讲的也不太清晰，请大家谅解一下//REGISTER 命令必须在INDENTIFY 之后才能调用//具体协议报文如下//REGISTER topic1\n 这个只创建一个名字为topic1的topic//或如下报文//REGISTER topic1 channel1\n 这个只创建一个名字为topic1的topic 且topic1下面创建一个名字为channel1的channelfunc (p *LookupProtocolV1) REGISTER(client *ClientV1, reader *bufio.Reader, params []string) ([]byte, error) {if client.peerInfo == nil {return nil, protocol.NewFatalClientErr(nil, "E_INVALID", "client must IDENTIFY")}//获取REGISTER 命令时的topic 以及channel名字topic, channel, err := getTopicChan("REGISTER", params) if err != nil {return nil, err}//如果有channelif channel != "" {//添加channel信息到RegistrationDB中其中Registration的 Category 为"channel"字符串，Key为topic，SubKey为channelkey := Registration{"channel", topic, channel}if p.ctx.nsqlookupd.DB.AddProducer(key, &Producer{peerInfo: client.peerInfo}) {p.ctx.nsqlookupd.logf("DB: client(%s) REGISTER category:%s key:%s subkey:%s",client, "channel", topic, channel)}}//添加topic信息到RegistrationDB中其中Registration的 Category 为"topic"字符串，Key为topic，SubKey为空key := Registration{"topic", topic, ""}if p.ctx.nsqlookupd.DB.AddProducer(key, &Producer{peerInfo: client.peerInfo}) {p.ctx.nsqlookupd.logf("DB: client(%s) REGISTER category:%s key:%s subkey:%s",client, "topic", topic, "")}//返回OKreturn []byte("OK"), nil}//UNREGISTER命令用于取消注册topic 或取消注册某个topic下的某一个channel//报文格式如下//UNREGISTER topic1 channel1\n 这个报文表示取消注册名字为topic1的topic下的名字为channel1的channel，这个名字 只取消注册这个channel1，不取消注册topic1下的其他channel 以及这个topic1本身//或这个格式的报文//UNREGISTER topic1\n 这个报文表示取消注册名字为topic1的topic，这个时候topic1以及topic1下的所有channel都取消注册了func (p *LookupProtocolV1) UNREGISTER(client *ClientV1, reader *bufio.Reader, params []string) ([]byte, error) {if client.peerInfo == nil {return nil, protocol.NewFatalClientErr(nil, "E_INVALID", "client must IDENTIFY")}topic, channel, err := getTopicChan("UNREGISTER", params) //获取topic 以及channel 的名字if err != nil {return nil, err}if channel != "" {//如果有channel 则只取消注册这个topic下的这个channelkey := Registration{"channel", topic, channel}removed, left := p.ctx.nsqlookupd.DB.RemoveProducer(key, client.peerInfo.id)if removed {p.ctx.nsqlookupd.logf("DB: client(%s) UNREGISTER category:%s key:%s subkey:%s",client, "channel", topic, channel)}// for ephemeral channels, remove the channel as well if it has no producersif left == 0 && strings.HasSuffix(channel, "#ephemeral") {p.ctx.nsqlookupd.DB.RemoveRegistration(key)}} else {// no channel was specified so this is a topic unregistration// remove all of the channel registrations...// normally this shouldn't happen which is why we print a warning message// if anything is actually removed//如果没有channel 这个取消注册这个topic 以及这个topic下的所有channelregistrations := p.ctx.nsqlookupd.DB.FindRegistrations("channel", topic, "*")for _, r := range registrations {if removed, _ := p.ctx.nsqlookupd.DB.RemoveProducer(r, client.peerInfo.id); removed {p.ctx.nsqlookupd.logf("WARNING: client(%s) unexpected UNREGISTER category:%s key:%s subkey:%s",client, "channel", topic, r.SubKey)}}key := Registration{"topic", topic, ""}if removed, _ := p.ctx.nsqlookupd.DB.RemoveProducer(key, client.peerInfo.id); removed {p.ctx.nsqlookupd.logf("DB: client(%s) UNREGISTER category:%s key:%s subkey:%s",client, "topic", topic, "")}}//返回OKreturn []byte("OK"), nil}//PING 用于client中的心跳处理命令func (p *LookupProtocolV1) PING(client *ClientV1, params []string) ([]byte, error) {if client.peerInfo != nil {// we could get a PING before other commands on the same client connection//获取上一次心跳的时间cur := time.Unix(0, atomic.LoadInt64(&client.peerInfo.lastUpdate))//获取当前时间now := time.Now()//这里日志输出两次心跳之间的间隔时间p.ctx.nsqlookupd.logf("CLIENT(%s): pinged (last ping %s)", client.peerInfo.id,now.Sub(cur))//更新PeerInfo中的lastUpdate时间为当前时间atomic.StoreInt64(&client.peerInfo.lastUpdate, now.UnixNano())}//返回OKreturn []byte("OK"), nil}nsqlookupd中的tcpServer中的主要协议处理的IOLoop这里基本讲解完了。
上述内容就是如何理解tcpServer 中的IOLoop方法，你们学到知识或技能了吗？如果还想学到更多技能或者丰富自己的知识储备，欢迎关注编程网行业资讯频道。
