如何理解tcpServer 中的IOLoop方法

//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ClientV1 func 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 error var line string client := NewClientV1(conn) //新建一个client版本为V1 err = nil reader := 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params response, err := p.Exec(client, reader, params) //执行相应的Command if 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client if err != nil { break } // errors of type FatalClientErr should forceably close the connection if _, ok := err.(*protocol.FatalClientErr); ok { break } continue } if response != nil { _, err = protocol.SendResponse(client, response) //返回命令处理结果给client if 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 struct func (p *LookupProtocolV1) IDENTIFY(client *ClientV1, reader *bufio.Reader, params []string) ([]byte, error) { var err error if 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 int32 err = 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 information peerInfo := PeerInfo{id: client.RemoteAddr().String()} //实例化一个PeerInfo err = json.Unmarshal(body, &peerInfo) //解析producer PeerInfo json数据到peerInfo if 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client data := make(map[string]interface{}) data["tcp_port"] = p.ctx.nsqlookupd.RealTCPAddr().Port data["http_port"] = p.ctx.nsqlookupd.RealHTTPAddr().Port data["version"] = version.Binary hostname, err := os.Hostname() if err != nil { log.Fatalf("ERROR: unable to get hostname %s", err) } data["broadcast_address"] = p.ctx.nsqlookupd.opts.BroadcastAddress data["hostname"] = hostname response, 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 channel func 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 string if len(params) >= 2 { channelName = params[1] } //校验是否是topic if !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channel if 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channel func (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channel if channel != "" { //添加channel信息到RegistrationDB中其中Registration的 Category 为"channel"字符串，Key为topic，SubKey为channel key := 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OK return []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channel key := 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 producers if 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channel registrations := 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OK return []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OK return []byte("OK"), nil }

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