聊聊nacos-sdk-go的PushReceiver

序

本文主要研究一下nacos-sdk-go的PushReceiver

PushReceiver

nacos-sdk-go-v0.3.2/clients/naming_client/push_receiver.go

type PushReceiver struct {
	port        int
	host        string
	hostReactor *HostReactor
}

• PushReceiver定义了port、host、hostReactor属性

NewPushRecevier

nacos-sdk-go-v0.3.2/clients/naming_client/push_receiver.go

func NewPushRecevier(hostReactor *HostReactor) *PushReceiver {
	pr := PushReceiver{
		hostReactor: hostReactor,
	}
	go pr.startServer()
	return &pr
}

• NewPushRecevier方法创建PushReceiver，并异步执行pr.startServer()

startServer

nacos-sdk-go-v0.3.2/clients/naming_client/push_receiver.go

func (us *PushReceiver) startServer() {
	var conn *net.UDPConn

	for i := 0; i < 3; i++ {
		r := rand.New(rand.NewSource(time.Now().UnixNano()))
		port := r.Intn(1000) + 54951
		us.port = port
		conn1, ok := us.tryListen()

		if ok {
			conn = conn1
			log.Println("[INFO] udp server start, port: " + strconv.Itoa(port))
			break
		}

		if !ok && i == 2 {
			log.Panicf("failed to start udp server after trying 3 times.")
			//os.Exit(1)  //It is weird dangerous to invoke the os.Exit() as a Middleware.
		}
	}

	defer conn.Close()
	for {
		us.handleClient(conn)
	}
}

• startServer方法随机执行一个端口，然后执行us.tryListen()，三次不成功则退出，成功则执行us.handleClient(conn)

tryListen

nacos-sdk-go-v0.3.2/clients/naming_client/push_receiver.go

func (us *PushReceiver) tryListen() (*net.UDPConn, bool) {
	addr, err := net.ResolveUDPAddr("udp", us.host+":"+strconv.Itoa(us.port))
	if err != nil {
		log.Printf("[ERROR]: Can't resolve address,err: %s \n", err.Error())
		return nil, false
	}

	conn, err := net.ListenUDP("udp", addr)
	if err != nil {
		log.Printf("Error listening %s:%d,err:%s \n", us.host, us.port, err.Error())
		return nil, false
	}

	return conn, true
}

• tryListen方法先执行net.ResolveUDPAddr，然后执行net.ListenUDP("udp", addr)

handleClient

nacos-sdk-go-v0.3.2/clients/naming_client/push_receiver.go

func (us *PushReceiver) handleClient(conn *net.UDPConn) {
	data := make([]byte, 4024)
	n, remoteAddr, err := conn.ReadFromUDP(data)
	if err != nil {
		log.Printf("[ERROR]:failed to read UDP msg because of %s \n", err.Error())
		return
	}

	s := utils.TryDecompressData(data[:n])
	log.Println("[INFO] receive push: "+s+" from: ", remoteAddr)

	var pushData PushData
	err1 := json.Unmarshal([]byte(s), &pushData)
	if err1 != nil {
		log.Printf("[ERROR] failed to process push data.err:%s \n", err1.Error())
		return
	}
	ack := make(map[string]string)

	if pushData.PushType == "dom" || pushData.PushType == "service" {
		us.hostReactor.ProcessServiceJson(pushData.Data)

		ack["type"] = "push-ack"
		ack["lastRefTime"] = strconv.FormatInt(pushData.LastRefTime, 10)
		ack["data"] = ""

	} else if pushData.PushType == "dump" {
		ack["type"] = "dump-ack"
		ack["lastRefTime"] = strconv.FormatInt(pushData.LastRefTime, 10)
		ack["data"] = utils.ToJsonString(us.hostReactor.serviceInfoMap)
	} else {
		ack["type"] = "unknow-ack"
		ack["lastRefTime"] = strconv.FormatInt(pushData.LastRefTime, 10)
		ack["data"] = ""
	}

	bs, _ := json.Marshal(ack)
	conn.WriteToUDP(bs, remoteAddr)
}

• handleClient方法通过conn.ReadFromUDP(data)接受数据，然后通过utils.TryDecompressData解压，再通过json.Unmarshal([]byte(s), &pushData)解析为PushData，之后根据pushData.PushType构造ack数据，最后通过conn.WriteToUDP(bs, remoteAddr)响应回去

小结

PushReceiver定义了port、host、hostReactor属性；它提供了NewPushRecevier、startServer、handleClient等方法

doc

• push_receiver

来源：oschina

链接：https://my.oschina.net/go4it/blog/4329223