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