聊聊nacos-coredns-plugin的UDPServer

Posted 2021-09-28 codecraft

序

本文主要研究一下nacos-coredns-plugin的UDPServer

UDPServer

nacos-coredns-plugin/nacos/udp_server.go

type UDPServer struct {
    port int
    host string
    vipClient *NacosClient
}

UDPServer定义了port、host、vipClient属性

StartServer

nacos-coredns-plugin/nacos/udp_server.go

func (us *UDPServer) 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
            NacosClientLogger.Info("udp server start, port: " + strconv.Itoa(port))
            break
        }

        if !ok && i == 2 {
            NacosClientLogger.Critical("failed to start udp server after trying 3 times.")
            os.Exit(1)
        }
    }

    UDP_Port = us.port

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

StartServer方法循环3次执行tryListen()，若都没有成功则exit；若成功则for循环执行handleClient

tryListen

nacos-coredns-plugin/nacos/udp_server.go

func (us *UDPServer) tryListen() (*net.UDPConn, bool) {
    addr, err := net.ResolveUDPAddr("udp", us.host+":"+ strconv.Itoa(us.port))
    if err != nil {
        NacosClientLogger.Error("Can\'t resolve address: ", err)
        return nil , false
    }

    conn, err := net.ListenUDP("udp", addr)
    if err != nil {
        NacosClientLogger.Error("Error listening:", err)
        return nil, false
    }

    return conn, true
}

tryListen方法先执行net.ResolveUDPAddr，在执行net.ListenUDP

handleClient

nacos-coredns-plugin/nacos/udp_server.go

type PushData struct {
    PushType string `json:"type"`
    Data string `json:"data"`
    LastRefTime int64 `json:"lastRefTime"`
    
}

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

    s := TryDecompressData(data[:n])

    NacosClientLogger.Info("receive push: " + s + " from: ", remoteAddr)

    var pushData PushData
    err1 := json.Unmarshal([]byte(s), &pushData)
    if err1 != nil {
        NacosClientLogger.Warn("failed to process push data, ", err1)
        return
    }

    domain, err1 := ProcessDomainString(pushData.Data)
    NacosClientLogger.Info("receive domain: " , domain)

    if err1 != nil {
        NacosClientLogger.Warn("failed to process push data: " + s, err1)
    }

    key := GetCacheKey(domain.Name, LocalIP())

    us.vipClient.domainMap.Set(key, domain)

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

    bs,_ := json.Marshal(ack)

    conn.WriteToUDP(bs, remoteAddr)
}

handleClient方法执行conn.ReadFromUDP，然后通过TryDecompressData解压数据，然后Unmarshal为PushData类型，执行ProcessDomainString获取domain，执行us.vipClient.domainMap.Set(key, domain)，最后构造返回数据ack回去

小结

nacos-coredns-plugin的UDPServer定义了port、host、vipClient属性；它提供了StartServer方法；StartServer方法循环3次执行tryListen()，若都没有成功则exit；若成功则for循环执行handleClient。

doc

• nacos-coredns-plugin