关于golang:聊聊nacoscorednsplugin的UDPServer

序

本文次要钻研一下 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 办法循环 3 次执行 tryListen()，若都没有胜利则 exit；若胜利则 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 办法先执行 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 办法执行 conn.ReadFromUDP，而后通过 TryDecompressData 解压数据，而后 Unmarshal 为 PushData 类型，执行 ProcessDomainString 获取 domain，执行 us.vipClient.domainMap.Set(key, domain)，最初结构返回数据 ack 回去

小结

nacos-coredns-plugin 的 UDPServer 定义了 port、host、vipClient 属性；它提供了 StartServer 办法；StartServer 办法循环 3 次执行 tryListen()，若都没有胜利则 exit；若胜利则 for 循环执行 handleClient。

doc

• nacos-coredns-plugin