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