聊聊nacos-coredns-plugin的ServerManager

序

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

ServerManager

nacos-coredns-plugin/nacos/server_manager.go

type ServerManager struct {
	serverList      []string
	lastRefreshTime int64
	cursor          int
}

// get nacos ip list from address by env
func (manager *ServerManager) RefreshServerListIfNeed() []string {
	if CurrentMillis()-manager.lastRefreshTime < 60*1000 && len(manager.serverList) > 0 {
		return manager.serverList
	}

	nacosServerList := os.Getenv("nacos_server_list")

	var list []string
	list = strings.Split(nacosServerList, ",")

	var servers []string
	for _, line := range list {
		if line != "" {
			servers = append(servers, strings.TrimSpace(line))
		}
	}

	if len(servers) > 0 {
		if !reflect.DeepEqual(manager.serverList, servers) {
			NacosClientLogger.Info("server list is updated, old: ", manager.serverList, ", new: ", servers)
		}
		manager.serverList = servers

		manager.lastRefreshTime = CurrentMillis()
	}

	return manager.serverList
}

func (manager *ServerManager) NextServer() string {
	manager.RefreshServerListIfNeed()

	if len(manager.serverList) == 0 {
		panic("no nacos server avialible.")
	}

	return manager.serverList[rand.Intn(len(manager.serverList))]
}

func (manager *ServerManager) SetServers(servers []string) {
	manager.serverList = servers
}

func (manager *ServerManager) GetServerList() []string {
	return manager.serverList
}

ServerManager定義了serverList、lastRefreshTime、cursor屬性；它提供了RefreshServerListIfNeed、NextServer、SetServers、GetServerList方法；其中NextServer會先執行RefreshServerListIfNeed在返回隨機的server；RefreshServerListIfNeed方法會根據lastRefreshTime來判斷是否需要refresh，若要refresh則重新通過os.Getenv("nacos_server_list")獲取server列表，然後更新lastRefreshTime

實例

nacos-coredns-plugin/nacos/server_manager_test.go

func TestServerManager_NextServer(t *testing.T) {
	os.Setenv("nacos_server_list", "2.2.2.2,3.3.3.3")
	sm := ServerManager{}
	sm.RefreshServerListIfNeed()
	ip := sm.NextServer()
	if strings.Compare(ip, "2.2.2.2") == 0 ||
		strings.Compare(ip, "3.3.3.3") == 0 {
		t.Log("ServerManager.NextServer test is passed.")
	}
}

func TestServerManager_RefreshServerListIfNeed(t *testing.T) {
	os.Setenv("nacos_server_list", "2.2.2.2,3.3.3.3")
	sm := ServerManager{}
	sm.RefreshServerListIfNeed()

	if len(sm.serverList) == 2 {
		t.Log("ServerManager.RefreshServerListIfNeed test is passed.")
	}

}

小結

nacos-coredns-plugin的ServerManager定義了serverList、lastRefreshTime、cursor屬性；它提供了RefreshServerListIfNeed、NextServer、SetServers、GetServerList方法。

doc

• nacos-coredns-plugin