关于golang:聊聊nacoscorednsplugin的ServerManager

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本文次要钻研一下 nacos-coredns-plugin 的 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 定义了 serverList、lastRefreshTime、cursor 属性；它提供了 RefreshServerListIfNeed、NextServer、SetServers、GetServerList 办法；其中 NextServer 会先执行 RefreshServerListIfNeed 在返回随机的 server；RefreshServerListIfNeed 办法会依据 lastRefreshTime 来判断是否须要 refresh，若要 refresh 则从新通过 os.Getenv(“nacos_server_list”) 获取 server 列表，而后更新 lastRefreshTime

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.")
    }

}

nacos-coredns-plugin 的 ServerManager 定义了 serverList、lastRefreshTime、cursor 属性；它提供了 RefreshServerListIfNeed、NextServer、SetServers、GetServerList 办法。