Question

我正在使用System.Net.Http.HttpClient发出postaysnc请求。在请求进行过程中，我拔下网络电缆，接收HttpRequestException。一段时间后，再次插入网络电缆并发出postasync请求，得到HttpRequestException-有时我得到响应服务器不可用，有时超时我是否需要在异常情况下处理httpclient并在发出请求时重新创建？如何使查询在网络还原中成功。

    private async Task<string> GetServerResult()
    {
        try
        {
            var response = await myHttpClient.PostAsync("https://google.com", httpContent);
            response.EnsureSuccessStatusCode();
        }
        catch (HttpRequestException ex)
        {
            throw new HttpRequestException(ex.Message, ex.InnerException);
        }
    }

Answer 1

根据您的要求，在这种情况下，您必须更改实现某种实现。我提出的解决方案用于WCF客户端的缓存机制，并定期对其进行更新。

非常简单的实现可能是：您有一个非常简单的singleton类，并且定期Timer从您提到的端点中获取数据。它存储了最后缓存的数据，以便您拥有数据的副本；当匹配失败时，您可以为此配置后备机制。例如，您有一个类似

的实现

//You single Cache class
public sealed class ClientCache
{
     #region Singleton implementation
     private static  ClientCache _clientCache = new ClientCache();


     private ClientCache()
     {

     }

     public static ClientCache Instance => _clientCache;    
     #endregion

     //Timer for syncing the data from Server
     private Timer _timer;
     //This data is the cached one
     public string data = string.Empty;

     internal void StartProcess()
     {
            //Initializing the timer
            _timer = new Timer(TimeSpan.FromMinutes(1).TotalMilliseconds); //This timespan is configurable
            //Assigning it an elapsed time event
            _timer.Elapsed += async (e, args) => await SyncServerData(e, args);
            //Starting the timer 
            _timer.Start();

     } 

     //In this method you will request your server and fetch the latest copy of the data
     //In case of failure you can maintain the history of the last disconnected server
     private async Task ProcessingMethod(object sender, ElapsedEventArgs e)
     {
         //First we will stop the timer so that any other hit don't come in the mean while
         timer.Stop();

         //Call your api here 
         //Once the hit is completed or failed 
         //On Success you will be updating the Data object
         //data = result from your api call  

         //Finally start the time again as
         timer.Start();
     } 

}

现在进入第二步，初始化ClientCache类。最好的选择是在Global.asax类中对其进行初始化

protected void Application_Start()
{           
      //As
      ClientCache.Instance.StartProcess();
}

现在，只要您的前端调用该方法，您就无需返回服务器。只需将缓存中的结果发送回：

private Task<string> GetServerResult()
{
     return Task.FromResult(ClientCache.Instance.data);
}

HttpClient在网络还原上引发httprequest异常

1 个答案: