c# - 如何处理 WCF 异常(带代码的综合列表)

Question

我正在尝试扩展 this answer on SO使 WCF 客户端重试暂时性网络故障并处理 other situations that require a retry such as authentication expiration.

问题:

需要处理的WCF异常有哪些，正确的处理方式是什么？

以下是我希望看到的一些示例技术，它们可以代替 proxy.abort() 或作为补充:

• 重试前延迟 X 秒
• 关闭并重新创建一个 New() WCF 客户端。处理掉旧的。
• 不要重试并重新抛出此错误
• 重试N次，然后抛出

由于不可能有人知道所有异常或解决它们的方法，因此请分享您所知道的。我将在下面的代码示例中汇总答案和方法。

    // USAGE SAMPLE
    //int newOrderId = 0; // need a value for definite assignment
    //Service<IOrderService>.Use(orderService=>
    //{
    //  newOrderId = orderService.PlaceOrder(request);
    //}




    /// <summary>
    /// A safe WCF Proxy suitable when sessionmode=false
    /// </summary>
    /// <param name="codeBlock"></param>
    public static void Use(UseServiceDelegateVoid<T> codeBlock)
    {
        IClientChannel proxy = (IClientChannel)_channelFactory.CreateChannel();
        bool success = false;
        try
        {
            codeBlock((T)proxy);
            proxy.Close();
            success = true;
        }
        catch (CommunicationObjectAbortedException e)
        {
                // Object should be discarded if this is reached.  
                // Debugging discovered the following exception here:
                // "Connection can not be established because it has been aborted" 
            throw e;
        }
        catch (CommunicationObjectFaultedException e)
        {
            throw e;
        }
        catch (MessageSecurityException e)
        {
            throw e;
        }
        catch (ChannelTerminatedException)
        {
            proxy.Abort(); // Possibly retry?
        }
        catch (ServerTooBusyException)
        {
            proxy.Abort(); // Possibly retry?
        }
        catch (EndpointNotFoundException)
        {
            proxy.Abort(); // Possibly retry?
        }
        catch (FaultException)
        {
            proxy.Abort();
        }
        catch (CommunicationException)
        {
            proxy.Abort();
        }
        catch (TimeoutException)
        {
         // Sample error found during debug: 

         // The message could not be transferred within the allotted timeout of 
         //  00:01:00. There was no space available in the reliable channel's 
         //  transfer window. The time allotted to this operation may have been a 
         //  portion of a longer timeout.

            proxy.Abort();
        }
        catch (ObjectDisposedException )
        {
            //todo:  handle this duplex callback exception.  Occurs when client disappears.  
            // Source: https://stackoverflow.com/questions/1427926/detecting-client-death-in-wcf-duplex-contracts/1428238#1428238
        }
        finally
        {
            if (!success)
            {
                proxy.Abort();
            }
        }
    }

Answer 1

编辑:多次关闭和重新打开客户端似乎效率低下。我是 exploring solutions here如果找到，将更新和扩展此代码。 (或者如果 David Khaykin 发布了一个答案，我会将其标记为已接受)

经过几年的修改，下面的代码是我处理 WCF 重试和处理异常的首选策略 ( after seeing this blog posting from the wayback machine)。

我调查了每一个异常，我想对那个异常做什么，并注意到一个共同的特征；每个需要从公共(public)基类继承的“重试”的异常。我还注意到，每个将客户端置于无效状态的 permFail 异常也来自共享基类。

以下示例捕获客户端可以通过的每个 WCF 异常，并且可以针对您自己的自定义 channel 错误进行扩展。

WCF 客户端使用示例

生成客户端代理后，您只需执行此操作即可。

Service<IOrderService>.Use(orderService=>
{
  orderService.PlaceOrder(request);
}

ServiceDelegate.cs

将此文件添加到您的解决方案中。不需要对此文件进行任何更改，除非您想更改重试次数或要处理的异常。

public delegate void UseServiceDelegate<T>(T proxy);

public static class Service<T>
{
    public static ChannelFactory<T> _channelFactory = new ChannelFactory<T>(""); 

    public static void Use(UseServiceDelegate<T> codeBlock)
    {
        IClientChannel proxy = null;
        bool success = false;


       Exception mostRecentEx = null;
       int millsecondsToSleep = 1000;

       for(int i=0; i<5; i++)  // Attempt a maximum of 5 times 
       {
           // Proxy cann't be reused
           proxy = (IClientChannel)_channelFactory.CreateChannel();

           try
           {
               codeBlock((T)proxy);
               proxy.Close();
               success = true; 
               break;
           }
           catch (FaultException customFaultEx)
           {
               mostRecentEx = customFaultEx;
               proxy.Abort();

               //  Custom resolution for this app-level exception
               Thread.Sleep(millsecondsToSleep * (i + 1)); 
           }

           // The following is typically thrown on the client when a channel is terminated due to the server closing the connection.
           catch (ChannelTerminatedException cte)
           {
              mostRecentEx = cte;
               proxy.Abort();
               //  delay (backoff) and retry 
               Thread.Sleep(millsecondsToSleep  * (i + 1)); 
           }

           // The following is thrown when a remote endpoint could not be found or reached.  The endpoint may not be found or 
           // reachable because the remote endpoint is down, the remote endpoint is unreachable, or because the remote network is unreachable.
           catch (EndpointNotFoundException enfe)
           {
              mostRecentEx = enfe;
               proxy.Abort();
               //  delay (backoff) and retry 
               Thread.Sleep(millsecondsToSleep * (i + 1)); 
           }

           // The following exception that is thrown when a server is too busy to accept a message.
           catch (ServerTooBusyException stbe)
           {
              mostRecentEx = stbe;
               proxy.Abort();

               //  delay (backoff) and retry 
               Thread.Sleep(millsecondsToSleep * (i + 1)); 
           }
           catch (TimeoutException timeoutEx)
           {
               mostRecentEx = timeoutEx;
               proxy.Abort();

               //  delay (backoff) and retry 
               Thread.Sleep(millsecondsToSleep * (i + 1)); 
           } 
           catch (CommunicationException comException)
           {
               mostRecentEx = comException;
               proxy.Abort();

               //  delay (backoff) and retry 
               Thread.Sleep(millsecondsToSleep * (i + 1)); 
           }


           catch(Exception e)
           {
                // rethrow any other exception not defined here
                // You may want to define a custom Exception class to pass information such as failure count, and failure type
                proxy.Abort();
                throw e;  
           }
       }
       if (success == false && mostRecentEx != null) 
       { 
           proxy.Abort();
           throw new Exception("WCF call failed after 5 retries.", mostRecentEx );
       }

    }
}