使用ELMAH的WCF服务的异常记录 [英] Exception Logging for WCF Services using ELMAH

问题描述

我们正在使用优秀的 ELMAH 来处理ASP.NET 3.5网络中未处理的异常应用。除了使用REST功能使用的WCF服务之外，这对所有站点都非常有效。当操作方法中出现异常时，不由应用程序代码处理，WCF会根据服务契约和配置设置以各种方式处理异常。这意味着异常不会最终触发 ELMAH 使用的ASP.NET HttpApplication.Error事件。我想知道的两个解决方案是：

We are using the excellent ELMAH to deal with unhandled exceptions in an ASP.NET 3.5 web application. This works extremely well for all of the site apart from WCF services which are being consumed using the REST features. When an exception occurs within the operation methods that is not handled by the application code, WCF handles it in various ways depending on the service contracts and configuration settings. This means that the exception does not end up firing the ASP.NET HttpApplication.Error event that ELMAH uses. The two solutions I am aware of to deal with this are:

• 将try {} catch（Exception ex）{ 。Elmah.ErrorSignal.FromCurrentContext（）提高（前）;扔; }在catch块中显式调用Elmah。


• 使用 IErrorHandler ，如 Will Hughes'所述博客文章使WCF和ELMAH一起玩得很好将对ELMAH的调用除以单独的ErrorHandler。

• Wrap all method calls in a try { } catch(Exception ex) { Elmah.ErrorSignal.FromCurrentContext().Raise(ex); throw; } to explicitly call Elmah within the catch block.
• Use IErrorHandler as described in Will Hughes' blog post Making WCF and ELMAH play nice together to factor out the call to ELMAH to a separate ErrorHandler.

第一个选项非常简单，但不完全是 DRY 。第二个选项只需要在实现属性和ErrorHandler之后，使用自定义属性来装饰每个服务。我已经根据 Will的工作做了这个工作，但我想验证这是否是

The first option is extremely simple but is not exactly DRY. The second option only requires you to decorate each service with the custom attribute after implementing the attribute and the ErrorHandler. I have done this based on Will's work but I want to verify that this is the correct approach before posting the code.

有没有更好的方法，我错过了？

IErrorHandler的MSDN文档表示， HandleError 方法是进行日志记录的地方，但 ELMAH 访问HttpContext.Current。 ApplicationInstance ，即使HttpContext.Current可用，此方法为null。在ProvideFault方法中调用Elmah是一种解决方法，因为ApplicationInstance已设置，但这与API文档中描述的意图不符。 我在这里缺少某些东西？文档确实说明您不应该依赖于在操作线程上调用的HandleError方法，这可能是此范围中的ApplicationInstance为null。

The MSDN documenation for IErrorHandler says that the HandleError method is the place to do the logging but ELMAH accesses the HttpContext.Current.ApplicationInstance, which is null within this method even though HttpContext.Current is available. Making the call to Elmah within the ProvideFault method is a workaround as ApplicationInstance is set but this does not match the intent described in the API documentation. Am I missing something here? The documentation does state that you should not rely on the HandleError method being called on the operation thread which may be why ApplicationInstance is null in this scope.

推荐答案

我的博文（在OP中引用）的解决方案是基于我们正在/正在使用的现有解决方案，以在错误状态下更改HTTP响应代码。

The solution from my blog post (referenced in the OP) was based on an existing solution we were/are using to alter HTTP Response Codes during an error state.

所以，对我们来说，这是一个一行的改变，将异常传递给ELMAH。如果有更好的解决方案，我也很乐意知道。

So, for us it was a one-line change to pass the Exception to ELMAH. If there's a better solution, I'd love to know about it too.

对于后台/参考和潜在的改进 - 这里是当前解决方案的代码。

For Posterity/Reference, and potential improvement - here's the code from the current solution.

using System;
using System.ServiceModel;
using System.ServiceModel.Dispatcher;
using System.ServiceModel.Channels;
using System.ServiceModel.Description;
using System.Collections.ObjectModel;
using System.Net;
using System.Web;
using Elmah;
namespace YourApplication
{
    /// <summary>
    /// Your handler to actually tell ELMAH about the problem.
    /// </summary>
    public class HttpErrorHandler : IErrorHandler
    {
        public bool HandleError(Exception error)
        {
            return false;
        }

        public void ProvideFault(Exception error, MessageVersion version, ref Message fault)
        {
            if (error != null ) // Notify ELMAH of the exception.
            {
                if (System.Web.HttpContext.Current == null)
                    return;
                Elmah.ErrorSignal.FromCurrentContext().Raise(error);
            }
        }
    }
    /// <summary>
    /// So we can decorate Services with the [ServiceErrorBehaviour(typeof(HttpErrorHandler))]
    /// ...and errors reported to ELMAH
    /// </summary>
    public class ServiceErrorBehaviourAttribute : Attribute, IServiceBehavior
    {
        Type errorHandlerType;

        public ServiceErrorBehaviourAttribute(Type errorHandlerType)
        {
            this.errorHandlerType = errorHandlerType;
        }

        public void Validate(ServiceDescription description, ServiceHostBase serviceHostBase)
        {
        }

        public void AddBindingParameters(ServiceDescription description, ServiceHostBase serviceHostBase, Collection<ServiceEndpoint> endpoints, BindingParameterCollection parameters)
        {
        }

        public void ApplyDispatchBehavior(ServiceDescription description, ServiceHostBase serviceHostBase)
        {
            IErrorHandler errorHandler;
            errorHandler = (IErrorHandler)Activator.CreateInstance(errorHandlerType);
            foreach (ChannelDispatcherBase channelDispatcherBase in serviceHostBase.ChannelDispatchers)
            {
                ChannelDispatcher channelDispatcher = channelDispatcherBase as ChannelDispatcher;
                channelDispatcher.ErrorHandlers.Add(errorHandler);
            }
        }
    }
}

用法例如

使用ServiceErrorBehaviour属性装饰您的WCF服务：

Usage Example

Decorate your WCF Services with the ServiceErrorBehaviour Attribute:

[ServiceContract(Namespace = "http://example.com/api/v1.0/")]
[ServiceErrorBehaviour(typeof(HttpErrorHandler))]
public class MyServiceService
{
  // ...
}

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