Elmah Does not email in a fire and forget scenario

问题

I have a MVC app where I am trying to capture all the incoming requests in a ActionFilter. Here is the logging code. I am trying to log in a fire and forget model.

My issue is if I execute this code synchronously by taking out the Task.Run Elmah does send out an email. But for the code shown below I can see the error getting logged to the InMemory logger in elmah.axd but no emails.

public void Log(HttpContextBase context)
        {
             Task.Run(() =>
            {
                try
                {
                    throw new NotImplementedException(); //simulating an error condition
                    using (var s = _documentStore.OpenSession())
                    {
                        s.Store(GetDataToLog(context));
                        s.SaveChanges();
                    }

                }
                catch (Exception ex)
                {
                    ErrorSignal.FromCurrentContext().Raise(ex);
                }
            });
        }

回答1:

Got this answer from Atif Aziz (Elmah Lead contributor) on the ELMAH google group

When you use Task.Run, the HttpContext is not transferred to the thread pool thread on which your action will execute. When ErrorSignal.FromCurrentContext is called from within your action, my guess is that it's probably failing with another exception because there is no current context. That exception is lying with the Task. If you're on .NET 4, you're lucky because you'll see the ASP.NET app crash eventually (but possibly much after the fact) when the GC will kick in and collect the Task and its exception will go “unobserved”. If you're on .NET 4.5, the policy has been changed and the exception will simply get lost. Either way, your observation will be that mailing is not working. In fact, logging won't work either unless you use Elmah.ErrorLog.GetDefault(null).Log(new Error(ex)), where a null context is allowed. But that call only logs the error but does not do any mailing. ELMAH's modules are connected to the ASP.NET context. If you detach from that context by forking to another thread, then you cannot rely on ELMAH's modules. You can only use Elmah.ErrorLog.GetDefault(null).Log(new Error(ex)) reliably to log an error.

• Atif

来源：https://stackoverflow.com/questions/22237435/elmah-does-not-email-in-a-fire-and-forget-scenario