Don't log errors when client aborts the connection

[danroth27]

Currently when you run the web command for the default ASP.NET 5 Web Site template you see errors whenever the client aborts the connection (ex you cancel the browser request). Clients aborting the connection is really an expected behavior and should not be logged as a server error.

Repro steps:

• Create a new ASP.NET 5 Web Site
• Switch to the web command and ctrl-F5
• Browse to localhost:5000 but then cancel the request
• A red error message with an IOException stack trace is displayed in the console output window

Started
error   : [Microsoft.AspNet.Server.WebListener.MessagePump] ProcessRequestAsync
System.IO.IOException ---> Microsoft.Net.Http.Server.WebListenerException: The s
pecified network name is no longer available
   --- End of inner exception stack trace ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNot
ification(Task task)
   at Microsoft.AspNet.StaticFiles.StaticFileContext.<SendAsync>d__42.MoveNext()

--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNot
ification(Task task)
   at Microsoft.AspNet.Diagnostics.Entity.DatabaseErrorPageMiddleware.<Invoke>d_
_6.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.AspNet.Diagnostics.Entity.DatabaseErrorPageMiddleware.<Invoke>d_
_6.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNot
ification(Task task)
   at Microsoft.AspNet.Diagnostics.ErrorPageMiddleware.<Invoke>d__4.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.AspNet.Diagnostics.ErrorPageMiddleware.<Invoke>d__4.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNot
ification(Task task)
   at Microsoft.VisualStudio.Web.BrowserLink.Runtime.BrowserLinkMiddleware.<Exec
uteWithFilter>d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNot
ification(Task task)
   at Microsoft.AspNet.Hosting.Internal.RequestServicesContainerMiddleware.<Invo
ke>d__3.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNot
ification(Task task)
   at Microsoft.AspNet.Server.WebListener.MessagePump.<ProcessRequestAsync>d__19
.MoveNext()

[davidfowl]

+1

[Tratcher]

Warning?

[davidfowl]

Debug

[Tratcher]

For reference, this catch statement and logger are at the root of the request processing call-stack. You end up here if anything goes wrong during a request. At this point we will rarely know the cause of the exception.

Are you recommending we suppress logging all exceptions if we think the client has disconnected? That's why I recommended Warning.

[Tratcher]

http://stackoverflow.com/questions/33143918/weblistenerexceptionthe-specified-network-name-is-no-longer-available

[Tratcher]

The stack trace is a little different now that WebListener has some buffering enabled by default:

01:29:55.8657 Error Flush
System.IO.IOException ---> Microsoft.Net.Http.Server.WebListenerException: The specified network name is no longer available
   --- End of inner exception stack trace ---
01:29:55.8901 Error ProcessRequestAsync
System.IO.IOException ---> Microsoft.Net.Http.Server.WebListenerException: The specified network name is no longer available
   --- End of inner exception stack trace ---
   at Microsoft.Net.Http.Server.ResponseStream.FlushInternal(Boolean endOfRequest)
   at Microsoft.Net.Http.Server.ResponseStream.Dispose(Boolean disposing)
   at System.IO.Stream.Close()
   at Microsoft.Net.Http.Server.Response.Dispose()
   at Microsoft.Net.Http.Server.RequestContext.Dispose()
   at Microsoft.AspNet.Server.WebListener.MessagePump.<ProcessRequestAsync>d__23.MoveNext()

The error now commonly happens after app code when flushing the buffer. It will be easier to de-emphasize errors in this scenario.

[Tratcher]

Related: #173. If we suppress throwing write errors then we don't have to worry as much about logging them when caught later.

[Tratcher]

aspnet/StaticFiles#150

[Tratcher]

All the work in this repo has been completed. We'll work on StaticFiles separately.