[Mono-list] HttpWebRequest.GetResponse() can trigger an uncatchable exception

[James Wright]

   Is there a possibility this error is caused by the client dropping 
the connection before sending the full request, rather than heavy load?

James

On 10/07/2011 10:31, Christopher David Howie wrote:
>   On Sat, 9 Jul 2011 11:50:34 -0400, Gonzalo Paniagua Javier wrote:
>> Not much I can do without a test case.
>   I know.  :(  The worst bug is the one that only happens once in a blue
>   moon.
>
>> I'd say that this is a problem reusing a connection and somehow 2
>> threads "own" the same stream. Set KeepAlive to false (and increase
>> the number of file descriptors! (ulimit)) and see if you can still
>> reproduce the problem. If it does not happen, bingo! Reduce the
>> 'maxconnections' setting via app.config file to 1 and begin as many
>> requests as possible to the same URL. If you can reproduce it this
>> way, it's easier to find when 2 threads are using the same stream.
>   I'm using the following code:
>
>   ---------->8----------
>   using System;
>   using System.Linq;
>   using System.Net;
>   using System.Threading;
>
>   internal class Program
>   {
>       private static string url;
>
>       private const int THREAD_COUNT = 1000;
>
>       private static void Main(string[] args)
>       {
>           ServicePointManager.DefaultConnectionLimit = 1;
>
>           url = args.Length>  0 ? args[0] : "http://localhost/";
>
>           var threads = new Thread[THREAD_COUNT];
>
>           for (int i = 0; i<  THREAD_COUNT; i++) {
>               threads[i] = new Thread(WorkerThread);
>               threads[i].Start();
>           }
>
>           for (int i = 0; i<  THREAD_COUNT; i++) {
>               threads[i].Join();
>           }
>       }
>
>       private static void WorkerThread()
>       {
>           for (;;) {
>               var request = (HttpWebRequest)WebRequest.Create(url);
>               request.KeepAlive = false;
>
>               try {
>                   using (request.GetResponse())
>                       Console.Write('.');
>               } catch {
>                   Console.Write('!');
>               }
>           }
>       }
>   }
>   ---------->8----------
>
>   So far (10+ minutes) no exception has been thrown by this test.  I'd be
>   open to suggestions on how to tweak it.
>
>> Also check the values of the variables involved in that BlockCopy
>> call
>> and the values of readBuffer* before the call.
>   I know that readBufferOffset is -1.  I'm not sure about the others.  If
>   we can get a consistent repro then I'll be able to check pretty easily.
>