[Mono-bugs] [Bug 78365][Min] New - HttpListener misses its requests

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Changed by pawel.sakowski at mind-breeze.com.

http://bugzilla.ximian.com/show_bug.cgi?id=78365

--- shadow/78365	2006-05-11 03:24:14.000000000 -0400
+++ shadow/78365.tmp.17419	2006-05-11 03:24:14.000000000 -0400
@@ -0,0 +1,139 @@
+Bug#: 78365
+Product: Mono: Class Libraries
+Version: 1.1
+OS: GNU/Linux [Other]
+OS Details: 
+Status: NEW   
+Resolution: 
+Severity: 
+Priority: Minor
+Component: System
+AssignedTo: mono-bugs at ximian.com                            
+ReportedBy: pawel.sakowski at mind-breeze.com               
+QAContact: mono-bugs at ximian.com
+TargetMilestone: ---
+URL: 
+Cc: 
+Summary: HttpListener misses its requests
+
+Description of Problem:
+When put under a stress load, the HttpListener randomly fails to answer
+some HTTP requests, eventually leading to a client timeout.
+
+Steps to reproduce the problem:
+1. Compile the server:
+using System;
+using System.IO;
+using System.Net;
+using System.Threading;
+
+class Server
+{
+  static void Main()
+  {
+
+    HttpListener l = new HttpListener();
+    l.Prefixes.Add("http://*:8765/");
+    l.Start();
+
+    while (true)
+    {
+      HttpListenerContext ctx = l.GetContext();
+      new Thread(handle).Start(ctx);
+    }
+
+  }
+  static byte[] buf = new byte[20000];
+  static void handle(object o)
+  {
+
+    HttpListenerContext ctx = (HttpListenerContext)o;
+    Stream stream = ctx.Request.InputStream;
+    stream.Read(buf, 0, buf.Length);
+    stream.Close();
+    HttpListenerResponse r = ctx.Response;
+    r.StatusCode = 200;
+    r.ContentLength64 = 0;
+    Stream outputStream = r.OutputStream;
+    outputStream.Write(buf, 0, 0);
+    outputStream.Close();
+    r.Close();
+
+  }
+}
+
+2. Compile the client:
+using System;
+using System.Net;
+using System.IO;
+using System.Threading;
+public class Client
+{
+  static void Main()
+  {
+    for (uint i = 0; i < 10; i++)
+    {
+      new Thread(go).Start();
+    }
+    go();
+  }
+  static void go()
+  {
+    Uri uri = new Uri("http://127.0.0.1:8765");
+    byte[] buf = new byte[10039 + 12];
+    int length = 200;
+    uint seq = 0;
+    Array.Copy(BitConverter.GetBytes(Thread.CurrentThread.ManagedThreadId),
+buf, 4);
+    while (true)
+    {
+      try
+      {
+        Array.Copy(BitConverter.GetBytes(seq), 0, buf, 8, 4);
+        WebRequest req = WebRequest.CreateDefault(uri);
+        req.Method = "POST";
+        req.ContentLength = length;
+        Stream stream = req.GetRequestStream();
+        stream.Write(buf, 0, length);
+        stream.Close();
+        WebResponse response = req.GetResponse();
+        response.Close();
+        length = 12 + ((length - 12) + 103) % (buf.Length - 12);
+        seq++;
+      }
+      catch (Exception ex)
+      {
+        Console.WriteLine("Thread " +
+Thread.CurrentThread.ManagedThreadId.ToString("x") + " seq " + seq + ": " +
+ex);
+      }
+    }
+  }
+}
+
+3. Invoke both.
+4. Wait about 30 minutes.
+
+Actual Results:
+Thread b6efdbb0 seq 13660: System.Net.WebException: The request timed out
+in <0x000bf> System.Net.HttpWebRequest:GetRequestStream ()
+in <0x00121> Client:go ()
+[several times, the numbers obviously vary]
+
+Expected Results:
+No exception thrown over an arbitrary time period.
+
+How often does this happen? 
+Virtually always reproduces in under 1 hour.
+
+Additional Information:
+Ad-hoc locking in HttpListener.cs leads to a race condition. If a new
+request arrives while BeginGetContext gets after the "lock (ctx_queue)"
+line, but before the "lock (wait_queue)" line:
+
+- RegisterContext adds the new HttpListenerContext to ctx_queue,
+- BeginGetContext adds the ListenerAsyncResult to wait_queue,
+- the two never meet.
+
+Theoretically at any point at least one of the queues should be empty; this
+condition is violated in the above situation.