title: Connection to app pool dropping IIS
body: <p>I have a WCF service which is hosted in one of our environments and causing problems only in this environment. The service is dropping if the request takes longer than 5 minutes to execute. (I timed it)</p>
  
  <p>I enabled Trace logging for the WCF service and found nothing of interest in the generated <code>.svclog</code> files. There is nothing in the <code>EventViewer</code> also. I do notice that the <code>HTTPERR</code> file has some logs in it.</p>
  
  <p><code>httperr</code></p>
  
  <pre><code>2018-06-12 00:17:31 **.*.***.*** 40028 **.*.***.** 20601 - - - - - Timer_ConnectionIdle -
  2018-06-12 00:45:47 **.*.***.** 30947 **.*.***.** 20601 - - - - - Timer_ConnectionIdle -
  2018-06-12 00:47:57 **.*.***.** 53295 **.*.***.** 20601 - - - - - Timer_ConnectionIdle -
  2018-06-12 00:47:57 **.*.***.** 47352 **.*.***.** 20601 - - - - - Timer_ConnectionIdle -
  2018-06-12 00:59:44 **.*.***.** 25663 **.*.***.** 20601 - - - - - Timer_ConnectionIdle -
  2018-06-12 01:04:50 **.*.***.** 35450 **.*.***.** 20601 - - - - - Timer_ConnectionIdle -
  2018-06-12 01:07:40 **.*.***.** 48289 **.*.***.** 20601 - - - - - Timer_ConnectionIdle -
  2018-06-12 01:19:36 **.*.***.*** 62695 *.*.***.** 20601 - - - - - Timer_ConnectionIdle -
  2018-06-12 01:20:56 **.*.***.*** 57339 *.*.***.** 20601 - - - - - Timer_ConnectionIdle -
  2018-06-12 01:26:46 **.*.***.*** 42058 *.*.***.** 20601 - - - - - Timer_ConnectionIdle -
  2018-06-12 02:14:52 **.*.***.*** 59815 *.*.***.** 20601 - - - - - Timer_ConnectionIdle -
  2018-06-12 02:38:12 **.*.***.*** 2487 *.*.***.* 20601 - - - - - Timer_ConnectionIdle -
  2018-06-12 06:14:37 **.*.***.*** 47072 *.*.***.** 80 - - - 400 - Verb -
  2018-06-12 13:03:52 **.*.***.** 23883 *.*.*.** 20601 - - - - - Timer_ConnectionIdle -
  2018-06-12 13:08:47 **.*.***.** 32002 *.*.*.** 20601 HTTP/1.1 POST /SomeUrl/SomeService.svc - 2 Connection_Dropped Foo-SomeService-AppPool
  2018-06-12 13:32:22 **.*.***.** 45018 *.*.*.** 20601 HTTP/1.1 POST /SomeUrl/SomeService.svc - 2 Connection_Dropped Foo-SomeService-AppPool
  </code></pre>
  
  <p>I checked the <code>Timer_ConnectionIdle</code> <a href="https://msdn.microsoft.com/en-us/library/windows/desktop/aa364693(v=vs.85).aspx" rel="nofollow noreferrer">docs</a> and increased the <code>Connection Timeout</code> setting within the site in IIS, but the same happened. (Increased it from <code>120</code> to <code>240</code>). What's strange about the <code>httperr</code> file which I don't understand is the <code>DateTime</code> field. The <code>Timer_ConnectionIdle</code> starts at <code>00:17:31</code>, but it should have dropped them earlier than <code>13:08:47</code>.</p>
  
  <p>The <code>Connection_Dropped</code> from the <a href="https://msdn.microsoft.com/en-us/library/windows/desktop/aa364693(v=vs.85).aspx" rel="nofollow noreferrer">docs</a> means:</p>
  
  <blockquote>
    <p>IIS failed to return the logging data within the specified time limit (1 minute) due to a client disconnect (or reset) before the response was logged. </p>
  </blockquote>
  
  <p>So the connection was dropped before IIS even got a chance to log why it dropped. What else can be causing the <code>Connection_Dropped</code> from the app pool?</p>