title: Workflow Service stops responding after 464 messages
body: <p>I am having a peculiar issue while executing workflows.<br>
  I have tried everything I could think of and now need ideas.  </p>
  
  <p>Here is my configuration:<br>
  1. A WF4 Workflow Service (xamlx) hosted in IIS 7 and uses net.msmq/netMsmqBinding for transport (MSMQ is transactional).<br>
  2. No Workflow Persistence is used.<br>
  3. I use a console app client to send messages to the workflow (each message creates new workflow).
  4. Each workflow looks like:   Wait for START message -> Wait for END message (I only send START messages).</p>
  
  <p>If I send 500 messages - 464 get processed correctly, but above that all messages go to the lock_* queue and then move to poison queue.
  I have inspected Debug, Analytic event logs, as well as messages and trace svclogs
  Here is most detailed message I get:</p>
  
  <blockquote>
    <p>System.TimeoutException, mscorlib,
    Version=4.0.0.0, Culture=neutral,
    PublicKeyToken=b77a5c561934e089The operation
    did not complete within the allotted timeout of 00:00:30. The time
    allotted to this operation may have been a portion of a longer
    timeout. at
    System.Runtime.AsyncResult.End[TAsyncResult](IAsyncResult result) at
    System.ServiceModel.Activities.Dispatcher.PersistenceProviderDirectory.LoadOrCreateAsyncResult.HandleReserveThrottle(IAsyncResult
    result) at
    System.Runtime.AsyncResult.AsyncCompletionWrapperCallback(IAsyncResult
    result)System.TimeoutException: The
    operation did not complete within the allotted timeout of 00:00:30.
    The time allotted to this operation may have been a portion of a
    longer timeout. at
    System.Runtime.AsyncResult.End[TAsyncResult](IAsyncResult result) at
    System.ServiceModel.Activities.Dispatcher.PersistenceProviderDirectory.LoadOrCreateAsyncResult.HandleReserveThrottle(IAsyncResult
    result) at
    System.Runtime.AsyncResult.AsyncCompletionWrapperCallback(IAsyncResult
    result)</p>
  </blockquote>
  
  <p>at that point request to <code>http://localhost/MyWebService?wsdl</code> also fails with 404.</p>
  
  <p>If I restart IIS - everything goes back to normal until 464 messages are sent.</p>
  
  <ol>
  <li>Where can I find more detailed log? (I already have System.Diagnostics set to max verbosity)  </li>
  <li>Is number 464 magic at all?  </li>
  <li>What can be causing this web service locking up?</li>
  </ol>