def _HandleFlowProcessingRequestLoop(self, handler):
    """Handler thread for the FlowProcessingRequest queue."""
    while not self.flow_handler_stop:
      with self.lock:
        todo = self._GetFlowRequestsReadyForProcessing()
        for request in todo:
          self.flow_handler_num_being_processed += 1
          del self.flow_processing_requests[(request.client_id,
                                             request.flow_id)]

      for request in todo:
        handler(request)
        with self.lock:
          self.flow_handler_num_being_processed -= 1

      time.sleep(0.2)