/// <summary>
 /// Observes request state, updated aggregate metrics.
 /// </summary>
 /// <param name="requestState"></param>
 internal void ObserveRequestState(WebMetricsRequestState requestState)
 {
     lock (_lock)
     {
         _requestHandlerMillisecondsComposite.Increment(requestState.RequestHandlerMilliseconds);
         _requestMillisecondsComposite.Increment(requestState.RequestMilliseconds);
         _responseBodyLengthComposite.Increment(requestState.ResponseBodyLength);
         TotalObservedRequests.Increment();
     }
 }