code: @Override
  	public void process(Request request, Response response)
  	{
  		Long duration = computeDurationMillis(START_TIMES_BY_CORRELATION_ID.get(request.getCorrelationId()));
  		
  		if (duration != null && duration.longValue() > 0)
  		{
  			response.addHeader("X-Response-Time", String.valueOf(duration));
  		}
  	}
docs: Set the 'X-Response-Time' header to the response time in milliseconds.