code: def get_queue(value)
        ms = (Time.now.to_f * 1000).to_i - value.to_i
        ms < 0 ? 0 : ms
      end
docs: Calculates the difference, in milliseconds, between the
   HTTP_X_REQUEST_START time and the current time.
  
   @param [String] the timestamp from HTTP_X_REQUEST_START.
   @return [Integer] the queue time in milliseconds.