def monitor_system
      @monitor_thread = Thread.new do
        loop do
          was_overloaded = @overloaded
          @overloaded = overloaded?
          check_in if was_overloaded && !@overloaded
          sleep MONITOR_INTERVAL
        end
      end
    end
def monitor_system
      @monitor_thread = Thread.new do
        loop do
          was_overloaded = @overloaded
          @overloaded = overloaded?
          check_in if was_overloaded && !@overloaded
          sleep MONITOR_INTERVAL
        end
      end
    end
Launch a monitoring thread that periodically checks the node's load
 average and the amount of free memory remaining. If we transition out of
 the overloaded state, let central know.