Class: QuartzTorrent::Rate

Inherits:
Object
  • Object
show all
Defined in:
lib/quartz_torrent/rate.rb

Overview

Class that keeps track of a rate, for example a download or upload rate. The class is used by calling ‘update’ with samples (numbers) representing the amount of units being measured accrued since the last call, and value returns the rate in units/second.

This is implemented as an exponential moving average. The weight of the current sample is based on an exponention function of the time since the last sample. To reduce CPU usage, when update is called with a new sample the new average is not calculated immediately, but instead the samples are summed until 1 second has elapsed before recalculating the average.

Instance Method Summary collapse

Constructor Details

#initialize(avgPeriod = 4.0) ⇒ Rate

Create a new Rate that measures the rate using samples. avgPeriod specifies the duration over which the samples are averaged.



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# File 'lib/quartz_torrent/rate.rb', line 15

def initialize(avgPeriod = 4.0)
  reset
  @avgPeriod = avgPeriod.to_f
end

Instance Method Details

#reset ⇒ Object

Reset the rate to empty.



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# File 'lib/quartz_torrent/rate.rb', line 40

def reset
  @value = nil
  @time = Time.new
  @sum = 0.0
end

#update(sample) ⇒ Object

Update the rate by passing another sample (number) representing units accrued since the last call to update.



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# File 'lib/quartz_torrent/rate.rb', line 28

def update(sample)
  now = Time.new
  elapsed = now - @time
  @sum += sample
  if elapsed > 1.0
    @value = newValue elapsed, @sum/elapsed
    @time = now
    @sum = 0.0
  end
end

#value ⇒ Object

Get the current rate. If there are too few samples, 0 is returned.



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# File 'lib/quartz_torrent/rate.rb', line 21

def value
  update 0
  @value ? @value : 0.0
end