From: Douglas Seifert <doug@...>
Date: 2009-09-04T10:55:25+09:00
Subject: Re: Threads - running something in background

7stud's original Updater class seems to meet the requirements.  Are
you trying to write a class that will perform some work and then sleep
1.0 seconds and keep a count of the number of iterations it performed?
 Or are you trying to right a class that will perform some work
exactly once per second?  In the first case, your work will not
generally fire once a second because the work itself will take a non
zero amount of time.  The second case is trickier ... maybe this would
work:

class PeriodicWorker
  def initialize(period = 1.0)
    @period = period
  end

  def run
    start = Time.now.to_f
    while true
      yield
      sleep_time = (start + @period) - Time.now.to_f
      sleep(sleep_time) rescue nil # Punt if the worker took longer
than @period seconds to run
      start += @period
    end
  end
end

worker = PeriodicWorker.new

worker.run do
 puts "Time: #{Time.now.to_f}"
 sleep 0.22
 puts "Finished my work: #{Time.now.to_f}"
end


The only issue with this class is if the work takes longer than the
period, you are creating a spinloop that will suck up 100% of your
CPU.

-Doug Seifert