t.rb

require 'thread'


class WorkerPool

  def initialize
    @num = 10
    @jobs = Queue.new
    @results = Queue.new
    @stopped = false
    run
  end

  def <<(j)
    @jobs << j
  end

  def run
    @threads = @num.times.map do
      Thread.new do
        loop do
          break if @stopped && @jobs.empty?
          @results << @jobs.pop.call
        end
      end
    end
  end

  def stop
    @stopped = true
    @threads.each{|t| t.run if t.alive? }
  end

  def join
    @threads.each(&:join)
  end

  def value
    join
    @results
  end

end

w = WorkerPool.new
rand(100).times{ w << ->{ sleep rand } }
w.stop
r = w.value
p r.pop until r.empty?