future_plexer.rb

require 'celluloid'
 
class FuturePlexer
  class DrainedError < StandardError; end
 
  attr_accessor :futures
 
  def initialize(futures)
    self.futures = futures
  end
 
  def select(timeout = nil, &block)
    raise DrainedError, 'No futures left.' if drained?
 
    Celluloid.receive(timeout) do |msg|
      msg.is_a?(Celluloid::Future::Result) && futures.include?(msg.future)
    end
 
    results = []
    futures.each do |future|
      if future.ready?
        results << future.value
        futures.delete(future)
      end
    end
 
    if block_given?
      results.map(&block)
    else
      results
    end
  end
 
  def drained?
    futures.empty?
  end
end
 
class MyActor
  include Celluloid
  include Celluloid::Logger
 
  def initialize
    futures = 10.times.map do |i|
      future.work(i)
    end
 
    async.wait_for_tasks(futures)
  end
 
  def wait_for_tasks(futures)
    plexer = FuturePlexer.new(futures)
 
    until plexer.drained?
      begin
        plexer.select(0.150) do |result|
          info("A task finished: #{result}")
        end
      rescue Celluloid::TimeoutError
        info("Plexer doesn't have a result for us.")
      rescue FuturePlexer::DrainedError
        info("Plexer is already drained.")
      end
    end
 
    info("All tasks have finished.")
  end
 
  def work(i)
    time_to_work = (100 + rand(100)) / 1000.0
    info("Task #{i} is going to take #{time_to_work}s.")
    sleep(time_to_work)
    info("Task #{i} is ready.")
 
    i
  end
end
 
MyActor.new
sleep

output

$ bundle exec ruby future_plexer.rb
I, [2013-05-08T02:47:02.079739 #15586]  INFO -- : Task 0 is going to take 0.133s.
I, [2013-05-08T02:47:02.079994 #15586]  INFO -- : Task 1 is going to take 0.137s.
I, [2013-05-08T02:47:02.080098 #15586]  INFO -- : Task 2 is going to take 0.131s.
I, [2013-05-08T02:47:02.080207 #15586]  INFO -- : Task 3 is going to take 0.121s.
I, [2013-05-08T02:47:02.080303 #15586]  INFO -- : Task 4 is going to take 0.101s.
I, [2013-05-08T02:47:02.080434 #15586]  INFO -- : Task 5 is going to take 0.188s.
I, [2013-05-08T02:47:02.080572 #15586]  INFO -- : Task 6 is going to take 0.122s.
I, [2013-05-08T02:47:02.080712 #15586]  INFO -- : Task 7 is going to take 0.157s.
I, [2013-05-08T02:47:02.081376 #15586]  INFO -- : Task 8 is going to take 0.176s.
I, [2013-05-08T02:47:02.081609 #15586]  INFO -- : Task 9 is going to take 0.114s.
I, [2013-05-08T02:47:02.181815 #15586]  INFO -- : Task 4 is ready.
I, [2013-05-08T02:47:02.197616 #15586]  INFO -- : Task 9 is ready.
I, [2013-05-08T02:47:02.201827 #15586]  INFO -- : Task 3 is ready.
I, [2013-05-08T02:47:02.201923 #15586]  INFO -- : Task 6 is ready.
I, [2013-05-08T02:47:02.212361 #15586]  INFO -- : Task 2 is ready.
I, [2013-05-08T02:47:02.212509 #15586]  INFO -- : Task 0 is ready.
I, [2013-05-08T02:47:02.217423 #15586]  INFO -- : Task 1 is ready.
I, [2013-05-08T02:47:02.232533 #15586]  INFO -- : A task finished: 0
I, [2013-05-08T02:47:02.232621 #15586]  INFO -- : A task finished: 2
I, [2013-05-08T02:47:02.232666 #15586]  INFO -- : A task finished: 4
I, [2013-05-08T02:47:02.232708 #15586]  INFO -- : A task finished: 6
I, [2013-05-08T02:47:02.232747 #15586]  INFO -- : A task finished: 9
I, [2013-05-08T02:47:02.238984 #15586]  INFO -- : Task 7 is ready.
I, [2013-05-08T02:47:02.257820 #15586]  INFO -- : Task 8 is ready.
I, [2013-05-08T02:47:02.269687 #15586]  INFO -- : Task 5 is ready.
I, [2013-05-08T02:47:02.383617 #15586]  INFO -- : A task finished: 1
I, [2013-05-08T02:47:02.383698 #15586]  INFO -- : A task finished: 5
I, [2013-05-08T02:47:02.383751 #15586]  INFO -- : A task finished: 8
I, [2013-05-08T02:47:02.534242 #15586]  INFO -- : A task finished: 3
I, [2013-05-08T02:47:02.685123 #15586]  INFO -- : A task finished: 7
I, [2013-05-08T02:47:02.685209 #15586]  INFO -- : All tasks have finished.