Accessing EventMachine internal queues -- when working with defer ...

em-expose-queues.rb

module EventMachine
  def self.threadqueue
    @threadqueue
  end

  def self.resultqueue
    @resultqueue
  end
end

EventMachine.run do
  EventMachine.threadpool_size = 1

  EM.add_periodic_timer(1) do
    p [EventMachine.threadqueue.size,
       EventMachine.resultqueue.size,
       EventMachine.threadqueue.num_waiting]
  end
  
  4.times do
    EventMachine.defer(Proc.new { sleep 5 }, Proc.new { p 'DONE' })
  end
end