thread_pool.rb

require 'thread'

QUEUE_SIZE = 2
POOL_SIZE  = 5

queue = SizedQueue.new(QUEUE_SIZE)

producers = POOL_SIZE.times.map do
  Thread.new do
    item = rand(10)
    queue.enq(item)
    puts "--> Enqueue #{item}"
  end
end

consumers = POOL_SIZE.times.map do
  Thread.new do
    begin
      while item = queue.deq(true)
        puts "--> Dequeue #{item}"
      end
    rescue ThreadError
    end
  end
end

producers.map(&:join)
consumers.map(&:join)

# --> Enqueue 6
# --> Enqueue 9
# --> Dequeue 6
# --> Dequeue 9
# --> Enqueue 0
# --> Enqueue 6
# --> Dequeue 0
# --> Dequeue 6
# --> Enqueue 6
# --> Dequeue 6