Ruby/Threads/SizedQueue

require "thread"
buffer = SizedQueue.new(2)
producer = Thread.new do
  item = 0
  loop do
    sleep rand 0
    puts "Producer makes #{item}"
    buffer.enq item
    item += 1
  end
end
consumer = Thread.new do
  loop do
    sleep (rand 0)+0.9
    item = buffer.deq
    puts "Consumer retrieves #{item}"
    puts "  waiting = #{buffer.num_waiting}"
  end
end