gistfile1.rb

to_parse = Queue.new
to_fetch = Queue.new

threads = []

threads << Thread.new do
  while true do
    if queue.size > MAX_WE_WANT_QUEUED
      sleep 5
    else
      to_parse << get_the_file_to_parse
    end
  end
end

threads << Thread.new do
  to_fetch << result_of_parsing(to_parse.deq)
end

threads.concat (1..20).map do |i|
  Thread.new do
    download_file(to_fetch.deq)
  end
end

threads.each {|t| t.join }