em-requests.rb

require 'eventmachine'
require 'em-http'
require 'fiber'

def async_fetch(url)
  f = Fiber.current
  http = EventMachine::HttpRequest.new(url).get
  http.callback { f.resume(http) }
  return Fiber.yield
end

numbers = (1..25).to_a

t1 = Time.now

counter = 0

EventMachine.run do
  numbers.each do |number|
    Fiber.new{
      data = async_fetch("http://www.google.com/search?q=#{number}")
      counter += 1
      EventMachine.stop if counter == numbers.size
    }.resume
  end
end

puts (Time.now - t1).to_s

t2 = Time.now

counter = 0

EventMachine.run do
  numbers.each do |number|
    http = EventMachine::HttpRequest.new("http://www.google.com/search?q=#{number}").get
    http.callback do |data|
      counter += 1
      EventMachine.stop if counter == numbers.size
    end
  end
end

puts (Time.now - t2).to_s