Asynchronous IO behaving synchronously using Ruby 1.9's fibers

async_io_looking_sync.rb

# this code snippet was inspired by
# http://www.igvita.com/2010/04/15/non-blocking-activerecord-rails/

require 'fiber' # needed to use Fiber.current
require 'rubygems'
require 'mysqlplus'
require 'eventmachine'
require 'em-mysqlplus'

def query(sql)
  con = EventMachine::MySQL.new(:host => 'localhost')
  f = Fiber.current
  r = con.query sql
  r.callback { |res|
    f.resume res
  }
  Fiber.yield
end

EM.run {
  count = 0
  3.times do
    Fiber.new {
      puts "Sending query..."
      result = query('SELECT SLEEP(1)')
      puts "Result: #{result}"
      count += 1
      EM.stop if count == 3
    }.resume
  end
}

rasmus-rnn-nielsens-macbook-pro:ruby rasmus$ time ruby mysql_test.rb
Sending query...
Sending query...
Sending query...
Result: #Mysql::Result:0x00000100ae38d0
Result: #Mysql::Result:0x00000100ae3748
Result: #Mysql::Result:0x00000100ae3630

real 0m1.054s
user 0m0.035s
sys 0m0.016s