test multi-threaded concurrency with activerecord adapters

gistfile1.rb

# Adapted from slide 5 at http://www.slideshare.net/igrigorik/no-callbacks-no-threads-railsconf-2010

require 'rubygems'
require 'active_record'
require 'mysql'

gem 'mysql2', "< 0.3.0" # for rails 3.0
#gem 'mysql2', ">= 0.3.0" # for rails 3.1

ActiveRecord::Base.establish_connection(
  :adapter => 'mysql2', # or 'mysql' 
  :host => '',
  :database => '',
  :username => '',
  :password => '',
  :pool => 5
)

stime = Time.now

threads = []
10.times do |n|
  threads << Thread.new do 
    ActiveRecord::Base.connection_pool.with_connection do |conn|
      res = conn.execute("sqlite3_sleep(1000)")
    end
  end
end

  
threads.each do |t|
  begin
    t.join
  rescue Exception => e
    puts "Exception in thread: #{e.class}"
  end
end

puts "\n\nElapsed real time: #{Time.now - stime} seconds"

# On my computer:
#
# * mysql:  10.19 seconds, as expected for broken mysql adapter that holds onto
#   ruby GIL 
#
# * mysql2 with either ruby 1.8.7 OR ruby 1.9.2: 2.1 seconds 
#   (still surprisingly more than the 1s and change expected. still a lot of 
#    overhead from  context switching and/or connection pool checkout? 
#    But not as disastrous as 'mysql'