slides from mwrc2009 lightning talk on EM: http://mwrc2009.confreaks.com/14-mar-2009-19-06-event-machine-aman-gupta.html

gistfile1.txt

require 'rubygems'
require 'eventmachine'

### EM::run takes over the process

# puts 1
# EM.run{
#   require 'mycode'
# }
# puts 3 # this will never happen


### timers and async blocks

# EM.run{
#   timer = EM::PeriodicTimer.new(0.25){
#     puts "#{Time.now}: hi!"
#   }
#   EM.add_timer(2){ timer.cancel }
# }


### long events block the reactor

# EM.run{
#   EM.add_periodic_timer(0.25){
#     puts "#{Time.now}: hi!"
#     sleep 1
#   }
# }


### the reactor is just a while loop

# while true
#  # fire timers
#  timers.each{ |t| t.fire if t.time <= Time.now }
# 
#  # check network i/o
#  select(sockets).each{ |fd|
#    fd.connection_completed if fd.connected?
#    fd.receive_data(fd.read) if fd.readable?
#    fd.unbind if fd.closed?
#  }
# 
#  # run threads
#  rb_thread_schedule() if threads.any?
# end


### using EM in your webapps

# require 'thin'
# 
# ## or, with mongrel/passenger
# 
# $em = Thread.new{ EM.run{} }
# %w(INT TERM).each{ |sig|
#   old=trap(sig){ EM.stop; old.call }
# }


### sending email

# email = EM::Protocols::SmtpClient.send(
#   :domain => 'mysite.com',
#   :host => 'mail.mysite.com',
#   :from => 'ruby@mysite.com',
#   :to => 'customer@gmail.com',
#   :content => 'hi'
# )
# email.callback { puts 'sent the email!' }
# email.errback  { puts 'email failed!'   }


### http requests

# require 'em-http'
# http = EM::HttpRequest.new('http://twitter.com/statuses/update.xml')
# req = http.post(
#   :head => {'Authorization' => ['user', 'pass']},
#   :body => 'status=hello world'
# )
# req.errback{ puts 'failed posting to twitter' }
# req.callback{ |http|
#   http.response_header.status
#   http.response
# }


### running external processes

# EM.system("convert -resize 50x50 huge.png thumb.png"){ |output, status|
#   if status.exitstatus == 0
#     # ...
#   end
# }


### slow mysql queries

# require 'em/mysql'
# mysql = EventedMysql.connect(...)
# mysql.select('select sleep(15) as num'){ |res|
#   res.first['num']
# }


### message queues

# require 'mq'
# AMQP.start(:host => 'localhost'){
#   MQ.queue('logging').subscribe{ |logmsg|
#     puts logmsg
#   }
# }


### custom servers

# module MyServer
#   def post_init
#     puts "--- someone connected!"
#   end
#   def receive_data data
#     puts "--- someone sent me data: #{data}"
#   end
#   def unbind
#     puts "--- someone disconnected!"
#   end
# end
# 
# EM.start_server '127.0.0.1', 8080, MyServer


### other features

# - udp servers/clients
# - ssl connections and certificate handling
# - epoll/kqueue for c10k scalability
# - platform compatibility
#   - java version for jruby
#   - C extension for 1.8 and 1.9
#   - pure ruby reactor for everything else


### eventmachine resources

# Homepage::       http://rubyeventmachine.com
# Rubyforge Page:: http://rubyforge.org/projects/eventmachine
# Google Group::   http://groups.google.com/group/eventmachine
# Mailing List::   http://rubyforge.org/pipermail/eventmachine-talk
# RDoc::           http://eventmachine.rubyforge.org
# IRC::            #eventmachine on irc.freenode.net