Practical EventMachine

EventMachine (EM) is an event-driven concurrency library for Ruby, akin to Python's Twisted or Node.js. In this talk we'll explore some of the patterns and abstractions behind EM, how we can apply those ideas to our applications and how the library has been used by companies like GitHub and Heroku.

Transcript

1. Practical EventMachine
2. @febuiles
3. http://goo.gl/Oqe4SI
4. Events events
5. $("#door").on("open", function(){ log("We got a new Joe in town..."); });
6. WHY EVENTS?
7. i/o
8. latency
9. MOST APPLICATIONS ARE I/O BOUND I/O BOUND
10. https://github.com/blog/517-unicorn YOUR TYPICAL CONCURRENCY MODEL
11. server = TCPServer.new(1337) ! while client = server.accept message = client.readline client.write "> #{message}" client.close end
12. server = TCPServer.new(1337) ! while true Thread.new(server.accept) do |client| message = client.readline client.write "> #{message}" client.close end end
13. THE REACTOR
14. What is a reactor?
15. while true events.each do |event| event.process end end
16. Chernobyl, 1986
17. New Safe Confinement (NSC)
18. DON’T BLOCK THE REACTOR
19. Reactor.run { on(:receive) do |msg| return if invalid_message(msg)? ! device = Device.find(msg.device_id) device.update(position: msg.position) end }
20. Reactor.run { on(:receive) do |msg| return if invalid_message(msg)? ! device = Device.find(msg.device_id) device.update(position: msg.position) end }
21. What is EventMachine?
22. EventMachine is an event-driven I/O and lightweight concurrency library for Ruby.
23. ?
24. EventMachine is a fast, simple event- processing library for Ruby programs
25. A PIMPED REACTOR.
26. Why EventMachine?
27. EventMachine is dead.
29. EventMachine is dead EventMachine is stable.
30. Heroku Thin Campfire GitHub Rainbows EngineYard
31. module Echo def receive_data(message) send_data "> #{message}" end end ! EM.run { EM.start_server "0.0.0.0", 1337, Echo }
32. module Echo def post_init puts "Client connected" end ! def receive_data(message) send_data "> #{message}" end ! def unbind puts "Client disconnected" end end ! EM.run { EM.start_server "0.0.0.0", 1337, Echo }
33. EM HANDLERS VS CALLBACK HELL
34. server = AsyncTCPServer.new("0.0.0.0", 1337) ! server.on(:accept) { message = client.async_read ! message.on(:ready) { client.write "> #{message}" client.close } } ! server.on(:connect) { puts "Client connected" } ! server.on(:disconnect) { puts "Client disconnected" }
35. events
 post_init connection_completed receive_data
 unbind ssl_handshake_completed methods start_tls get_peername
 send_data
 close_connection close_connection_after_writing proxy_incoming_to pause/resume
36. Mixing Paradigms
37. module Echo def receive_data(data) message = parse_data(data) return if invalid_message(message)? ! device = Device.find(message.device_id) device.update(position: message.position) send_data :updated end end ! EM.run { EM.start_server "0.0.0.0", 1337, Echo }
38. module Echo def receive_data(data) message = parse_data(data) return if invalid_message(message)? ! device = Device.find(message.device_id) device.update(position: message.position) send_data :updated end end ! EM.run { EM.start_server "0.0.0.0", 1337, Echo }
39. DON’T BLOCK THE REACTOR
41. DATA STORES ! cassandra couchdb memcached mongodb mysql postgresql redis
42. HTTP ! HttpRequest Faraday
43. PROTOCOLS ! tcp udp amqp smtp stomp xmpp dns websockets and more…
44. Other ! EM.popen EM.defer
45. module Graham def receive_data(number) calculate = proc { graham(number) } ! report = proc { |result| send_data(result) } ! EM.defer(calculate, report) end end
46. EM API
47. EM API ! EM::timer EM::deferrable EM::queue EM::channel EM.watch_file EM.watch_process
48. Closing Thoughts
49. Events are hard.
50. Evented Programming for Evented Problems
51. DON’T BLOCK THE REACTOR !!1
52. Thanks :) ! http://mheroin.com/rubyconfar @febuiles
53. Credits Federico’s illustration: Pablo Pérez Nuclear cooling tower: Jonathan Brennan Some code samples: Aman Gupta & Jeremy Cheung Unicorn diagram: GitHub The rest: Wikipedia