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  • 1. Reactor Pattern & Event-Driven Programming A scalable concurrent approach, using EventMachine with Thin as an example Lin Jen-Shin, http://godfat.org/
  • 2. Reactor Pattern & Event-Driven Programming http://godfat.org/slide/2010-02-29-reactor-pattern-and.pdf Lin Jen-Shin, http://godfat.org/
  • 3. Table of Contents
  • 4. Table of Contents • concurrency, why and how in network
  • 5. Table of Contents • concurrency, why and how in network • Event-Driven Programming explained in Flash with Ruby syntax
  • 6. Table of Contents • concurrency, why and how in network • Event-Driven Programming explained in Flash with Ruby syntax • Reactor Pattern in EventMachine with Thin
  • 7. Table of Contents • concurrency, why and how in network • Event-Driven Programming explained in Flash with Ruby syntax • Reactor Pattern in EventMachine with Thin • how Thin works
  • 8. Table of Contents • concurrency, why and how in network • Event-Driven Programming explained in Flash with Ruby syntax • Reactor Pattern in EventMachine with Thin • how Thin works • how EventMachine works
  • 9. Table of Contents • concurrency, why and how in network • Event-Driven Programming explained in Flash with Ruby syntax • Reactor Pattern in EventMachine with Thin • how Thin works • how EventMachine works
  • 10. concurrency, why and how in network
  • 11. concurrency, why and how in network • [network I/O] is slow, we shouldn't wait for [network I/O] while make [CPU] idle.
  • 12. concurrency, why and how in network • [network I/O] is slow, we shouldn't wait for [network I/O] while make [CPU] idle. • you can replace [network I/O] and [CPU] with all other resources like [disc I/O], [memory I/O], etc.
  • 13. concurrency, why and how in network • [network I/O] is slow, we shouldn't wait for [network I/O] while make [CPU] idle. • you can replace [network I/O] and [CPU] with all other resources like [disc I/O], [memory I/O], etc. • each kernel process/thread for each client using a blocking I/O is easy to write but not scalable at all
  • 14. Table of Contents • concurrency, why and how in network • Event-Driven Programming explained in Flash with Ruby syntax • Reactor Pattern in EventMachine with Thin • how Thin works • how EventMachine works
  • 15. Event-Driven Programming to the rescue
  • 16. Event-Driven Programming • only one process/thread
  • 17. Event-Driven Programming • only one process/thread • inversion of control
  • 18. Event-Driven Programming • only one process/thread • inversion of control • consists of an event loop and various event handlers
  • 19. Event-Driven Programming • inversion of control
  • 20. Event-Driven Programming loop{ # you control the flow do_something } • inversion of control
  • 21. Event-Driven Programming register method(:do_something) loop{ loop{ # you control the flow # event loop control the flow, do_something # later it calls your callback } event = pop_event_queue • inversion of control dispatch event if event }
  • 22. Event-Driven Programming register method(:do_something) loop{ # event loop control the flow, # later it calls your callback event = pop_event_queue dispatch event if event } • consists of an event loop and various event handlers
  • 23. Event-Driven Programming register method(:do_something) loop{ # event loop control the flow, # later it calls your callback event = pop_event_queue dispatch event if event } • consists of an event loop and various event handlers
  • 24. Event-Driven Programming register method(:do_something) loop{ # event loop control the flow, # later it calls your callback event = pop_event_queue dispatch event if event } • consists of an event loop and various event handlers
  • 25. Event-Driven Programming in Flash with Ruby syntax
  • 26. Event-Driven Programming in Flash with Ruby syntax • game loop, an example of event loop
  • 27. Event-Driven Programming in Flash with Ruby syntax • game loop, an example of event loop • Flash ActionScript, onEnterFrame
  • 28. Event-Driven Programming in Flash with Ruby syntax • game loop, an example of event loop • Flash ActionScript, onEnterFrame • frame by frame
  • 29. Event-Driven Programming in Flash with Ruby syntax # in each sprite thread 30.times{ application.draw sprite sprite.x += 1 }
  • 30. sprite.onEnterFrame = lambda{ sprite.x += 1 } # in each sprite thread 30.times{ application.draw sprite sprite.x += 1 }
  • 31. sprite.onEnterFrame = lambda{ sprite.x += 1 } application.register sprite 30.times{ # event loop, also called game loop events = application.pop_event_queue events.each{ |event| application.dispatch event } # model/view separation application.draw application.sprites } # in each sprite thread 30.times{ application.draw sprite sprite.x += 1 }
  • 32. Table of Contents • concurrency, why and how in network • Event-Driven Programming explained in Flash with Ruby syntax • Reactor Pattern in EventMachine with Thin • how Thin works • how EventMachine works
  • 33. Reactor Pattern
  • 34. Reactor Pattern loop{ data = read handle data }
  • 35. Reactor Pattern register method(:handle) loop{ loop{ data = read data = partial_read handle data event = process data } dispatch event if event }
  • 36. Event-Driven Programming register method(:do_something) loop{ loop{ # you control the flow # event loop control the flow, do_something # later it calls your callback } event = pop_event_queue dispatch event if event }
  • 37. Reactor Pattern register method(:handle) loop{ loop{ data = read data = partial_read handle data event = process data } dispatch event if event }
  • 38. Reactor Pattern by wikipedia
  • 39. Reactor Pattern • resources # e.g. network I/O by wikipedia
  • 40. Reactor Pattern • resources # e.g. network I/O • synchronous event demultiplexer # i.e. the blocking event loop by wikipedia
  • 41. Reactor Pattern • resources # e.g. network I/O • synchronous event demultiplexer # i.e. the blocking event loop • dispatcher # i.e. handler manager and event dispatcher by wikipedia
  • 42. Reactor Pattern • resources # e.g. network I/O • synchronous event demultiplexer # i.e. the blocking event loop • dispatcher # i.e. handler manager and event dispatcher • request handler # e.g. thin handler by wikipedia
  • 43. Reactor Pattern Request (resource)
  • 44. Reactor Pattern EventMachine Request (demultiplexer (resource) + dispatcher)
  • 45. Reactor Pattern EventMachine Request Thin (or AMQP) (demultiplexer (resource) (request handler) + dispatcher)
  • 46. Reactor Pattern EventMachine Request Thin (or AMQP) (demultiplexer (resource) (request handler) + dispatcher) Rack Thin handler
  • 47. Reactor Pattern EventMachine Request Thin (or AMQP) (demultiplexer (resource) (request handler) + dispatcher) Rack Rails Rack Thin rack env adapter handler
  • 48. Reactor Pattern EventMachine Request Thin (or AMQP) (demultiplexer (resource) (request handler) + dispatcher) Rack Rails Rack Thin Rails rack env adapter handler
  • 49. your rails application Reactor Pattern EventMachine Request Thin (or AMQP) (demultiplexer (resource) (request handler) + dispatcher) Rack Rails Rack Thin Rails rack env adapter handler
  • 50. Reactor Pattern EventMachine is a generic network I/O server/client library due to I/O and request handler separation in Reactor Pattern
  • 51. Reactor Pattern • EventMachine (Ruby)
  • 52. Reactor Pattern • EventMachine (Ruby) • Twisted (Python)
  • 53. Reactor Pattern • EventMachine (Ruby) • Twisted (Python) • nodejs (JavaScript in V8)
  • 54. Reactor Pattern • EventMachine (Ruby) • Twisted (Python) • nodejs (JavaScript in V8) • libevent and libev (C)
  • 55. Reactor Pattern • select (POSIX)
  • 56. Reactor Pattern • select (POSIX) • poll (POSIX)
  • 57. Reactor Pattern • select (POSIX) • poll (POSIX) • epoll (Linux)
  • 58. Reactor Pattern • select (POSIX) • poll (POSIX) • epoll (Linux) • kqueue (BSD, Mac OS X (Darwin))
  • 59. Table of Contents • concurrency, why and how in network • Event-Driven Programming explained in Flash with Ruby syntax • Reactor Pattern in EventMachine with Thin • how Thin works • how EventMachine works
  • 60. how Thin works • Thin::Server
  • 61. how Thin works • Thin::Server • Thin::Backends::TcpServer # communicate with EventMachine
  • 62. how Thin works • Thin::Server • Thin::Backends::TcpServer # communicate with EventMachine • Thin::Connection # EventMachine event handler
  • 63. how Thin works • Thin::Server • Thin::Backends::TcpServer # communicate with EventMachine • Thin::Connection # EventMachine event handler • Thin::Request # partial HTTP request parsing # Rack env builder
  • 64. how Thin works Sorry! To be continued......
  • 65. how Thin works Sorry! To be continued...... ?