2010-02-09 Reactor Pattern & Event Driven Programming
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The document discusses the reactor pattern and event-driven programming. It explains that the reactor pattern uses an event loop to process I/O asynchronously without blocking. EventMachine is given as an example of a reactor implementation in Ruby. It also explains how the thin web server uses EventMachine and the reactor pattern to handle requests asynchronously by delegating I/O to EventMachine and processing requests with thin handlers.
![concurrency, why
and how in network
• [network I/O] is slow, we shouldn't wait for
[network I/O] while make [CPU] idle.](https://image.slidesharecdn.com/2010-02-09-reactor-pattern-and-100414013325-phpapp01/85/2010-02-09-Reactor-Pattern-Event-Driven-Programming-11-320.jpg)
![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.](https://image.slidesharecdn.com/2010-02-09-reactor-pattern-and-100414013325-phpapp01/85/2010-02-09-Reactor-Pattern-Event-Driven-Programming-12-320.jpg)
![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](https://image.slidesharecdn.com/2010-02-09-reactor-pattern-and-100414013325-phpapp01/85/2010-02-09-Reactor-Pattern-Event-Driven-Programming-13-320.jpg)
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2010-02-09 Reactor Pattern & Event Driven Programming
- 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/
- 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
- 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...... ?