Asynchronous Event-driven Architecture - The Twisted Way

This talk is aimed at explaining the event-driven architecture and asynchronous model, the reactor-pattern, and the basic concepts that make understanding and writing Twisted programs easier, and less abstruse and esoteric.

Picking up clues from the numerous attempts in the past to demystify the popular beliefs about the occult nature of Twisted, the talk is designed to help you acquire the “mental model” required to write and comprehend asynchronous code. We will start by developing a basic understanding of the synchronous, threaded, and asynchronous models, then move on to comparing and contrasting the former two with the latter.

Further, we will try and understand the philosophy and motivation behind the asynchronous event-driven model, and discuss the Twisted reactor and event-loop architecture. Finally, we'll try to contemplate and demystify "The Twisted Way" of doing things bolstered by excerpts from Tao Te Ching and The Tao of Programming.

Transcript

1. The Twisted Way
   - Ashwini Oruganti
   @_ashfall_
   PyCon Ireland 2013
   

   View Slide

2. Twisted
   asynchronous event-driven
   networking framework
   

   View Slide

3. Twisted
   asynchronous event-driven
   networking framework
   aka... HARD
   

   View Slide

4. The Need
   Twisted Reality: The Game
   Threads and Java
   The sadness
   

   View Slide

5. The Beginning
   select()
   asyncore and Medusa
   …
   

   View Slide

6. The Beginning
   Medusa:
   Unmaintained and direct socket
   manipulation
   …
   

   View Slide

7. The Beginning
   …
   Twisted
   

   View Slide

8. Programming Models
   Single-threaded
   Multi-threaded
   Asynchronous
   

   View Slide

9. Single-threaded
   time
   

   View Slide

10. Single-threaded
    
    

    View Slide

11. Multi-threaded
    time
    

    View Slide

12. Multi-threaded
    
    

    View Slide

13. Event-driven
    time
    

    View Slide

14. Event-driven
    
    

    View Slide

15. The Reactor
    Waits on and handles events
    abstracts away platform-
    specific behavior
    

    View Slide

16. Event-loop
    while True:
    timeout = time_until_next_timed_event()
    events = wait_for_events(timeout)
    events += timed_events_until(now())
    for event in events:
    event.process()
    

    View Slide

17. “Twisted softens your
    brains and makes you feel
    like your head is actually a
    blender optimized for gray
    gloop.”
    

    View Slide

18. “It was created by a couple of
    dudes who dropped out of
    school, and a 16-year-old.
    HOW HARD COULD IT BE?”
    

    View Slide

19. The Box Metaphor
    

    View Slide

20. “How do I even get this
    thing to do anything?”
    

    View Slide

21. When you look for it, there is nothing to see.
    When you listen for it, there is nothing to
    hear.
    When you use it, it is inexhaustible.
    

    View Slide

22. from twisted.internet import reactor
    reactor.run()
    The World’s Largest NOP
    

    View Slide

23. “The Master does his job and then stops.
    He understands that the universe is
    forever out of control.”
    

    View Slide

24. It’s humongous!
    

    View Slide

25. “Core can fit into a floppy
    disk.”
    

    View Slide

26. It’s just code.
    

    View Slide

27. Know what you're
    doing.
    

    View Slide

28. View Slide

29. 
    

    View Slide