1. Asynchronous I/O in NodeJS - Standard and challenge of web programming? Pham Cong Dinh @ SkunkWorks @pcdinh BarCamp Saigon 2011 Follow us on Twitter: @teamskunkworks

3. Things can be changed

4. No standard at the moment

5. Unix only

7. JVM

9. Events / Non-blocking I/O From http://bethesignal.org/

11. Threads: A process contains multiple threads. A single thread is assigned to handle an incoming request. Thread-per-request model

12. Events: A process consists of the processing of a series of events. At any instant in time, a single event/request is being processed. The process is not blocked on I/O request.

13. Request handling: Process / Threads / Events Threads shares ● D efault share memor y ● F ile descriptors ● Filesystem context ● Signals and S ignal handling

14. Request handling: Process / Threads / Events Thread creation is expensive - From iobound.com

15. Request handling: Process / Threads / Events Context switching is expensive

16. Request handling: Process / Threads / Events Blocking model: Process and Threads

17. Request handling: Process / Threads / Events Non-blocking model: Events

18. Request handling: Event-driven IO loop issue poll vs. epoll epoll: O(1) or O(n=active)

19. Request handling: Event-driven callback issues Non-blocking IO Loop vs. Blocking callback Event dispatching is not blocked Callback can be blocked Mixing asynchronous code and synchronous code can be bad

21. libeio for asynchonous file I/O

22. c-ares for asynchronous DNS requests and name resolution.

23. evcom (by Ryan Dahl) is a stream socket library on top of libev.

25. Most “objects” in NodeJS are Event Emitters (http server/client, etc.)

26. Most low level “functions” take callbacks. (posix API, DNS lookups, etc.) Blocking code var a = db.query('SELECT A'); console.log('result a:', a); Non-blocking code using callback db.query('SELECT A', function(result) { console.log('result a:', result); });

28. Do things in a specific order.

29. You must keep track of what is done at a point of time

30. Hard to handle failures

31. Nested callbacks can be hard to read

35. Flow-JS https://github.com/willconant/flow-js

36. Node-Promise https://github.com/kriszyp/node-promise

40. http://tamejs.org/