Quick 30 minute intro to Node.js

A broad sweep of Node.js with keynote, presenter notes (this file) and demos.

Based heavily on Ryan Dahl's excellent presentations:

• http://www.youtube.com/watch?v=jo_B4LTHi3I
• http://www.youtube.com/watch?v=F6k8lTrAE2g

User Interaction

• Handle loads of concurrent connections (eg a map tile server)
• Need to do chat
• 'Realtime' interaction (or realtime enough)

How did HTTP deal with it?

• Apache: 1 thread per http request
• Nginx, lighttp: Event Loop

Need

High performance customisable server (not just HTTP)

Solution

multiplex IO into single thread

Goal

Write high performance servers easily (hard has already been done!)

In C, these servers look like

• use events
• have non-blocking IO
• no shared memory
• If need to handle more traffic, open more event loop processes
• Can handle 20-30k TCP connections per thread. Quite scalable.

In other languages, Ruby, Erlang, Python

* Have abstractions
* 'Green threads' Actually running ontop of a single OS thread and an event loop.
* 'Erlang processes' 'green processes/threads' running in a separate address space + scheduler - multicore happy and allows you to kill an individual process. Still green threads though. Still running on an EL.
* Event loops (eventmachine (Ruby), twisted(Python)). 

Abstractions are still EL and non-blocking IO.

Problems with writing EL+nonblocking I/O in C et al.

• If C, have to write in C
• Everything has to be non-blocking.
• All or nothing. Can't mix libraries (eg. MySQL doesn't have a non-blocking client)

Javascript

• Performance arms race (Google Apple, Moz, Opera, MS...)
• No preconceived ideas about I/O
• Browsers are single threaded, and non-blocking.
• People already get it (mouseover).

V8 performance

• Fastest scripting language now
• V8 is an optimising compiler to machine code
• graphs

Node is

• Set of bindings on top of V8 for non-browser work: sockets, files
• purely non-blocking interfaces, so beginners can achieve decent concurrency
• Only 1 thread, only 1 stack
• lots of low-level features
• Emphasis on networking
• Excellent socket/http support

Questions

• Single threaded
• No automatic scaling
• What about multicore?
  • Open new processes.
  • communicate over sendmessage, or IPC webworkers.
  • Node: low level. You have to make your own.

Install

look up on github: https://github.com/joyent/node/wiki/Installation

Quick 1 min

• REPL
• process object == windows object
• tab completion
• .exit

Demo

Work through demo folder

Packages

• npm
• http servers
• database drivers etc

Any major pain points?

• Exceptions - backtraces is only made of the current callback scope

Resources

• http://nodejs.org/
• http://www.youtube.com/watch?v=jo_B4LTHi3I
• http://www.youtube.com/watch?v=F6k8lTrAE2g
• http://developer.yahoo.com/yui/theater/ (JS vids)
• https://github.com/tokumine/Node.js-Introduction