Playing With Fire - An Introduction to Node.js

PLAYING WITH FIRE
(ROCKET FUEL ACTUALLY)
An introduction to node.js

Mike Hagedorn Anthony Broussard
@mwhagedorn @quantumpotato
codemav.com/mwhagedorn codemav.com/quantumpotato
mike@silverchairsolutions.com anthony@chaione.com

IN THE BEGINNING...

Server-side Javascript

IN THE BEGINNING...

Server-side Javascript
(it sucked)

SERVER-SIDE JAVASCRIPT

•Netscape Livewire(1996)
•Rhino(1997)
•Several others since(like 50)

Y SO BAD?

•Slow Engines
•Javascript’s Perception (until recently)
•Much better alternatives

Y IZ BETTR NAO?

Lots of Competition
•SpiderMonkey
•JavascriptCore
•Chakra
Javascript is cool now!

WHAT IS NODE.JS?

•Created By Ryan Dahl
•Google’s V8 Engine (No DOM)
•Uses Nonblocking I/O
•Single Threaded
•A New Way To Build Scalable Network Platforms

WHY SHOULD YOU CARE?
•Its Fast
> summary(node1$ttime)
Min. 1st Qu. Median Mean 3rd Qu. Max.
0.0000 0.0000 1.0000 0.7437 1.0000 106.0000

> summary(thin1$ttime)
0.000 1.000 1.000 1.122 1.000 74.000

> summary(narwhal1$ttime)
15.00 22.00 23.00 23.74 24.00 88.00

> summary(v8cgi1$ttime)
12.00 13.00 13.00 14.49 18.00 39.00

•It can handle LOTS of concurrent transactions


• Makes near real time things easy
• Its small
• Its Javascript
•(Second most used language on Github)

WHO’S USING IT

Others: http://doiop.com/rocket-node

HELLO WORLD
server.js

setTimeout(function(){
console.log(“world”)
},2000);
console.log(“hello”);

HELLO WORLD
server.js

},2000);

$ node server.js
hello
world

HELLO WORLD
server.js

},2000);
print(“hello”);
sleep(2000);
print(“world”);

$ node server.js
hello
world

NON-BLOCKING I/O
(asynchronous is the new black)

BLOCKING I/O

var a = db.query('SELECT A');
console.log('result a:', a);

var b = db.query('SELECT B');
console.log('result b:', b);

Time = SUM(A, B)

NON-BLOCKING I/O

db.query('SELECT A', function(result) {
console.log('result a:', result);
});

db.query('SELECT B', function(result) {
console.log('result b:', result);
});

Time = MAX(A, B)

SINGLE THREADED!
You have to use callbacks!

db.query('SELECT A', function(result) {
object.mySlowCall(result, function(){
console.log(“my result”);
})
});

WHY ISN’T EVERYONE USING
NON-BLOCKING I/O?
There are cultural and infrastructural
reasons

CULTURAL BIAS

We’re taught I/O with this:

puts(“Enter your name:”)
var name = gets()

We’re taught to demand input and do
nothing until we have it.

CULTURAL BIAS

This code:
puts(“Enter your name:”)
var name = gets(function(name){
puts(“Name: “)+name);
})

is rejected as TOO COMPLICATED

MISSING INFRASTRUCTURE
So why isn’t everyone using event loops?

Single threaded event loops require I/O to be non blocking

Most libraries are not.

OTHER APPROACHES?
•Twisted
•EventMachine
•Others
•Have lots of blocking libs to contend with
•From the start Node has never provided a blocking API
•Its a clean slate
•These approaches can be hard to use

JAVASCRIPT...

•Has had event loops from the beginning
•Anonymous functions, closures
•Single threaded
•The culture of Javascript embraces evented
programming

GREAT FOR

•Single Page Apps
•Realtime updates
•Processors/Crawlers
•Process Monitoring
•File Uploading

INSTALLING
OSX
$ brew install node

Linux
$ git clone ....
$ configure
$ make

Windows
Not Yet (version 0.6)

INSTALLING NPM

•Node Package Manager
•Similar to RubyGems, Python easy_install

$ curl http://npmjs.org/install.sh | sh

COMMON JS MODULES
hello.js

exports.world = function(){
return “Hello World”;
}
main.js
var hello = require(‘./hello’);
var sys = require(‘sys’);
sys.puts(hello.world());

$ node main.js #Hello World

EVENTS
{EventEmitter} = require ‘events’
emitter = new EventEmitter
emitter.on ‘foo’, -> console.log ‘bar’
emitter.emitusual new_monster event. And check out how much nicer our
emitting the ‘foo’
dependency graph has become!

http://pragprog.com/magazines/2011-08/content
Imagine No Dependencies
A lot of Node developers will tell you that attaching things to global rather
than exports is a no-no. And if you’re packaging your code as a library, or trying
to make your code reusable, then they’re right. But if you’re developing a
standalone application, then go ahead and let yourself declare a few globals.

QUEUEING AN EVENT

function longFunction(){};
process.nextTick(longFunction);

Call longfunction on next time through event loop

EMITTING AN EVENT
var events = require('events');

var eventEmitter = new events.EventEmitter();

eventEmitter.on('someOccurence', function(message){
console.log(message);
});

eventEmitter.emit('someOccurence', 'Something happened!');

MANAGING ASYNCHRONCITY
A B C

use async!

A B C

var operation = function(a_data, b_data, callback){
async.series([
function(as_callback),
function(err,results){ //[resulta, resultb] }
]);
}

A
C

B

var operation = function(a_data, b_data, callback){
async.parallel([
function(err,results){ //[resulta, resultb] }
]);
}

EXPRESS WEB FRAMEWORK

var app = express.createServer();

app.get('/', function(req, res){
res.send('Hello World');
});

app.listen(3000);

COFFEESCRIPT
•“Little language that compiles to javascript”
•“It’s just javascript”
• More ruby-like

COFFEESCRIPT
• More ruby-like
square = (x) -> x * x

COFFEESCRIPT
• More ruby-like
square = (x) -> x * x

square = function(x){
return x * x;
}

QUESTIONS?
http://spkr8.com/t/8178

Mike Hagedorn Anthony Broussard
@mwhagedorn @quantumpotato
mike@silverchairsolutions.com anthony@chaione.com

Playing With Fire - An Introduction to Node.js

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