Introduction to Node.js: perspectives from a Drupal dev

Introduction to Node.js
Perspectives from a Drupal dev
Mike Cantelon, Vancouver Drupal Users Group, Nov. 25, 2010
Thursday, November 25, 2010

I am:
A longtime PHP dev
Devop for The Georgia Straight
Experimenting with JS/SSJS and HTML5
http://mikecantelon.com
http://github.com/mcantelon

WHY NODE.JS?

wordsquared.com: Real-time
HTML/JS Scrabble MMO

The real-time web
Real-time applications are an interesting web subset
Examples: Twitter, Etherpad, games, monitoring
Real-time paradigm will spawn new types of apps

Three barriers to real-time
Conventional languages can be slow
Conventional web servers can be slow
Conventional databases are slow

Node.js eliminates two
Conventional languages can be slow
Conventional web servers can be slow

http://www.slideshare.net/Vodafonedeveloper/nodejs-vs-phpapache
Node.js vs PHP/Apache

So what exactly is Node.js?
Server-side Javascript (SSJS) implementation
“Asynchronous” (more on that later)
Built using V8 (JS engine used in Chrome Browser)

Advantages over PHP
Javascript is a cleaner language
Asynchronous execution increases performance
Node.js is suitable for writing TCP/IP apps

“Asynchronous”?
Also known as “event-based”
Think of it as deﬁning actions triggered by events
CPU spends less time waiting around

More beneﬁts of SSJS
Requires less mental context switching for devs
Allows sharing of logic between client and server side
Server-side JQuery for screen scraping? Yes!

What about that last barrier?
Conventional languages are slow
Conventional servers are slow

MongoDB is one solution
MongoDB is generally faster than SQL databases
MongoDB queries are written in Javascript, not SQL
MongoDB works well with node.js

And Drupal?
Drupal is great for managing content
Node.js has no killer CMS
Node.js can pull data from Drupal (details later)

This looks conceptually like...

SSJS HELLO WORLD

Node.js isn’t hard to learn
Knowing Javascript is the hard part
Node.js is accessible
Express is a framework that makes Node.js easier

Hello World in Node.js shell
var sys = require('sys');
sys.puts('Hello world');

Node.js server Hello World
var http = require('http');
http.createServer(function (req, res) {
res.writeHead(200, {'Content-Type': 'text/plain'});
res.end('Hello Worldn');
}).listen(8124, "127.0.0.1");

Hello World in Express
var express = require('express');
var app = express.createServer();
app.get('/', function(req, res){
res.send('Hello World');
});
app.listen(8124);

Why use Express?
Handles routing and redirection
Nice templating support
Provides sessions

Express Templating Support
Supports EJS, HAML, SASS, Jade (HAML variant)
Extend with app-speciﬁc helper functions
Provides “partials” (subtemplates)

app.get('/', function(req, res){
res.render('index.haml', {
locals: { title: 'My Site' }
});
});
Templating Example

SETTING UP NODE.JS

Installing Node.js
OS X: build from source or brew install node
Linux: build from source
Build instructions at http://nodejs.org/#download

Installing NPM
NPM lets you easily install node.js modules
OS X: brew install npm
Instructions for manual install:
http://mikecantelon.com/npm

Installing Express
npm install express
Now the command express will set up an example
Express app for you

Installing MongoDB
OS X: build from source or brew install mongodb
Linux: http://www.mongodb.org/display/DOCS/
Quickstart+Unix
npm install mongodb

DRUPAL -> NODE.JS

Drupal as a datastore
One way Node.js and Drupal can work together is
having Drupal be the storehouse for important content
requiring long-term management

Something like...

Serve data, not just pages
For realtime apps you’re going to want to serve chunks
of data to the browser rather than whole pages
Whole pages take longer to render and use more
bandwidth to transmit
Leverage the browser as much as possible

Serving a page...
1. Browser requests a URL
2. Server grabs some data from a database and
dresses it up as a page using a template.
3. Whole page gets sent back to browser

...vs Serving Data
1. Browser requests some data
2. Server sends back data
3. Browser templates data and outputs HTML
into the existing page

Where to serve data from
Pulling Drupal data directly to the browser is quick to
implement, but puts more stress on your Drupal stack
The alternative is to pull Drupal data to node.js and
cache using a datastore like MongoDB
Data can then be relayed via AJAX or Socket.io

DRUPAL DATA SHARING

Javascript For Data Sharing
JSON is the duct tape of the web
drupal_to_js turns any chunk of data into JSON
Drupal Views can output JSON via Views Datasource

What JSON looks like
{
'drupal': {
'language': 'PHP',
'license': 'GPL',
'developed_by': {
'individuals',
'organizations',
'companies'
}
}
}

Drupal pumping out JSON

Example: RSS to JSON via Views

What our example will do
Use the Aggregator module to pull data from an RSS
feed (speciﬁcally “Drupal Planet”)
Use Views, via the Views JSON module, to publish the
aggregator items as JSON data

Install Views Datasource

Add View

Add Page Display and Path

Add Paging

Add Fields

Set Style to JSON

Set Feed/Category ID

Save View and Check Path

Demo use of Drupal/JSON...
[demo]
http://github.com/mcantelon/Drupalurk

Hack for Paging (v6 beta2)
function mytheme_preprocess_views_views_json_style_simple(&$vars) {
global $pager_total, $pager_page_array;
$element = $vars['view']->pager['element'];
$vars['rows']['pager'] = array(
'total' => $pager_total[$element],
'current' => $pager_page_array[$element]
);
}
http://gist.github.com/581974
Views Datasource needs theme tweak to make paging work
Stick the snippet below into your theme’s template.php

Hack for Paging (v6 beta2)
This enables you to add &page=<page number
starting at 0> to JSON calls
You can then implement your own JS paging

Possible JSON View Uses
Pull front-page content
Pull content by taxonomy
Pull recent comments
Whatever else you can do with a view

Pulling JSON into Node.js
var sys = require('sys'),
rest = require('restler-aaronblohowiak'),
item,
node
rest.get('http://mikecantelon.com/jsontest/News')
.addListener('complete', function(data) {
for(item in data.nodes) {
node = data.nodes[item].node
sys.puts(node.Title)
sys.puts(node.Body)
}
})
http://gist.github.com/608741
restler module allows easy HTTP JSON requests

TALKING TO MONGODB

Things to remember
Can create databases and schema on-the-ﬂy
Queries are Javascript
A “collection” is similar to an SQL DB’s “table”
MongoDB has a shell so easy to experiment

Doing something to data
1. Open server DB connection
2. Open database
3. Open collection
4. Do something to the collection

Opening server DB connection
var mongo = require('mongodb');
var port = mongo.Connection.DEFAULT_PORT;
var db = new mongo.Db(
'classroom',
new mongo.Server('localhost', port, {}),
{}
);

Opening database
db.open(function(err, db) {
// stuff gets done in here
});

Opening a collection
db.collection(
'students',
function(err, collection) {
// collection operations here
}
);

Removing from a collection
collection.remove(
function(err, collection) {
// records are now gone!
}
);

Adding some records
// make four students with random ages
var names
= ['Rick', 'Jane', 'Bob', 'Lisa'];
var index;
for (index in names) {
collection.insert({
'name': (names[index]),
'age':
Math.round(Math.random(4)*10)+18
});
}

Displaying data from records
// display names
collection.find({}, {},
function(err, cursor) {
cursor.toArray(
function(err, students) {
var index;
for(index in students) {
sys.puts(students[index].name);
};
}
);
}
);

DEPLOYING NODE.JS

Node.js isn’t a daemon
Like PHP, node.js doesn’t run as a daemon
This means that naive deployment would require
keeping a terminal open
There are a number of ways to deal with this...

Upstart (Ubuntu/some other distros)
Make a config file for each app in /etc/init
Name config file my_app.conf and set as executable
Start app using: sudo start my_app

Installing Upstart
Ubuntu: apt-get install upstart
Linux: http://upstart.ubuntu.com/download.html

System V init script (the right way)
rc.local/custom script (quick and dirty)
Gnu screen (for temporary deployment)
No Upstart? (Centos/some other distros)

Requires adding a line to /etc/rc.local and a script
Example line in rc.local triggers script at startup:
su - mike -c "/home/mike/drupalchat/RUN.sh" &
Script should set NODE_PATH if you’re using npm
rc.local/custom script

Example script
#!/bin/bash
cd /home/mike/drupalchat
export NODE_PATH=/home/mike/root
/usr/local/bin/node server.js

Hotnode will restart node.js when you change a ﬁle
Start app with hotloading: hotnode my_app.js
Installation: npm install hotnode
Hotnode

BONUS! WEBSOCKETS

What are WebSockets?
WebSockets are an “HTML5” technology for two-way
TCP/IP textual communication
Modern browsers, like Chrome and Firefox 4, offer a
Javascript WebSockets interface

Why not just use AJAX?
AJAX is a hack that uses HTTP for communication
HTTP request/response cycle has a lot of overhead
WebSockets increase speed, lessen bandwidth use

Implementing with Socket.io
Socket.io is a client/server websocket solution, using
Node.js for the server side
The client library tries WebSockets, but falls back to
other mechanisms when talking to old browsers

Questions? Ideas?

Flickr Credits
http://www.flickr.com/photos/sidehike/459483568/
http://www.flickr.com/photos/wysz/86758900/
http://www.flickr.com/photos/generated/291537716/
http://www.flickr.com/photos/gsfc/3720663082/
http://www.flickr.com/photos/skreuzer/354316778/
http://www.flickr.com/photos/ubookworm/455760111/
http://www.flickr.com/photos/batega/1596898776/
http://www.flickr.com/photos/batigolix/3778363253/
http://www.flickr.com/photos/wwworks/4472384764/
http://www.flickr.com/photos/19779889@N00/4398186065/
http://www.flickr.com/photos/theplanetdotcom/4878809615/
http://www.flickr.com/photos/estherase/177188677/

Resources
Node.js, Express.js and MongoDB
http://nodejs.org/
http://expressjs.com/
http://www.mongodb.org/
Socket.io
http://socket.io/
This presentation
http://mikecantelon.com/drupal-nodejs

Introduction to Node.js: perspectives from a Drupal dev

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