Introduction to

M. Khurrum QureshiSr. Software Engineer

Node’s Goal is to provide an easy way to build scalable

network programs.

Node.js is NOT anotherweb framework!

But you can create a web framework using NPM modules.

Node.js is…Web ServerTCP Server

Awesome Robot ControllerCommand Line Application

Proxy ServerStreaming ServerVoiceMail ServerMusic Machine

Anything that has to deal with high I/O

Node.js isServer Side JavaScript!

Node.js is

FUN!

Why Node.js?• Non Blocking I/O• Based on Chrome’s V8 Engines (FAST!)• 15,000+ Modules • Active Community (IRC, Mailing Lists, Twitter,

Github)• Mac, Linux and Windows (all first class citizens)• One Language for Frontend and Backend• JavaScript is the Language of the Web

Node.js Good Use Cases• JSON APIsBuilding light-weight REST / JSON api's is something where node.js really shines. Its non-blocking I/O model combined with JavaScript make it a great choice for wrapping other data sources such as databases or web services and exposing them via a JSON interface.

• Single Page AppsIf you are planning to write an AJAX heavy single page app (think gmail), node.js is a great fit as well. The ability to process many requests / seconds with low response times, as well as sharing things like validation code between the client and server make it a great choice for modern web applications that do lots of processing on the client.

Node.js Good Use Cases• Shelling out to Unix ToolsWith node.js still being young, it's tempting to re-invent all kinds of software for it. However, an even better approach is tapping into the vast universe of existing command line tools. Node's ability to spawn thousands of child processes and treating their outputs as a stream makes it an ideal choice for those seeking to leverage existing software.

• Streaming DataTraditional web stacks often treat http requests and responses as atomic events. However, the truth is that they are streams, and many cool node.js applications can be built to take advantage of this fact. One great example is parsing file uploads in real time, as well as building proxies between different data layers.

Node.js Good Use Cases• Soft Real Time ApplicationsAnother great aspect of node.js is the ease at which you can develop soft real time systems. By that I mean stuff like twitter, chat software, sport bets or interfaces to instant messaging networks.

Basic HTTP Servervar http = require('http'); var server = http.createServer(function (req, res) {  res.writeHead(200);  res.end('Hello World');}); server.listen(4000);

Some people use the core http module to

build their web apps, most use a framework

like Expressor Connect or Flatiron or Tako or Derby or Geddy or Mojito or …

Visithttp://expressjs.com/guide.html

for a detailed guide on using Express

What is Non-Blocking I/O?And why should I care?

Blocking I/

270ms = SUM(user, activities, leaderboard)

// Get User – 20ms$query = 'SELECT * FROM users WHERE id = ?';$users = query($query, array($id));print_r($users); // Get Activities – 100ms$query = 'SELECT * FROM activities ORDER BY timestamp LIMIT 50';$activities = query($query);print_r($activities); // Get Leader Board – 150ms$query = 'SELECT count(points) as total, user_id FROM activities LIMIT 50';$leader_board = query($query);

Non-Blocking I/

150ms = MAX(user, activities, leaderboard)

// Get User – 20msvar query = 'SELECT * FROM users WHERE id = ?';db.query(query, [userId], function (err, results) {  console.log(results);}); // Get Activities – 100msvar query = 'SELECT * FROM activities ORDER BY timestamp LIMIT 50';db.query(query, function (err, results) {  console.log(results);}); // Get Leader Board – 150msvar query = 'SELECT count(points) as total, user_id FROM activities LIMIT 50';db.query(query, function (err, results) {  console.log(results);});

The most jarring thing about Server Side JavaScript

is thinking in callbacks

The Node Callback PatternawesomeFunction(arg, function (err, data) {   if (err) {      // Handle Error   }      // Do something awesome with results.});

• Error first then success… ALWAYS!• Because this is the de-facto standard 99.99999% of the time

you will be able to guess how a Node library will work.

Callbacks are the Devil’s Work!Don’t go down this rabbit hole…

One of the biggest mistakes is to get yourself in to callback hell by nesting callbacks inside of

callbacks inside of more callbacks.

var userQuery = 'SELECT * FROM users WHERE id = ?';var activityQuery = 'SELECT * FROM activities ORDER BY timestamp LIMIT 50';var leaderBoardQuery = 'SELECT count(points) as total, user_id FROM activities LIMIT 50'; db.query(userQuery, [id], function (userErr, userResults) {   db.query(activityQuery, function (activityErr, activityResults) {      db.query(leaderBoardQuery, function (leaderBoardErr, leaderBoardResults) {          // Do something here       });   });});

Avoiding Callback Hell• Keep your code shallow• Break up your code into small chunks• Use a sequential library like async• Visit http://callbackhell.com

Async to the rescue!var async = require('async');var db = require(’db'); function getUser (callback) {  var query = 'SELECT * FROM users WHERE id = ?';  db.query(query, [userId], callback);} function getActivities (callback) {  var query = 'SELECT * FROM activities ORDER BY timestamp LIMIT 50';  db.query(query, callback);} function getLeaderBoard (callback) {  var query = 'SELECT count(points) as total, user_id FROM activities LIMIT 50';  db.query(query, callback);} var tasks = [getUser, getActivities, getLeaderBoard];async.parallel(tasks, function (err, results) {  var user = results[0];  var activities = results[1];  var leaderBoard = results[2];});

Visithttps://github.com/caolan/async

for a detailed guide on using the async module.

Async provides several useful patterns for asynchronous control flow

including: parallel, series, waterfall, auto and queue.

The Node Package Managerotherwise know as… NPM

It’s how you harness the awesomeness of the Node.js community!

Using NPMIt’s standard practice to install modules locally for your current project. Modules are installed in the ./node_modules in the current directory.

To Install a new module

npm install <module>

To find a module in the NPM repository

npm search <search string>

To list the modules (and their dependencies) in the current project

npm list

To see module details

npm info <module>

DON’T INSTALL MODULES GLOBALLY!

Unless they are tools like node-dev, jake, express, minify-js OR linked development modules but more on that later.

NPM is awesome sauce!

Visithttps://npmjs.org

for more details about NPM and to browse the current NPM Repository

Node.js Modules• async • connect • express • mongodb-

native-driver• request

• apn • ql.io-engine • pem • winston • winston-

mongodb

Node.js Modules• node-sql • nodemailer • connect-http-

signature• http-signature• underscore

• file-utils • validator • mongoskin • passport.Js • yql

Node.js Modules• node-gcm • forever • mongodb_s3_b

ackup• nconf

• node-sqlserver• Socket-io• generic-pool• And many

others

Deployment Platforms• Amazon EC2 • Windows Azure• Heroku• Joynet• Nodejistu

Questions?

Introduction to

NoSql• Non-Relational• Horizontally Scalable• Distributed• Schema-Free• Open-Source• Replication Support • Simple API

NoSql Flavours• Key-value Store.• Graph• Big Table• Document Store

mongoDB Overview• Document Database

– Documents (objects) map nicely to programming language data types. – Embedded documents and arrays reduce need for joins. – Dynamic schema

• High Performance– Embedding makes reads and writes fast.– Indexes can include keys from embedded documents and arrays.– Optional streaming writes (no acknowledgments).

• High Availability– Replicated servers with automatic master failover.

mongoDB Overview• Easy Scalability

– Automatic sharding distributes collection data across machines.

mongoDB Data Model• MongoDB instance hosts a number of databases.• A database holds a set of collections.• A collection holds a set of documents.• A document is a set of key-value pairs. • Documents have dynamic schema.

Document Structure• Data is stored in the form of JSON data.(Which

internally stored as BSON){ "_id" : ObjectId("4ccbfc75bd163019417c27f8"), "title": “Hello World! ", "author": { "firstname": "Joe", "lastname": "Bloggs" }, "tags": ["test", "foo", "bar"] }

Key mongoDB Features• Flexibility• Power• Speed/Scaling• Ease of use

Questions?