An introduction to Node.js application development

Introduction to Node.js application development Dr. Jayaraj Poroor Founder & CEO, Shelloid http://shelloid.com http://shelloid.org GTech TFG, Jan 21 2015

About Shelloid Open Source Technology (http://shelloid.org) Operational Log Intelligence (http://shelloid.com)

Server-side technology requirements ● Performance o Need optimized execution ● Concurrency o Need to support many concurrent client requests ● Library support o e.g., database interfacing. ● Framework support o For rapid application development.

Node.JS ● Performance o Google’s V8 VM with native JIT compilation ● Concurrency o Asynchronous I/O (libuv) + clustering ● Library support o 39K projects in Github ● Framework support o e.g., Express.JS

Synchronous vs Asynchronous I/O ● Synchronous I/O o Thread blocks till I/O request is complete. o e.g., $result = mysql_query(“....”); //PHP ● Asynchronous I/O o Thread does not block o Uses callback mechanism to notify completion o e.g., conn.query(“...”, function(err, rows) { } );

Node.JS Threading model 1. Single computational thread o Non-blocking, interleaved request processing o Background worker threads for I/O processing 2. Clustering to utilize multi-core machines 3. No shared memory between cluster processes.

Node.JS : When to use ● Great for o I/O-centric applications  e.g., DB queries, File I/O , network I/O, invocation of other web services. o Real-time communication  WebSockets, HTTP long polling ● Not so great for o Compute-centric applications  e.g., High-end machine learning backend

Event Loop Illustrated http://www.geekgirl.io/understanding-the-event-loop-in-nodejs/

Anatomy of a “hello world” Node.js var http = require('http'); var server = http.createServer(function (req, res) { res.writeHead(200, {'Content-Type': 'text/html'}); res.end('<h1>Hello World</h1>'); }); server.listen(3000); No separate HTTP engine like Apache required. Command: node app.js

Serving a file Code source: https://github.com/substack/stream-handbook Buffers the entire file in memory. ● Inefficient for large files. ● Client needs to wait till entire file is read.

Node.js Streams ● Data served in chunks. ● Data event fires whenever a new chunk is ready. Code source: Node.js in Action

Streams can be piped! File stream (input) is piped to the response stream (output). The response will employ chunked Transfer-Encoding. Code source: https://github.com/substack/stream-handbook

Package management ● npm (Node Package Manager) o Provides simple & powerful package management. o Reads module dependencies from package.json o Typical usage: npm install or npm update. o Can store all dependent modules locally or globally

A sample package.json { "name": "SomeApp", "description": "SomeApp Web Application", "version": "0.0.1", "private": true, "dependencies": { "express": "3.6.0", "connect": "2.15.0", "mysql": "*", } }

Secure HTTP with Node.js Code source: Node.js in Action Key and certificate files provided. Use gpg, openssl etc. to generate key and CSR.

Connect framework: Modular web apps Install: npm install connect

Connect: usage Create a Connect ‘app’. ● Will store all middleware. ● Itself just a function. Create a middleware ‘stack’. Requests will execute middleware functions till ‘next()’ is not called or end of stack is reached. Code source: https://www.npmjs.org/package/connect

Connect: usage (2) ● Middleware can be mounted on specific URL endpoints. ● Does basic routing. ● Error handler middleware. Create Connect-enabled server. Code source: https://www.npmjs.org/package/connect OR

Serving static files Static middleware configured with the folder from which files are served.

Express: Lightweight web framework Code Source: https://www.npmjs.org/package/express Routing

Bootstrapping Express application express -e output

Rendering views with Express Express configured with the views folder. View engine set as ejs. Looks up index.ejs in the views folder.

View lookup Source: Node.js in Action

Passing data to views Data passed to the view. photos is an array.

An example view photos array accessed here. title variable accessed.

Database connectivity npm install mysql var mysql = require('mysql'); var connection = mysql.createConnection({ host : 'localhost', user : 'me', password : 'secret' }); connection.connect(); connection.query('...', function(err, rows, fields) { if (err) throw err; connection.end(); }); https://github.com/felixge/node-mysql npms available for virtually any SQL/NoSQL database! Query completes only when the callback is invoked!

Authentication ● passport.js o Authentication middleware for node.js. o 140+ authentication strategies. o Supports OpenID and OAuth o http://passportjs.org o Session data can be serialized into a store like Redis. npm install passport

Read more ● Node.js in Action ● http://expressjs.com ● http://www.nodebeginner.org/

Using Shelloid npm install -g shelloid shelloid app-folder [env name] Learn more at http://shelloid.org Requires admin/super user privilege

Dr. Jayaraj Poroor Founder, Shelloid Systems Open source cloud-ready Node.js application server jayaraj@shelloid.com http://shelloid.com Thank You

An introduction to Node.js application development

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