Becoming a Node.js Ninja on Cloud Foundry - Open Tour London
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Becoming a Node.js Ninja on Cloud Foundry - Open Tour London

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Presentation from the Cloud Foundry Open Tour, London, May 1 2012 - the concepts behind node.js, some code examples, and some sample applications which run on Cloud Foundry. Code samples at ...

Presentation from the Cloud Foundry Open Tour, London, May 1 2012 - the concepts behind node.js, some code examples, and some sample applications which run on Cloud Foundry. Code samples at http://github.com/rajaraodv

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    Becoming a Node.js Ninja on Cloud Foundry - Open Tour London Becoming a Node.js Ninja on Cloud Foundry - Open Tour London Presentation Transcript

    • Becoming a Node.js ninja onCloud Foundry Raja Rao DV (@rajaraodv) Andy Piper (@andypiper) Cloud Foundry Developer AdvocatesMay 2012 www.cloudfoundry.com © 2009 VMware Inc. All rights reserved
    • Agenda1. About Node.js • Internal working of Node.js • Buzz around Node.js • Who is using it • What kind of apps are being built2. Coding in Node.js • Sync v/s Async coding (Callbacks) • Classes & Modules (CommonJS) • npm & package.json • Node.js EventEmitters3. Node.js & Cloud Foundry (w/ demo) • Hello World app in Cloud Foundry • Using Sticky Sessions • CloudFoundry Module & connecting to Redis, MongoDB etc. • Express.js (RESTful) app • Socket.io + Express.js (Real-time) app2
    • About Node.jsNode.js is a platform to build fast and scalable network applications. It isbuilt on Google Chrome’s v8 engine & implements event-driven, non-blocking I/O model.- It is ~80% C/C++ & ~20% JS (APIs)- Uses CommonJS module system.- Executes JavaScript on the server- Built by Ryan Dahl & sponsored by Joyent Ryan Dahl (Node.js creator) 3
    • What is the biggest advantage of Node.js? Biggest thing Node.js brings to the table (other than JS) is savings in I/O cost4
    • The cost of I/O http://blog.mixu.net/2011/02/01/understanding-the-node-js-event-loop/5
    • So how does Node.js save I/O cost? Node.js saves I/O cost by implementing event driven, non-blocking I/O model6
    • Event-driven, non-blocking I/O platform/serverWhat exactly is a event-driven, non-blocking platform/server?How is it different from a multi-threaded platform/server? Multi-threaded blocking server v/s Event-driven, non-blocking server 7
    • Multi-threaded server - Threads are spawned for every connection User1 I/O request T1 DB Blocking FS Multi threaded server T Thread8
    • Multi-threaded server - Threads are spawned for every connection User1 I/O request T1 DB User2 I/O request T2 Blocking FS Multi threaded server T Thread8
    • Multi-threaded server - Threads are spawned for every connection User1 I/O request T1 DB User2 I/O request T2 Blocking User3refreshes 2 times T3 T4 T5 FS Multi threaded server T Thread 8
    • Multi-threaded server - Threads are spawned for every connection User1 I/O request T1 DB User2 I/O request T2 Blocking I/O User3refreshes 2 times T3 T4 T5 T7 FS User4 T6 T8 T9refreshes 3 times Multi threaded server T Thread Because every I/O request is blocking, server spawns a thread per connection to support multiple requests 8
    • Non-blocking & Evented I/O (Node.js server) JS C/C++ Libio POSIX Async DB T1 V8 Threads Event loop (Libev) t2 t1 Single thread t4 serves t3 all users t6 t5 t7 FST1 JS Thread runningV8 your code (Single threaded) Node.jst1 POSIX threads doing t2 async I/O (multi-threaded)t3 9
    • Non-blocking & Evented I/O (Node.js server) JS C/C++ T1 Libio User1 I/O request V8 POSIX Async DB Threads Event loop (Libev) t2 t1 Single thread t4 serves t3 all users t6 t5 t7 FST1 JS Thread runningV8 your code (Single threaded) Node.jst1 POSIX threads doing t2 async I/O (multi-threaded)t3 9
    • Non-blocking & Evented I/O (Node.js server) JS C/C++ T1 Libio User1 I/O request V8 POSIX Async DB Threads Event loop (Libev) delegate I/O to Non-blocking t2 I/O libeio t1 Single thread t4 serves t3 all users t6 t5 t7 FST1 JS Thread runningV8 your code (Single threaded) Node.jst1 POSIX threads doing t2 async I/O (multi-threaded)t3 9
    • Non-blocking & Evented I/O (Node.js server) JS C/C++ T1 Libio User1 I/O request V8 POSIX Async DB Threads Event loop User2 I/O request (Libev) delegate I/O to Non-blocking t2 I/O libeio t1 Single thread t4 serves t3 all users t6 t5 t7 FST1 JS Thread runningV8 your code (Single threaded) Node.jst1 POSIX threads doing t2 async I/O (multi-threaded)t3 9
    • Non-blocking & Evented I/O (Node.js server) JS C/C++ User1 I/O request Libio POSIX Async DB Threads Event loop User2 I/O request (Libev) T1 delegate I/O to Non-blocking t2 I/O V8 libeio t1 Single thread t4 serves t3 all users t6 t5 t7 FS I/O result returned 2 EL after x timeT1 JS Thread runningV8 your code (Single threaded) Node.jst1 POSIX threads doing t2 async I/O (multi-threaded)t3 9
    • Non-blocking & Evented I/O (Node.js server) JS C/C++ User1 I/O request Libio POSIX Async DB Threads Event loop User2 I/O request (Libev) T1 delegate I/O to Non-blocking t2 I/O V8 libeio User3 t1 Singlerefreshes 2 times thread t4 serves t3 all users t6 User4 t5refreshes 3 times t7 FS I/O result returned T1 2 EL after x time V8 T1 JS Thread running V8 your code (Single threaded) Node.js t1 POSIX threads doing t2 async I/O (multi-threaded) t3 Everything except your (JS) code is run in parallel (by libio) 9
    • Event-driven, non-blocking I/O serverReal-world example of the two models? Multi-threaded blocking server (Apache) v/s Event-driven, non-blocking server (Nginx) 10
    • Apache v/s Nginx: performance Reqs/sec v/s concurrent connections At ~4000 concurrent connections, - Nginx can serve ~9000 reqs/sec - Apache can serve ~3000 reqs/sec Ref: http://blog.webfaction.com/a-little-holiday-present11
    • Apache v/s Nginx: Memory usage Memory v/s concurrent connections At ~4000 concurrent connections, - Nginx uses 3MB memory - Apache uses 40MB memory Ref: http://blog.webfaction.com/a-little-holiday-present12
    • Saving I/O is great, what else is happening w/ Node.js? Let’s look at community, libraries, buzz around Node.js13
    • Other things going on for Node.js 2nd most popular watched on Github14
    • Other things going on for Node.js 9,000+ libraries/modules/servers High-level library categories Web frameworks Oracle Multiple protocols Command Line Option Parsers Routers NoSQL and Key/Value HTTP Parser Generators Static file servers Mongo FTP Other Parsers Hive E-mail Debugging / Console Utilities Microframeworks Redis XMPP Compression Frameworks CouchDB Other networking Graphics Middleware Other NoSQL implementations RPC Sound JSGI Miscellaneous and multiple DB Web Sockets & Ajax Payment Gateways Connect Templating Message Queues API clients Other middleware CSS Engines Class systems Control flow / Async goodies Other Content Management Systems Testing / Spec Frameworks I18n and L10n modules Database Build and Deployment Wrappers Boilerplates Package Management Systems Parsers Continuous Integration Tools MS SQL Server Module Loader JSON DDD, CQRS, EventSourcing PostgreSQL OpenSSL / Crypto / Hashing XML Desktop application related MySQL SMTP JavaScript threads SQLite TCP / IP Other https://github.com/joyent/node/wiki/modules15
    • Other things going on for Node.js Node in Production • LinkedIn, Yahoo!, Yammer, eBay, Twitter etc. • >1000 other companies/startups are using it in production All kinds of interesting apps: End-user apps: • Real-time apps • Mobile apps • CRMs, Web sites etc. etc. Platform apps (Servers / Services): • Node-http-proxy - Node.js implementation of reverse proxy like nginx • LdapJS.org - Node.js implementation of LDAP server itself • SMTP - Node.js implementation of SMTP server itself • XMPP, SSH, RPC, many more.16
    • Agenda – part 21. About Node.js • Internal working of Node.js • Buzz around Node.js • Who is using it • What kind of apps are being built2. Coding in Node.js • Sync v/s Async coding (Callbacks) • Classes & Modules (CommonJS) • npm & package.json • Node.js EventEmitters3. Node.js & Cloud Foundry (w/ demo) • Hello World app in Cloud Foundry • Using Sticky Sessions • CloudFoundry Module & connecting to Redis, MongoDB etc. • Express.js (RESTful) app • Socket.io + Express.js (Real-time) app17
    • Let’s look at the code...How does async code differ from sync (regular) code? Synchronous code v/s Asynchronous Code 18
    • Callbacks – Control flow Use case: Let’s say we have an item’s id and want to get its name from DB and print it//Synchronous & blocking code //Async & non-blocking codefunction getItemNameById(id) { function getItemNameById(id, callback) { //blocks or waits for DB db.get(id, callback); //step 2 return db.get(id); //step 2 //nothing is returned here} }var name = getItemNameById(100); //step 1 //step 3 Some internal function calls the callback w/ result//print name in step 3console.log(name); //step 3 //You create a callback helper function function displayHelperCallback(name) { console.log(name); //step 4 } //pass callback function to consume the result getItemNameById(100, displayHelperCallback); //step 1Things to note:1. Async code doesn’t directly ‘return’ anything2. Instead, it takes a function(callback) & calls that function when result becomes available 19
    • Callbacks – Control flow (detailed version in Node.js)//YOUR APPvar db = require(‘db’);function getItemNameById(id, callback) { db.get(id, callback); //step 2}//You create a callback helper functionfunction displayHelperCallback(name) { console.log(name); //step 103}//pass callback function to consume the resultgetItemNameById(100, displayHelperCallback); //step 1 //step 5 V8 is free to run other functions in the event-loop.//INTERNALS OF A DB LIBRARY (HIGH LEVEL)function db() { this.dbConnection = net.connection(); // connects to DB}db.protorype.get = function(id, callback) { var self = this; //step 3 & //step4 is dbConnection.read (below) //step 5, step 6 ..step 100 this.dbConnection.read(id, function(result, callback) { self. receiveFromDB(result, callback);//step 101 Step 5 Say v8 notices 95 other things to do (in the event }); loop), it starts executing them one by one.} At some point b/w step 3 and step 100, returnsdb.protorype.receiveFromDB = function(result, callback) { result & asks to run dbConnection.write’s callback. callback(result); //Execute callback step step 102} This event goes to the back of the queue as step 101 20
    • Node.js ProgrammingHow can I better organize my code? Classes & CommonJS module 21
    • JavaScript Classes (util.inherits) Node.js provides handy util.inherits function to inherit a class. - This also provides ‘subclass.super_’ to access super class’ functions var require(‘util’); //import util module //Super Class function Automobile(license, model) { this.license = license; this.model = model; } Automobile.prototype.getModel = function() { return model; } //Sub class function Car(license, model) { Automobile.call(this, license, model); } util.inherits(Car, Automobile);22
    • CommonJS modules//Automobile.js file Things to note:function Automobile(license, model) { 1. Allows keeping JS code in separate this.license = license; this.model = model; files} 2. Use “exports.<name>” to exportAutomobile.prototype.getModel = function() { something return model;}exports.Automobile = Automobile; 1. Use require(‘path/to/module’) to import it 2. use require(‘module’).<name> to//Car.js file access things inside modulevar util = require(util);var module = require(./Automobile);var Automobile = module.Automobile;function Car(license, model) { Automobile.call(this, license, model);}util.inherits(Car, Automobile);console.log(new Car("1232", "BMW").model); //prints BMW 23
    • CommonJS modules: Exporting multiple things//myModule.js file Things to note:exports.myFunction = function () { 1. You can directly export function, return ‘hi there’;} arrays, variablesexports.myArray = [‘foo’, ‘bar’]; 2. You can export multiple things fromexports.myVariable = ‘I’m a variable’; one file using ‘exports’//app.js filevar myModule = require(./myModule);console.log(myModule.myFunction()); //prints ‘’hi there’console.log(myModule.myArray[1]); //prints ‘bar’console.log(myModule.myVariable); //prints I’m a variable’ 24
    • CommonJS modules: ‘exports’ v/s ‘module.exports’//myModule.js file Things to note:module.exports = function () { If you want to export only one class/ return ‘hi there’;} function.. so that it can be used directly by the recipient, you can use: module.exports = <something>; Warning: If you use both module.exports//app.js file and exports.bla, exports.bla willvar myFunction = require(./myModule); NOT be exported(ignored)console.log(myModule.myFunction()); //prints ‘’hi there’ 25
    • Installing external modules – npm (Node Package Manager) Use npm (Node Package Manager) to install modules npm install <moduleName> e.x. npm install express Modules are copied into ./node_modules folder /myapp /myapp/node_modules/express Things to note: 1. npm = Node Package Manager 2. It is a CLI to install modules from http://search.npmjs.org 3. LOCAL: npm install express 1. It installs in myapp/node_modules/express 4. GLOBAL: npm install express -g 1. It installs in /usr/local/lib/node_modules/ (default) 2. Installs executable files in /usr/local/.bin (default) 5. Use GLOBAL when the library has some shell script & want to reuse it for different apps26
    • Installing external modules - npm & package.json//Instead keep ALL dependencies in Things to note: 1. If you use package.json, you canpackage.json file in root of your app and simply do npm install (w/o anyrun: module names)npm install 2. Keep package.json in root directory//package.json 3. Using package.json is preferred over{ individual npm install <module> "name": "MyApp", "description": "My awesome twitter app", 4. You need to have all the modules pre- "version": "2.5.8", installed (i.e. npm install) before uploading your app to Cloud Foundry "author": "Raja <rajar@vmware.com>", "dependencies": { "express": "2.3.4", "mime": "", "connect-redis": ">= 0.0.1" }}27
    • Node.js EventEmitter (A utility class that allows emitting events) EventEmitter class implements the Observer pattern, and provides on and emit APIs - It is used when creating (not using) an async library. Node.js EventEmitter28
    • Events – Node.js EventEmitter (A node.js utility class that allows emitting events)//Simplified EventEmitter (Observer pattern)function EventEmitter() { //store events and callbacks like {event1: [callback1, callback2] , event2 : [cb3, cb4]…} this.eventNameAndCallbackList = {};}//Allow others to add a callback(function) for a event name(string)EventEmitter.prototype.on = function(eventName, callback) { //add eventName and callback to eventNameAndCallbackList};//When an event is emitted, call each callbacks in a loopEventEmitter.prototype.emit = function(eventName) { for(var i =0; i < currentCallbacks.length ; i++) { currentCallbacks[i](); //call each callback }};exports.EventEmitter = EventEmitter; 29
    • Events – Node.js EventEmitter (continued)Say you are writing an I/O library & writing readFromDB function but don’t know how to handleasync DB result.You can solve it by..1. Inheriting your class from EventEmitter2. Then you can use its ‘emit’ function to an event when data arrives (asynchronously)3. You ask people who’ll be using your library to implement ‘on’ function //myIOModule.js var util = require(util); var events = require(events); //myIOClass is a subclass of events.EventEmitter class var MyIOClass = function () { events.EventEmitter.call(this); }; util.inherits(MyIOClass, events.EventEmitter); MyIOClass.prototype.readFromDB = function(query){ // <--reads data code here --> this.emit(data, "some data"); } exports.MyIOClass = MyIOClass; //export the class30
    • Events – Node.js EventEmitter (continued)Say you are an end-user trying to use DB library to read result from DB..1. You’ll have to implement ‘on’ function for the given event name (‘data’) and set a callback2. DB libraries internal function will call your callback when the result comes back //app.js var myIOModule = require(./myIOModule); var myIOClass = new myIOModule.MyIOClass(); myIOClass.on(data, function (data) { console.log(data); }); myIOClass.readFromDB(select * from users);31
    • Events – A library can emit multiple events I/O libraries usually emit multiple events.. connected, disconnected, error, ready, data, result etc. //So you can listen to all of them.. function myFunction() { db.on(‘error’, function(e) { console.error(e); }); db.on(‘connect’, function() { //db is connected db.query(user); }); db.on(‘disconnect’, function(){ console.log(‘db disconnected’); }); db.connect(‘127.0.0.1’, ‘100’); }32
    • Events – Error/Exception handling //Say there was an exception trying to connect to db. Function () { try { db.connect(‘127.0.0.1’, ‘4000’); // failed to connect; connectionException } catch (e) { console.error(e); } } Above try/catch won’t handle it because the act of connection itself is an i/o //Say there was an exception trying to connect to db. Function () { //Typically I/O libraries triggers ‘error’ event (or callback). We’ll need to listen to that event db.on(‘error’, function(e) { console.error(e); }); db.connect(‘127.0.0.1’, ‘100’); // failed to connect; connectionException }33
    • Agenda – part 31. About Node.js • Internal working of Node.js • Buzz around Node.js • Who is using it • What kind of apps are being built2. Coding in Node.js • Sync v/s Async coding (Callbacks) • Classes & Modules (CommonJS) • npm & package.json • Node.js EventEmitters3. Node.js & Cloud Foundry (w/ demo) • Hello World app in Cloud Foundry • Using Sticky Sessions • CloudFoundry Module & connecting to Redis, MongoDB etc. • Express.js (RESTful) app • Socket.io + Express.js (Real-time) app34
    • Cloud Foundry Cloud Foundry – Open Platform as a Service35
    • Cloud Foundry open Platform as a ServiceThe PaaS of choice for the Cloud eraSimple • Lets developers focus on their code and not wiring middlewareOpen • Avoid lock-in to specific cloud, frameworks or service • Completely Open Source from day oneFlexible and Scalable • Self service, deploy and scale your applications in seconds • Extensible architecture to “digest” future cloud innovation36
    • Cloud Foundry open PaaS - Choice of frameworks OSS community
    • Cloud Foundry open PaaS - Choice of application servicesvFabricPostgres Ap plica Data Services o n *S vFabric RabbitMQTM erv Msg Services ice *In ter fac Other e Services Additional partners services …
    • Cloud Foundry open PaaS - Choice of clouds Av oid Loc k-in e Ap fac Private* p ter lica Data Services Clouds* r*In o ide n *S ov erv Public *Pr Msg Services ice Clouds Partners ud *In Cl o ter .COM Micro fac Other e Services Clouds
    • Node.js & Cloud Foundry (Demos and Examples)40
    • Hello World App on Cloud Foundry//Simple http server on localhost //Simple http server on Cloud Foundryvar http = require(http); var http = require(http);http.createServer(function (req, res) { var host = process.env.VCAP_APP_HOST || ‘localhost’; res.writeHead(200, {Content-Type: text/plain}); var port = process.env.VCAP_APP_PORT || ‘3000’; res.end(Hello Worldn); http.createServer(function (req, res) {}).listen(3000, 127.0.0.1); res.writeHead(200, {Content-Type: text/plain});console.log(Server running at 127.0.0.1:3000); res.end(Hello Worldn); }).listen(port, host); console.log(Server running at ’ + host + “:” + port); Things to note: 1. Cloud Foundry will provide host and port info in process.env variable 2. You can use https to access your app (up to nginx; http w/in CF) 3. Save your app as app.js or server.js to automatically use that as main node.js and have it recognised by vmc push deployment 41
    • “cloudfoundry” module & Connecting to MongoDB, Redis Connecting to services42
    • “cloudfoundry” NodeJS helper modulenpm install cloudfoundryvar cloudfoundry = require(‘cloudfoundry’);cloudfoundry.cloud //is running on Cloud Foundry?cloudfoundry.host // hostcloudfoundry.port // port//Example: Say you are using ‘test-mongodb’ MongoDB service, you can get its info:cloudfoundry.mongodb[test-mongodb].credentials.hostnamecloudfoundry.mongodb[test-mongodb].credentials.portcloudfoundry.mongodb[test-mongodb].credentials.dbcloudfoundry.mongodb[test-mongodb].credentials.usernamecloudfoundry.mongodb[test-mongodb].credentials.password Things to note: 1. cloudfoundry module (built by ‘igo’) provides easy access to environment variables 2. For more, please go through https://github.com/cloudfoundry-samples/cloudfoundry43
    • MongoDB – Example of inserting a user (using mongodb-native module) var mongodb = require(mongodb).Db; var conn; // holds connection //connect to db and get connection obj //connectionUrl looks like mongodb://username:pwd@host:port/dbName mongodb.connect(connectionUrl, function(err, connection) { conn = connection; } //add a user function addUser (userObj, callback) { //Get the collection that holds users conn.collection(users, function (err, userCollection) { //insert user to this collection userCollection.insert(userObj, {safe:true}, function(err) { callback(userObj); }); }); } //PS: Error handling is not shown44
    • Demo app Things to note: 1. Simple MongoDB demo app, adds random users and pulls existing users 2. https://github.com/rajaraodv/mongoapp145
    • ExpressJS46
    • Hello World App using ExpressJSvar host = process.env.VCAP_APP_HOST || localhost;var port = process.env.VCAP_APP_PORT || 3000; Things to note: 1. ExpressJS is a Ruby Sinatravar express = require(express);var app = express.createServer(); inspired web frameworkapp.listen(port, host); 2. Built on top of ‘Connect’ – which itself is a wrapper for http-module 3. Provides support for: 1. Dev/Prod Configurations 2. Routes 3. Templating 4. Sessions 5. Many, many other features47
    • Hello World App using ExpressJS (Middlewares) var express = require(express); var app = express.createServer(); //Middlewares app.use(express.logger()); //logs requests app.use(express.static(__dirname + ‘/public’)); //sets location of public files app.use(express.bodyParser()); //parses HTTP POST body Things to Note: 1. Middlewares are functions that helps in common tasks involved building in web applications 2. They are actually connect-module functions but exposed by ExpressJS for simplicity48
    • Hello World App using ExpressJS (Environments) var express = require(express); var app = express.createServer(); app.configure(development, function() { //On error, print exceptions to console & to the web-page itself app.use(express.errorHandler({ dumpExceptions: true, showStack: true })); }); app.configure(production, function() { //On error, this simply says ‘Internal error Occurred’ app.use(express.errorHandler({ dumpExceptions: true, showStack: false })); app.use(express.logger()); //logs requests }); Things to Note: 1. Express uses NODE_ENV environment variable to set working environment 2. On CF, to toggle b/w ‘development’ and ‘production’, you can use.. vmc env-add <appName> NODE_ENV ‘production’49
    • Hello World App using ExpressJS (Routing)var express = require(express); Things to note:var app = express.createServer(); 1. You can use Routing to listenapp.use(express.bodyParser()); to requests to call different functions//Receive HTTP GETapp.get(/user, function(req, res) { 2. You can listen to HTTP POST, //Don’t let people call to /user PUT etc. throw new Error(“I’m private. Call me w/ a user id");});app.get(/user/:id, function(req, res){ res.send(user + req.params.id);});//Receive HTTP POSTapp.post(‘’/register”, function(req, res) { //(Use bodyParser middleware for this) var body = req.body; db.save(body.user, body.password);}50
    • Hello World App using ExpressJS (Sessions) var express = require(express); var app = express.createServer(); //Middlewares app.use(express.static(__dirname + ‘/public’)); //sets location of public files app.use(express.bodyParser()); //parses HTTP POST body app.use(express.cookieParser()); //Parses cookies headers app.use(express.session({secret: your secret here})); Things to note: 1. To create sessions, use cookieParser & session middlewares 2. By default Express uses MemoryStore to store sessions 3. You can use Redis to store sessions51
    • ExpressJS (Sticky sessions for multi instances) var express = require(express); var app = express.createServer(); //Middlewares app.use(express.static(__dirname + ‘/public’)); //sets location of public files app.use(express.bodyParser()); //parses HTTP POST body app.use(express.cookieParser()); //Parses cookies headers app.use(express.session({secret: your secret here’, key: ‘jsessionid’ })); Things to note: 1. Sticky Session is a reverse proxy / load balancer feature to help persistent connection 2. When Sticky Session is on, request goes from Nginx to the same instance no matter how many instances of your app is running . 3. Cloud Foundry’s Nginx provides Sticky Sessions on ‘jsessionid’ cookie 4. W/o setting this requests are randomly sent to different instances & you’ll have to use external store like Redis to fetch session data (recommended).52
    • ExpressJS (demo)53
    • ExpressJS demo app screenshots (routing, sessions & sticky sessions) Demo Explains how session, sticky sessions, routing etc. works For more: https://github.com/rajaraodv/express154
    • Socket.io on Cloud Foundry Socket.io55
    • Socket.io on Cloud Foundry (server side) var sio = require(socket.io); var express = require(express); var app = express.createServer(); var io = sio.listen(app);//listen to express io.configure(function() { io.set(log level, 1); io.set("transports", ["xhr-polling"]); //Currently CF doesn’t support websockets }); Things to Note: 1. Socket.io is mainly used to build real-time apps 2. Socket.io provides a single interface to switch b/w various transport techniques like xhr-polling, websocket, JSONP etc 3. In addition, it provides heartbeats, reconnection, timeouts etc. that are vital for real-time apps. 4. It works seamlessly with ExpressJS56
    • Socket.io on Cloud Foundry (server side continued) //After listening to express..wait for connection from browser io.sockets.on(connection, function(socket) { // When the client/browser emits sendchat, this listens and executes socket.on(sendchat, function(data) { // We will echo it back to ALL sockets io.sockets.emit(updatechat’, data); }); });57
    • Socket.io on Cloud Foundry (client side)<script src="/socket.io/socket.io.js"></script>//socket.io serves this file from servervar socket = io.connect(document.location.href); //connect to the server // on connection socket.on(connect, function() { console.log("client connected"); }); // Whenever the server emits updatechat, this updates the chat body socket.on(updatechat, function (data) { $(#conversation).append(data); // append it to my list }); //When the user enter some data, send it to server function sendchat() { var message = $(#chatField).val(); // Emit or tell server to execute sendchat’ socket.emit(sendchat, message); }58
    • Socket.io (+ ExpressJS) Demo app screenshots For more: https://github.com/rajaraodv/socketio159
    • Simple coding and deployment - Cloud9 IDE60
    • Summary1. About Node.js • Internal working of Node.js • Buzz around Node.js • Who is using it • What kind of apps are being built2. Coding in Node.js • Sync v/s Async coding (Callbacks) • Classes & Modules (CommonJS) • npm & package.json • Node.js EventEmitters3. Node.js & Cloud Foundry (w/ demo) • Hello World app in Cloud Foundry • Using Sticky Sessions • CloudFoundry Module & connecting to Redis, MongoDB etc. • Express.js (RESTful) app • Socket.io + Express.js (Real-time) app61
    • Questions? Questions? @rajaraodv (github.com/rajaraodv) @andypiper (github.com/andypiper) @cloudfoundry (github.com/cloudfoundry)62