© 2009 VMware Inc. All rights reserved

Becoming a Node.js ninja onCloud Foundry

March 2012

Patrick Chanezon, Senior Director, Developer Relationschanezonp@vmware.com, @chanezonWith slides from Raja Rao DV

www.cloudfoundry.com

Wednesday, March 28, 12

P@ in a nutshell

• French, based in San Francisco

• Senior Director, Developer Relations, VMware

• Software Plumber, API guy, mix of Enterprise and Consumer

• 18 years writing software, backend guy with a taste for javascript

• 2 y Accenture (Notes guru), 3 y Netscape/AOL (Servers, Portals), 5 y Sun (ecommerce, blogs, Portals, feeds, open source)

• 6 years at Google, API guy (first hired, helped start the team)

• Adwords, Checkout, Social, HTML5, Cloud

Wednesday, March 28, 12

3

Sketching Things

Slender clouds. On the pavilion a small rain.Noon, but I’m too lazy to open the far cloister.I sit looking at moss so green my clothes are soaked with color.

Wang Wei (699-759)

Wednesday, March 28, 12

4

Taking a Nap by a Mountain Window

Resting my body in a monk’s cloud chamber, my dreams relax.Pine trees and cranes rise between screen and pillow.A beautiful pheasant makes a long song.My hand pushes the window, and the mountain fill my eyes.

Zhu Yunming (1461-1527)

Wednesday, March 28, 12

5

Looking for the Hermit and Not Finding Him

Beneath a pine I question a boy.He says, “Master has gone to gather herbs somewhere on the mountainbut who knows where? The clouds are deep.”

Jiao Dao (778-841)

Wednesday, March 28, 12

6

Looking for the Hermit and Not Finding Him

Lu mountain stands beside the Southern DipperIn clouds reaching silken like a nine-panelled screenWith its shadows in a crystal lake deepening the green water.The Golden Gate opens into two mountain ranges.

Li Bai (701-762)

Wednesday, March 28, 12

7

Agenda

1. About Node.js• Internal working of Node.js• Buzz around Node.js• Who is using it• What kind of apps are being built

2. Coding in Node.js• Sync v/s Async coding (Callbacks)• Classes & Modules (CommonJS)• Node.js EventEmitters • npm & package.json

3. 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) app

4. Final demo• An sample app that uses concepts & modules talked above

Wednesday, March 28, 12

8

About Node.js

Node.js is a non-blocking, event-driven I/O platform that is built onGoogle Chrome’s v8 engine.

- 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)

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9

What is the biggest advantage of Node.js?

Biggest thing Node.js brings to the table (other than JS) is savings in I/O cost

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10

The cost of I/O

http://blog.mixu.net/2011/02/01/understanding-the-node-js-event-loop/

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11

So how does Node.js save I/O cost?

Node.js saves I/O cost by implementingNon-blocking, event driven I/O model

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12

Event-driven, non-blocking I/O platform/server

Multi-threaded blocking server v/s

Event-driven, non-blocking server

What exactly is a event-driven, non-blocking server?

How is it different from a multi-threaded server?

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13

Multi-threaded server - Threads are spawned for every connection

Multi threadedserver

DB

FS

T Thread

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Multi-threaded server - Threads are spawned for every connection

Multi threadedserver

User1

DB

FS

T Thread

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Multi-threaded server - Threads are spawned for every connection

Multi threadedserver

User1 i/o request

DB

FS

T Thread

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Multi-threaded server - Threads are spawned for every connection

Multi threadedserver

T1User1 i/o request

DB

FS

T Thread

Wednesday, March 28, 12

13

Multi-threaded server - Threads are spawned for every connection

Multi threadedserver

T1User1 i/o request

DB

Blocking

FS

T Thread

Wednesday, March 28, 12

13

Multi-threaded server - Threads are spawned for every connection

Multi threadedserver

T1User1

User2

i/o request

DB

Blocking

FS

T Thread

Wednesday, March 28, 12

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Multi-threaded server - Threads are spawned for every connection

Multi threadedserver

T1User1

User2

i/o request

i/o request

DB

Blocking

FS

T Thread

Wednesday, March 28, 12

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Multi-threaded server - Threads are spawned for every connection

Multi threadedserver

T1

T2

User1

User2

i/o request

i/o request

DB

Blocking

FS

T Thread

Wednesday, March 28, 12

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Multi-threaded server - Threads are spawned for every connection

Multi threadedserver

T1

T2

User1

User2

User3Refreshes 2 times

i/o request

i/o request

DB

Blocking

FS

T Thread

Wednesday, March 28, 12

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Multi-threaded server - Threads are spawned for every connection

Multi threadedserver

T1

T2

User1

User2

User3Refreshes 2 times

i/o request

i/o request

DB

Blocking

FS

T Thread

Wednesday, March 28, 12

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Multi-threaded server - Threads are spawned for every connection

Multi threadedserver

T1

T2

T3

User1

User2

User3Refreshes 2 times

i/o request

i/o request

DB

Blocking

FS

T Thread

Wednesday, March 28, 12

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Multi-threaded server - Threads are spawned for every connection

Multi threadedserver

T1

T2

T3

User1

User2

User3Refreshes 2 times

i/o request

i/o request

DB

Blocking

FS

T Thread

Wednesday, March 28, 12

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Multi-threaded server - Threads are spawned for every connection

Multi threadedserver

T1

T2

T3 T4

User1

User2

User3Refreshes 2 times

i/o request

i/o request

DB

Blocking

FS

T Thread

Wednesday, March 28, 12

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Multi-threaded server - Threads are spawned for every connection

Multi threadedserver

T1

T2

T3 T4

User1

User2

User3Refreshes 2 times

i/o request

i/o request

DB

Blocking

FS

T Thread

Wednesday, March 28, 12

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Multi-threaded server - Threads are spawned for every connection

Multi threadedserver

T1

T2

T3 T4 T5

User1

User2

User3Refreshes 2 times

i/o request

i/o request

DB

Blocking

FS

T Thread

Wednesday, March 28, 12

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Multi-threaded server - Threads are spawned for every connection

Multi threadedserver

T1

T2

T3 T4 T5

User4 refreshes 3 times

User1

User2

User3Refreshes 2 times

i/o request

i/o request

DB

Blocking

FS

T Thread

Wednesday, March 28, 12

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Multi-threaded server - Threads are spawned for every connection

Multi threadedserver

T1

T2

T3 T4 T5

T6User4 refreshes 3 times

User1

User2

User3Refreshes 2 times

i/o request

i/o request

DB

Blocking

FS

T Thread

Wednesday, March 28, 12

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Multi-threaded server - Threads are spawned for every connection

Multi threadedserver

T1

T2

T3 T4 T5

T6User4 refreshes 3 times

User1

User2

User3Refreshes 2 times

i/o request

i/o request

DB

Blocking

FS

T Thread

Wednesday, March 28, 12

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Multi-threaded server - Threads are spawned for every connection

Multi threadedserver

T1

T2

T3 T4 T5

T6User4 refreshes 3 times

User1

User2

User3Refreshes 2 times

i/o request

i/o request

DB

Blocking

FS

T Thread

Wednesday, March 28, 12

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Multi-threaded server - Threads are spawned for every connection

Multi threadedserver

T1

T2

T3 T4 T5

T6 T7 T8 T9User4 refreshes 3 times

User1

User2

User3Refreshes 2 times

i/o request

i/o request

DB

Blocking

FS

T Thread

Wednesday, March 28, 12

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Multi-threaded server - Threads are spawned for every connection

Multi threadedserver

T1

T2

T3 T4 T5

T6 T7 T8 T9User4 refreshes 3 times

User1

User2

User3Refreshes 2 times

i/o request

i/o request

DB

BlockingI/O

FS

T Thread

Wednesday, March 28, 12

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Multi-threaded server - Threads are spawned for every connection

Multi threadedserver

T1

T2

T3 T4 T5

T6 T7 T8 T9User4 refreshes 3 times

User1

User2

User3Refreshes 2 times

i/o request

i/o request

DB

BlockingI/O

FS

T Because every I/o is blocking,server spawns a thread per connectionto support multiple requests

Thread

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Non-blocking & Evented I/O (Node.js server)

Node.js

DB

FS

LibioPOSIXAsync

Threadst3

t1t2

t4

t5

t6

T1V8

Event loop(Libev)

Singlethreadserves all users

T1V8

JS Thread running your code (Single threaded)

t3

t1t2 POSIX threads doing

async I/O (multi-threaded)

t7

JS C/C++

Wednesday, March 28, 12

14

Non-blocking & Evented I/O (Node.js server)

Node.js

DB

FS

LibioPOSIXAsync

Threadst3

t1t2

t4

t5

t6

Event loop(Libev)

Singlethreadserves all users

T1V8

JS Thread running your code (Single threaded)

t3

t1t2 POSIX threads doing

async I/O (multi-threaded)

t7

JS C/C++

Wednesday, March 28, 12

14

Non-blocking & Evented I/O (Node.js server)

Node.js

DB

FS

LibioPOSIXAsync

Threadst3

t1t2

t4

t5

t6

Event loop(Libev)

Singlethreadserves all users

T1V8

T1V8

JS Thread running your code (Single threaded)

t3

t1t2 POSIX threads doing

async I/O (multi-threaded)

t7

JS C/C++

Wednesday, March 28, 12

14

Non-blocking & Evented I/O (Node.js server)

Node.js

DB

FS

LibioPOSIXAsync

Threadst3

t1t2

t4

t5

t6

Event loop(Libev)

Singlethreadserves all users

T1V8

JS Thread running your code (Single threaded)

t3

t1t2 POSIX threads doing

async I/O (multi-threaded)

t7

JS C/C++

Wednesday, March 28, 12

14

Non-blocking & Evented I/O (Node.js server)

Node.js

DB

FS

LibioPOSIXAsync

Threadst3

t1t2

t4

t5

t6

Event loop(Libev)

Singlethreadserves all users

T1V8T1

V8JS Thread running your code (Single threaded)

t3

t1t2 POSIX threads doing

async I/O (multi-threaded)

t7

JS C/C++

Wednesday, March 28, 12

14

Non-blocking & Evented I/O (Node.js server)

Node.js

DB

FS

LibioPOSIXAsync

Threadst3

t1t2

t4

t5

t6

Event loop(Libev)

Singlethreadserves all users

T1V8

JS Thread running your code (Single threaded)

t3

t1t2 POSIX threads doing

async I/O (multi-threaded)

t7

JS C/C++

Wednesday, March 28, 12

14

Non-blocking & Evented I/O (Node.js server)

Node.js

DB

FS

LibioPOSIXAsync

Threadst3

t1t2

t4

t5

t6

Event loop(Libev)

Singlethreadserves all users

T1V8

T1V8

JS Thread running your code (Single threaded)

t3

t1t2 POSIX threads doing

async I/O (multi-threaded)

t7

JS C/C++

Wednesday, March 28, 12

14

Non-blocking & Evented I/O (Node.js server)

Node.js

DB

FS

LibioPOSIXAsync

Threadst3

t1t2

t4

t5

t6

Event loop(Libev)

Singlethreadserves all users

T1V8

JS Thread running your code (Single threaded)

t3

t1t2 POSIX threads doing

async I/O (multi-threaded)

t7

JS C/C++

Wednesday, March 28, 12

14

Non-blocking & Evented I/O (Node.js server)

Node.js

DB

FS

LibioPOSIXAsync

Threadst3

t1t2

t4

t5

t6

Event loop(Libev)

Singlethreadserves all users

T1V8

T1V8

JS Thread running your code (Single threaded)

t3

t1t2 POSIX threads doing

async I/O (multi-threaded)

t7

JS C/C++

Wednesday, March 28, 12

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Non-blocking & Evented I/O (Node.js server)

Node.js

DB

FS

LibioPOSIXAsync

Threadst3

t1t2

t4

t5

t6

Event loop(Libev)

Singlethreadserves all users

T1V8

JS Thread running your code (Single threaded)

t3

t1t2 POSIX threads doing

async I/O (multi-threaded)

t7

JS C/C++

Wednesday, March 28, 12

14

Non-blocking & Evented I/O (Node.js server)

Node.js

DB

FS

LibioPOSIXAsync

Threadst3

t1t2

t4

t5

t6

Event loop(Libev)

Singlethreadserves all users

T1V8

T1V8

JS Thread running your code (Single threaded)

t3

t1t2 POSIX threads doing

async I/O (multi-threaded)

t7

JS C/C++

Wednesday, March 28, 12

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Non-blocking & Evented I/O (Node.js server)

Node.js

User1 i/o request DB

FS

LibioPOSIXAsync

Threadst3

t1t2

t4

t5

t6

Event loop(Libev)

Singlethreadserves all users

T1V8

T1V8

JS Thread running your code (Single threaded)

t3

t1t2 POSIX threads doing

async I/O (multi-threaded)

t7

JS C/C++

Wednesday, March 28, 12

14

Non-blocking & Evented I/O (Node.js server)

Node.js

User1 i/o request DB

Non-blockingI/O

FS

LibioPOSIXAsync

Threadst3

t1t2

t4

t5

t6

Event loop(Libev)

Singlethreadserves all users

delegate i/o tolibeio

T1V8

T1V8

JS Thread running your code (Single threaded)

t3

t1t2 POSIX threads doing

async I/O (multi-threaded)

t7

JS C/C++

Wednesday, March 28, 12

14

Non-blocking & Evented I/O (Node.js server)

Node.js

User1

User2

i/o request DB

Non-blockingI/O

FS

LibioPOSIXAsync

Threadst3

t1t2

t4

t5

t6

Event loop(Libev)

Singlethreadserves all users

i/o request

delegate i/o tolibeio

T1V8

T1V8

JS Thread running your code (Single threaded)

t3

t1t2 POSIX threads doing

async I/O (multi-threaded)

t7

JS C/C++

Wednesday, March 28, 12

14

Non-blocking & Evented I/O (Node.js server)

Node.js

User1

User2

i/o request DB

Non-blockingI/O

FS

LibioPOSIXAsync

Threadst3

t1t2

t4

t5

t6

Event loop(Libev)

Singlethreadserves all users

i/o request

delegate i/o tolibeio

T1V8

JS Thread running your code (Single threaded)

t3

t1t2 POSIX threads doing

async I/O (multi-threaded)

t7

JS C/C++

Wednesday, March 28, 12

14

Non-blocking & Evented I/O (Node.js server)

Node.js

User1

User2

i/o request DB

Non-blockingI/O

FS

LibioPOSIXAsync

Threadst3

t1t2

t4

t5

t6

Event loop(Libev)

Singlethreadserves all users

i/o request

delegate i/o tolibeio

T1V8

T1V8

JS Thread running your code (Single threaded)

t3

t1t2 POSIX threads doing

async I/O (multi-threaded)

t7

JS C/C++

Wednesday, March 28, 12

14

Non-blocking & Evented I/O (Node.js server)

Node.js

User1

User2

User3Refreshes 2 times

i/o request DB

Non-blockingI/O

FS

LibioPOSIXAsync

Threadst3

t1t2

t4

t5

t6

Event loop(Libev)

Singlethreadserves all users

i/o request

delegate i/o tolibeio

T1V8

T1V8

JS Thread running your code (Single threaded)

t3

t1t2 POSIX threads doing

async I/O (multi-threaded)

t7

JS C/C++

Wednesday, March 28, 12

14

Non-blocking & Evented I/O (Node.js server)

Node.js

User1

User2

User3Refreshes 2 times

i/o request DB

Non-blockingI/O

FS

LibioPOSIXAsync

Threadst3

t1t2

t4

t5

t6

Event loop(Libev)

Singlethreadserves all users

i/o request

delegate i/o tolibeio

T1V8

T1V8

JS Thread running your code (Single threaded)

t3

t1t2 POSIX threads doing

async I/O (multi-threaded)

i/o result returned 2 EL after x time

t7

JS C/C++

Wednesday, March 28, 12

14

Non-blocking & Evented I/O (Node.js server)

Node.js

User4 refreshes 3 times

User1

User2

User3Refreshes 2 times

i/o request DB

Non-blockingI/O

FS

LibioPOSIXAsync

Threadst3

t1t2

t4

t5

t6

Event loop(Libev)

Singlethreadserves all users

i/o request

delegate i/o tolibeio

T1V8

T1V8

JS Thread running your code (Single threaded)

t3

t1t2 POSIX threads doing

async I/O (multi-threaded)

i/o result returned 2 EL after x time

t7

JS C/C++

Wednesday, March 28, 12

14

Non-blocking & Evented I/O (Node.js server)

Node.js

User4 refreshes 3 times

User1

User2

User3Refreshes 2 times

i/o request DB

Non-blockingI/O

FS

LibioPOSIXAsync

Threadst3

t1t2

t4

t5

t6

Event loop(Libev)

Singlethreadserves all users

i/o request

delegate i/o tolibeio

T1V8

T1V8

JS Thread running your code (Single threaded)

t3

t1t2 POSIX threads doing

async I/O (multi-threaded)

i/o result returned 2 EL after x time

t7

Everything except your (JS) code is runs in parallel (by libio)

JS C/C++

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Event-driven, non-blocking I/O server

Multi-threaded blocking server (Apache) v/s

Event-driven, non-blocking server (Nginx)

Real-world example of the two models?

Wednesday, March 28, 12

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Apache V/s Nginx: performance

Ref: http://blog.webfaction.com/a-little-holiday-present

Reqs/sec v/s concurrent connections

At ~4000 concurrent connections, - Nginx can serve ~9000 reqs/sec - Apache can serve ~3000 reqs/sec

Wednesday, March 28, 12

17

Apache V/s Nginx: Memory usage

Ref: http://blog.webfaction.com/a-little-holiday-present

Memory v/s concurrent connections

At ~4000 concurrent connections, - Nginx uses 3MB memory- Apache uses 40MB memory

Wednesday, March 28, 12

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Saving I/O is great, what else is happening w/ Node.js?

Let’s look at community, libraries, buzz around Node.js

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Other things going on for Node.js

2nd most popular watched on git

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Other things going on for Node.js

8,000+ libraries/modules/servers

Web frameworksRoutersStatic file serversMicroframeworksFrameworksMiddlewareJSGIConnectOther middlewareOtherDatabaseMS SQL ServerPostgreSQLMySQLSQLite

OracleNoSQL and Key/ValueMongoHiveRedisCouchDBOther NoSQL implementationsMiscellaneous and multiple DBTemplatingCSS EnginesContent Management SystemsBuild and DeploymentPackage Management SystemsModule LoaderOpenSSL / Crypto / HashingSMTPTCP / IP

Multiple protocolsHTTPFTPE-mailXMPPOther networkingRPCWeb Sockets & AjaxMessage QueuesClass systemsTesting / Spec FrameworksWrappersParsersJSONXML

Command Line Option ParsersParser GeneratorsOther ParsersDebugging / Console UtilitiesCompressionGraphicsSoundPayment GatewaysAPI clientsControl flow / Async goodiesI18n and L10n modulesBoilerplatesContinuous Integration ToolsDDD, CQRS, EventSourcingDesktop application relatedJavaScript threadsOther

High-level library categories

https://github.com/joyent/node/wiki/modules

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Other things going on for Node.js

Node in Production!• LinkedIn, Yahoo!, Microsoft, 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 – - Node.js implementation of LDAP server itself• SMTP – Node.js implementation of SMTP server itself• XMPP, SSH, RPC, many more.

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Agenda – part 2

1. About Node.js• Internal working of Node.js• Buzz around Node.js• Who is using it• What kind of apps are being built

2. Coding in Node.js• Sync v/s Async coding (Callbacks)• Classes & Modules (CommonJS)• Node.js EventEmitters• npm & package.json

3. Node.js & Cloud Foundry• 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) app

4. Demo• An sample app that uses concepts & modules talked above

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Let’s look at the code..

Synchronous codev/s

Asynchronous Code

How does async code differ from sync(regular) code?

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Callbacks – Control flow

//Synchronous & blocking codefunction getItemNameById(id) { //blocks or waits for DB return db.get(id); //step 2}

var name = getItemNameById(100); //step 1

//print name in step 3console.log(name); //step 3

//Async & non-blocking code function getItemNameById(id, callback) { db.get(id, callback); //step 2 //nothing is returned here}

//step 3Some internal function calls the callback w/ result

//You create a callback helper function function displayHelperCallback(name) { console.log(name); //step 4}

//pass callback function to consume the resultgetItemNameById(100, displayHelperCallback); //step 1

Things to note:1. Async code doesn’t directly ‘return’

anything2. Instead, it takes a function(callback)

& calls that function when result becomes available

Use case: Let’s say we have an item’s id and want to get its name from DB and print it

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Callbacks – Control flow (detailed version in Node.js)

//INTERNALS OF A DB LIBRARY (HIGH LEVEL)

function db() { this.dbConnection = net.connection(); // connects to DB}db.prototype.get = function(id, callback) { var self = this; //step 3 this.dbConnection.write(id, function(result) { //step 4 self. receiveFromDB(result, callback);//step 101 }); }

db.prototype.receiveFromDB = function(result, callback) { callback(result); //Execute callback step step 102 }

//YOUR APPvar db = require(‘db’);function getItemNameById(id, callback) { db.get(id, callback); //step 2}

//You create a callback helper function function displayHelperCallback(name) { console.log(name); //step 103}

//pass callback function to consume the resultgetItemNameById(100, displayHelperCallback); //step 1

//step 5V8 is free to run other functions in the event-loop.

//step 5, step 6 ..step 100Say 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, returns result & asks to run dbConnection.write’s callback.

This event goes to the back of the queue as step 101

Step 5

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Node.js

Classes & CommonJS module

How can I better organize my code?

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JavaScript Classes (Prototypical inheritance)

//JavaScript prototypical inheritance

//Super Classfunction Automobile(license, model) { this.license = license; this.model = model;}

Automobile.prototype.getModel = function() { return model;}

//Sub classfunction Car(license, model) { Automobile.call(this, license, model);}

Car.prototype = new Automobile();Car.prototype.constructor = Car;

Node.js also provides handy util.inherits function to inherit.- This also provides ‘subclass.super_’ to access

super class’ functions

var require(‘util’); //import util module

//Super Classfunction Automobile(license, model) { this.license = license; this.model = model;}

Automobile.prototype.getModel = function() { return model;}

//Sub classfunction Car(license, model) { Automobile.call(this, license, model);}

util.inherits(Car, Automobile);

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CommonJS modules

//Automobile.js filefunction Automobile(license, model) { this.license = license; this.model = model;}

Automobile.prototype.getModel = function() { return model;}exports.Automobile = Automobile;

//Car.js filevar 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

Things to note:1. Allows keeping JS code in separate

files

2. Use “exports.<name>” to export something

1. Use require(‘path/to/module’) to import it

2. use require(‘module’).<name> to access things inside module

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CommonJS modules: Exporting multiple things

//myModule.js fileexports.myFunction = function () { return ‘hi there’;}exports.myArray = [‘foo’, ‘bar’];

exports.myVariable = ‘I’m a variable’;

//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’

Things to note:1. You can directly export function,

arrays, variables

2. You can export multiple things from one file using ‘exports’

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CommonJS modules: ‘exports’ v/s ‘module.exports’

//myModule.js filemodule.exports = function () { return ‘hi there’;}

//app.js filevar myFunction = require('./myModule');

console.log(myModule.myFunction()); //prints ‘’hi there’

Things to note:If you want to export only one thing.. so that it can be used directly by the recepient, you can use..module.exports = <something>;

Warning:If you use both module.exports and exports.bla, exports.bla will NOT be exported(ignored)

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31

Node.js EventEmitter (A utility class that allows emitting events)

Node.js EventEmitter

EventEmitter class implements Observer pattern and provides on and emit APIs • It is used when creating(not using) an async library.

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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;

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Events – Node.js EventEmitter (continued)

//myIOModule.jsvar util = require('util');var events = require('events');

//myIOClass is a subclass of events.EventEmitter classvar 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 class

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 EventEmitter 2. 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

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Events – Node.js EventEmitter (continued)

//app.jsvar myIOModule = require('./myIOModule');

var myIOClass = new myIOModule.MyIOClass();myIOClass.on('data', function (data) { console.log(data);});

myIOClass.readFromDB('select * from users');

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

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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’);}

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36

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. 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}

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37

Installing external modules – npm (Node Package Manager)

Use npm (Node Package Manager) to install modulesnpm install <moduleName>e.x. npm install express

Modules are copied into ./node_modules folder /myapp/myapp/node_modules/express

//Instead keep ALL dependencies in package.json file in root of your app and run:npm install

//package.json{ "name": ”MyApp", "description": ”My awesome twitter app", "version": "2.5.8", "author": ”Raja<rajar@vmware.com>", "dependencies": { "express": “2.3.4”, "mime": "", "connect-redis": ">= 0.0.1" }}

Things to note:1. npm = Node Package Manager2. It is a CLI to install modules from3. Using package.json is preferred

1. Need to be careful about versions

2. You need to have all the modules pre-installed (i.e. npm install) before uploading your app to Cloud Foundry

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38

Installing external modules - npm & package.json

Use npm (Node Package Manager) to install modulesnpm install <moduleName>e.x. npm install express

Modules are copied into ./node_modules folder /myapp/myapp/node_modules/express

//Instead keep ALL dependencies in package.json file in root of your app and run:npm install

//package.json{ "name": ”MyApp", "description": ”My awesome twitter app", "version": "2.5.8", "author": ”Raja<rajar@vmware.com>", "dependencies": { "express": “2.3.4”, "mime": "", "connect-redis": ">= 0.0.1" }}

Things to note:1. npm = Node Package Manager2. It is a CLI to install modules from3. Using package.json is preferred

1. Need to be careful about versions

2. You need to have all the modules pre-installed (i.e. npm install) before uploading your app to Cloud Foundry

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Agenda – part 3

1. About Node.js• Internal working of Node.js• Buzz around Node.js• Who is using it• What kind of apps are being built

2. Coding in Node.js• Sync v/s Async coding (Callbacks)• Classes & Modules (CommonJS)• Node.js EventEmitters• npm & package.json

3. Node.js & Cloud Foundry (w/ demo)• Cloud Foundry – Open PaaS• Hello World app in Cloud Foundry• Scaling - Using Sticky Sessions• CloudFoundry Module & connecting to Redis, MongoDB etc • Express.js (RESTful) app• Socket.io + Express.js (Real-time) app

4. Demo• An sample app that uses concepts & modules talked above

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40

Cloud Foundry

Cloud Foundry – Open Platform as a Service

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What is Cloud Computing?

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Cloud According to my daughter Eliette (10 years old)

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Cloud Stack - Classic Pyramid

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Platform As A Service

Infrastructure As A Service

SoftwareAs A Service

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Cloud Stack - By Value

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InfrastructureAs A Service

SoftwareAs A Service

Platform As A Service

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Agility as a survival skill

§ Consumer software is becoming like fashion•Phone apps, social apps, short lifetime, fast lifecycles

•Ab testing

§ Clay shirky situational apps

§ Kent Beck, Usenix 2011 Talk, “Software G-Forces”change in software process when frequency grows

§ Cloud Platforms enables an Agile culture, driver for innovation•Scalability is built in the platforms

•Can iterate faster

•Focus on design

§ Cloud Platforms lets developers focus on driving business value

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Platforms

§ Raise the Unit of currency to be application & services instead of infrastructure

§ Google App Engine, Cloud Foundry, Joyent, Heroku, Stax (Cloudbees), Amazon elastic beanstalk, Microsoft Azure, AppFog

§ Single or a few languages, services

§ Start of Multi language Polyglot platforms

§ Enabler for Agile Developers -> Create Business value faster

§ Lack of standards: risk, vendor lock-in

§ Enterprise needs:•Control, customizability

•Private/Hybrid Cloud

•Avoid lock-in

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Main Risk: Lock-In

46

Welcome to the hotel californiaSuch a lovely placeSuch a lovely facePlenty of room at the hotel californiaAny time of year, you can find it here

Last thing I remember, I wasRunning for the doorI had to find the passage backTo the place I was before’relax,’ said the night man,We are programmed to receive.You can checkout any time you like,But you can never leave!

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Cloud Foundry open PaaS - Choice of frameworks

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Cloud Foundry open PaaS - Choice of frameworks

OSS community

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Applica'on  Service  Interface

Data Services

Other Services

Msg Services

Cloud Foundry open PaaS - Choice of application services

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Applica'on  Service  Interface

Data Services

Other Services

Msg Services

Cloud Foundry open PaaS - Choice of application services

vFabric Postgres

vFabric RabbitMQTM

Additional partners services …

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Applica'on  Service  Interface

Data Services

Other Services

Msg Services

Cloud Foundry open PaaS - Choice of clouds

Private  Clouds  

PublicClouds

MicroClouds

.COM

PartnersClo

ud  Provide

r  Interface

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Applica'on  Service  Interface

Data Services

Other Services

Msg Services

Cloud Foundry open PaaS - Choice of clouds

Private  Clouds  

PublicClouds

MicroClouds

.COM

PartnersClo

ud  Provide

r  Interface

Avoid

Lock-in

Wednesday, March 28, 12

Applica'on  Service  Interface

Data Services

Other Services

Msg Services

Cloud Foundry open PaaS - Choice of clouds

Private  Clouds  

PublicClouds

MicroClouds

.COM

PartnersClo

ud  Provide

r  Interface

Avoid

Lock-in

OSS community

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Open Source Advantage: it gets better faster!

§ http://code.google.com/p/googleappengine/issues/detail?id=13

50

• https://github.com/cloudfoundry/vcap/pull/25

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51

Cloud Foundry open Platform as a Service

The PaaS of choice for the Cloud era

Simple• Let’s developers focus on their code and not wiring middleware

Open• Avoid lock-in to specific cloud, frameworks or service• Completely open source from day one

Flexible and Scalable• Self service, deploy and scale your applications in seconds• Extensible architecture to “digest” future cloud innovation

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Cloud for Developers: the true path is PaaS!

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53

Node.js on Cloud foundry (Demos and Examples)

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Hello World App on Cloud Foundry

//Simple http server on localhostvar http = require('http');http.createServer(function (req, res) { res.writeHead(200, {'Content-Type': 'text/plain'}); res.end('Hello World\n');}).listen(3000, '127.0.0.1');console.log('Server running at 127.0.0.1:3000');

//Simple http server on Cloud Foundryvar http = require('http');var host = process.env.VCAP_APP_HOST || ‘localhost’;var port = process.env.VCAP_APP_PORT || ‘3000’;http.createServer(function (req, res) { res.writeHead(200, {'Content-Type': 'text/plain'}); res.end('Hello World\n');}).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

variable2. 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

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Hello World App using ExpressJS on Cloud Foundry

var host = process.env.VCAP_APP_HOST || 'localhost';var port = process.env.VCAP_APP_PORT || '3000';

var express = require('express');var app = express.createServer();

app.configure('development', function() { app.use(express.errorHandler({ dumpExceptions: true, showStack: true }));});

app.configure('production', function() { app.use(express.errorHandler());});

app.get('/user/', function(req, res){ throw new Error(“call me w/ a user id");});

app.get('/user/:id', function(req, res){ res.send('user ' + req.params.id);});app.listen(port, host);

Things to note:1. ExpressJS is Ruby Sinatra

inspired web framework2. It provides support for:

1. Dev/Prod Configurations2. Routes3. Templating4. Sessions5. Many, many other features

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Hello World App w/ built-in node.js cluster ( > 0.6)

var cluster = require('cluster');var http = require('http');var numCPUs = require('os').cpus().length;var port = process.env.VCAP_APP_PORT || 3000;var host = process.env.VCAP_APP_HOST || 'localhost';

if (cluster.isMaster) { //fork workersfor (var i = 0; i < numCPUs; i++) { cluster.fork(); } cluster.on('death', function(worker) { console.log('worker ' + worker.pid + ' died'); });} else { // Each worker processes have a http server. http.Server(function(req, res) { res.writeHead(200); res.end(host + ":" + port); }).listen(port, host); console.log("listening on.. " + host + ":" + port);}

Things to note:1. Node.js started to support Windows servers

• Supposedly runs faster on Windows J

1. If you are using cluster or need node 0.6 or greater, use node06 runtime

i.e. vmc push myapp --runtime=node06

2. This example spawns 4 node processes per instance!

• Watch out, it might exceeds default 64MB memory.

3. You may have to implement Redis based-session store

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Agenda – part 3

1. About Node.js• Internal working of Node.js• Buzz around Node.js• Who is using it• What kind of apps are being built

2. Coding in Node.js• Sync v/s Async coding (Callbacks)• Classes & Modules (CommonJS)• Node.js EventEmitters• npm & package.json

3. Node.js & Cloud Foundry (w/ demo)• Cloud Foundry – Open PaaS• Hello World app in Cloud Foundry• Scaling - Using Sticky Sessions• CloudFoundry Module & connecting to Redis, MongoDB etc • Express.js (RESTful) app• Socket.io + Express.js (Real-time) app

4. Demo• An sample app that uses concepts & modules talked above

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Cloud Foundry Resources

58

Primary Site : cloudfoundry.com

Open Source Site : cloudfoundry.org

Twitter : @cloudfoundry , hash tag #cfoundry

Blog : blog.cloudfoundry.com

FB : facebook.com/cloudfoundry

Support : support.cloudfoundry.com• Documentation

• Knowledge Base

• Q & A / Forums

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Questions

59

?Wednesday, March 28, 12

Thank You!@CloudFoundry

@chanezon

Website : www.cloudfoundry.comBlog : blog.cloudfoundry.comForum : support.cloudfoundry.com

t

t

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Books / Articles

§ Nick Carr, The Big Switch

§ Eric Raymond, The Art of Unix Programming

§ Weinberg, Psychology of Computer Programming

§ Wes python book

§ Mark html5 book

§ Kent Beck XP

§ Hunt, Thomas, The Pragmatic Programmer

§ Ade Oshineye, Apprenticeship Patterns

§ Matt Cutt's Ignite Talk IO 2011, Trying different things

§ Josh Bloch talk about api design

§ Larry and Sergey, Anatomy of a Search Engine

§ Rob Pike, The Practice of Programming

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Papers / Talks

§ Simon Wardley, Oscon 09 “Cloud - Why IT Matters”

§ Tim O’Reilly article on internet os

§ Peter Deutsch’s 8 Fallacies of Distributed Computing

§ Brewer’s CAP Theorem

§ Gregor Hohpe’s Starbucks Does Not Use Two-Phase Commit

§ Herb Sutter, Welcome to the Junglehttp://herbsutter.com/welcome-to-the-jungle/

§ Stuff I tag http://www.delicious.com/chanezon/

§ More specifically http://www.delicious.com/chanezon/cloudfoundry

§ My previous Talks http://www.slideshare.net/chanezon

§ My list of favorite books http://www.chanezon.com/pat/soft_books.html

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Acknowledgement

§ Drawings from my daughters Eliette

§ Slides from Dave McCrory, Derek Collison, Russell Acton, Alexandre Vasseur, Raja Rao

§ Chinese poetry from Wang Wei, Zhu Yunming, Jiao Dao, Li Bai from “The Anchor book of Chinese Poetry”, Tony Barnstone and Chou Ping

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