Writing robust Node.js applications

Node.js TutorialTom Hughes-Croucher, PrincipalJetpacks For Dinosaurs, LLCtom@jetpacksfordinosaurs.com@sh1mmer

Introduction• Tom Hughes-Croucher• Principal at Jetpacks for Dinosaurs• Node.js and High-performance web site consulting and training• Walmart, MySpace, Joyent,Yahoo!, NASA, Tesco, etc• Node.js contributor• Lead author of "Node: Up and Running"

Scalable Server-Side Code with JavaScript Node Up and Running Tom Hughes-Croucher http://ofps.oreilly.com/titles/9781449398583/http://shop.oreilly.com/product/0636920015956.do

Training Online In person

Node refresher

Interactive Debugging

Enki:~/Code/node-examples $ node --debughelloworld.jsdebugger listening on port 5858Server running at http://127.0.0.1:8124/

enki:~ sh1mmer$ ps -A | grep node19093 ttys001 0:00.39 node index.js19273 ttys002 0:00.00 grep nodeenki:~ sh1mmer$ kill -s USR1 19093

enki:~ sh1mmer$ node index.jsHit SIGUSR1 - starting debugger agent.debugger listening on port 5858

Enki:~ $ sudo npm install -g node-inspectornode-inspector@0.1.8 ./node_modules/node-inspector├── websocket-server@1.4.04└── paperboy@0.0.2Enki:~ $ node-inspectorvisit http://0.0.0.0:8080/debug?port=5858 to startdebugging

Exercises• Modify a basic HTTP server to return the text "Im learning Node"• Change the HTTP response to HTML and return your text in an HTML page• Return the User-Agent string from the browser as part of your HTML page

Express.js

Sinatra Style MVC framework

var app = require(express).createServer();app.get(/, function(req, res){ res.send(hello world);});app.listen(3000);

HTTP Verb Oriented

Middleware

app.use(express.bodyParser());app.use(express.cookieParser());app.post(/, function(req, res){ // Perhaps we posted several items with a form // (use the bodyParser() middleware for this) var items = req.body.items; console.log(items); res.send(logging);});

Templating

Exercise• Create an Express server• Make routes for ‘/’ & ‘/products’• Serve two different pages based on value of the query string parameter "page"• Create a redirect from /old to /new• Set a cookie on the client

Building a chat server

Node Architectures

The obviousarchitecture

Client Front-end DatabaseUser Node DB

What about this?

Heavy Front-endClient Processor Database Farm WorkUser Node Node Node Node DB Node Node Node Node

Don’t we want to move “heavy work”?

Client → Server Server → DB Computation Computation

Better architecture

Front-endClient Database Farm DBUser Node Node Node Node Big Slow Logging farm Disk Node Node Disk

Move work which isn’tuser-facing out of main event loop

Ensure consistency of Node processes

Distributing work

Cluster

Use load balancers to distribute across servers

node-proxy squid varnish haproxy

Unbundle SSL stud, stunnel, etchttp://vincent.bernat.im/en/blog/2011- ssl-benchmark.html#conclusion

Sharding

Disclaimer: Sharding is hardSee CAP theorem

Socket.io

Web Socket library

client and serverwith the shared API

<!DOCTYPE html><html><body><script src="/socket.io/socket.io.js"></script><script>var socket = io.connect(http://localhost);socket.connect();socket.on(connect, function(){ console.log(connect) })socket.on(message, function(){ console.log(message) })socket.on(disconnect, function(){ console.log(disconnect); })</script></body></html>

Transports• WebSocket• Adobe® Flash® Socket• AJAX long polling• AJAX multipart streaming• Forever iframe• JSONP Polling

options = { transports: [websocket], log: util.log }io.listen(server, options)

// note, io.listen() will create a http server for youvar io = require(socket.io).listen(80);io.sockets.on(connection, function (socket) { io.sockets.emit(this, { will: be received by everyone}); socket.on(private message, function (from, msg) { console.log(I received a private message by , from, saying ,msg); }); socket.on(disconnect, function () { sockets.emit(user disconnected); });});

Exercises• Create a socket.io connect to an express server• Create a route which loads a page that includes socket.io• Send "hello world" to the client sockets• Make the client respond with "thanks" and disconnect from the server

Using Redis with Socket.io

Why use Redis?• No shared memory• Cluster on server won’t share client data• Multiple servers can use the same Redis

Node in production

Error handling

var http = require(http);var req = http.request({ host: www.google.com, path: /, port: 80, method: POST }, function (response) { // Do stuff with the response here});

node.js:134 throw e; // process.nextTick error, or error event on ﬁrst tick^ Error: Uncaught, unspeciﬁed error event.at EventEmitter.emit (events.js:47:15) at Object.<anonymous> (/Users/you/y-u-no-listen-for-errors.js:5:9) at Module._compile(module.js:404:26) at Object..js (module.js:410:10) at Module.load(module.js:336:31) at Function._load (module.js:297:12) atArray.<anonymous> (module.js:423:10) at EventEmitter._tickCallback(node.js:126:26)

var http = require(http);try { var req = http.request({ host: www.google.com, path: /, port: 80, method: POST }, function (response) { // Do stuff with the response here });} catch(e) {

// Suppress errorsprocess.on(uncaughtException, function (err) { // Log it! console.dir(err);});

EventEmitter leaks

(node) warning: possible EventEmitter memory leak detected. 11listeners added. Use emitter.setMaxListeners() to increase limit. Trace: at Pool.<anonymous> (events.js:101:17) at Object.proxyRequest (~/http-proxy/lib/node-http-proxy.js:185:7) at Server.<anonymous> (/Users/some-user/myapp.js:14:9) at Server.emit (events.js:45:17) at HTTPParser.onIncoming (http.js:1078:12) at HTTPParser.onHeadersComplete (http.js:87:31) at Socket.ondata (http.js:977:22) at Socket._onReadable (net.js:654:27) at IOWatcher.onReadable [as callback] (net.js:156:10)

once() is awesome

Process monitoring

Upstart

description "node.js server"author "croucher`"start on startupstop on shutdownscript # We found $HOME is needed. Without it, we ran intoproblems export HOME="/root" exec /usr/local/bin/node /var/noderoot/index.js 2>&1 >> /var/log/node.logend script

forever

$ cd /path/to/your/app$ forever start bin/yourappinfo: Running action: startinfo: Forever processingﬁle: examples/server.js$ forever listinfo: Running action: listinfo: Forever processes running [0] bin/yourapp [77041, 77040] /Users/You/.forever20dL.log 0:0:0:1.788

NPM Packaging

Enki:~/Code/node-dnsserve(master) $ lsLICENSE README dnsserver.jspackage.jsonEnki:~/Code/node-dnsserve(master) $

{ "name": "dns-server", "description": "DNS server for Node", "version": "0.0.1a", "author": "Tom Hughes-Croucher<tom.croucher@gmail.com>", "main" : "dnsserver"}

Enki:~/Code/node-dnsserve(master) $ sudo npminstall . -gdns-server@0.0.1a /usr/local/lib/node_modules/dns-serverEnki:~/Code/node-dnsserve(master) $

Enki:~/Code/node-dnsserve(master) $ sudo npm link/usr/local/lib/node_modules/dns-server -> /Users/sh1mmer/Code/node-dnsserveEnki:~/Code/node-dnsserve(master) $ npm ls -g/usr/local/lib├── dns-server@0.0.1a -> /Users/sh1mmer/Code/node-dnsserve└─┬ npm@1.0.6 ├── abbrev@1.0.3 ├── node-uuid@1.1.0 ├── nopt@1.0.4 └── semver@1.0.5Enki:~/Code/node-dnsserve(master) $

Enki:~/Code/node-dnsserve(master) $ npm adduserUsername: foobarbazPassword:Email:

Enki:~/Code/node-dnsserve(master) $ npm publishnpm WARN Sending authorization over insecurechannel.Enki:~/Code/node-dnsserve(master) $

{ "name": "winston", "description": "A multi-transport async logging library for Node.js", "version": "0.2.7", "author": "Charlie Robbins <charlie.robbins@gmail.com>", "contributors": [ { "name": "Matthew Bergman", "email": "mzbphoto@gmail.com" } ], "repository": { "type": "git", "url": "http://github.com/indexzero/winston.git" }, "keywords": ["logging", "sysadmin", "tools"], "dependencies": { "colors": ">= 0.3.0", "eyes": ">= 0.1.6", "loggly": ">= 0.1.4", "vows": ">= 0.5.2" }, "main": "./lib/winston", "scripts": { "test": "vows test/*-test.js --spec" }, "engines": { "node": ">= 0.3.0" }}

{ "name": "winston", "description": "A multi-transport async logging library for Node.js", "version": "0.2.7", "author": "Charlie Robbins <charlie.robbins@gmail.com>", "contributors": [ { "name": "Matthew Bergman", "email": "mzbphoto@gmail.com" } ], "repository": { "type": "git", "url": "http://github.com/indexzero/winston.git" }, "keywords": ["logging", "sysadmin", "tools"], "dependencies": { "colors": ">= 0.x.x", "eyes": ">= 0.1.x", "loggly": ">= 0.1.x", "vows": ">= 0.5.x" }, "main": "./lib/winston", "scripts": { "test": "vows test/*-test.js --spec" }, "engines": { "node": ">= 0.3.0" }}

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Writing robust Node.js applications

by Tom Hughes-Croucher

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