NodeJSall Levels

I N T R O T O N O D E . J S- L E V E L O N E -

INTRO TO NODE.JS

WHAT IS NODE.JS?

It’s fast because it’s mostly C code

Allows you to build scalable network applications using JavaScript on the server-side.

V8 JavaScript Runtime

Node.js

INTRO TO NODE.JS

WHAT COULD YOU BUILD?• Websocket Server• Fast File Upload Client• Ad Server• Any Real-Time Data Apps

Like a chat server

INTRO TO NODE.JS

WHAT IS NODE.JS NOT ?• A Web Framework• For Beginners It’s very low level• Multi-threaded

You can think of it as a single threaded server

INTRO TO NODE.JS

OBJECTIVE: PRINT FILE CONTENTS

This is a “Callback”

Read file from Filesystem, set equal to “contents”Print contents

• Blocking Code

• Non-Blocking Code

Do something else

Read file from Filesystemwhenever you’re complete, print the contents

Do Something else

console.log(contents);

INTRO TO NODE.JS

BLOCKING VS NON-BLOCKING

var contents = fs.readFileSync('/etc/hosts');console.log(contents);

console.log('Doing something else');

• Blocking Code

• Non-Blocking Code

console.log('Doing something else');Stop process until

complete

fs.readFile('/etc/hosts', function(err, contents) {

});

fs.readFile('/etc/hosts', function(err, contents) {console.log(contents);

});

INTRO TO NODE.JS

CALLBACK ALTERNATE SYNTAX

var callback = function(err, contents) { console.log(contents);}

fs.readFile('/etc/hosts', callback);

Same as

INTRO TO NODE.JS

BLOCKING VS NON-BLOCKING

blocking

0snon-blocking

10s5s

0s 10s5s

fs.readFile('/etc/hosts', callback);fs.readFile('/etc/inetcfg', callback);

var callback = function(err, contents) { console.log(contents);}

hello.js

NODE.JS HELLO DOG

$ curl http://localhost:8080

Hello, this is dog.

How we require modules

Status code in headerResponse body

Close the connectionListen for connections on this port

$ node hello.js Run the server

var http = require('http');

http.createServer(function(request, response) {response.writeHead(200);response.write("Hello, this is dog.");response.end();

}).listen(8080, function(){console.log('Listening on port 8080...');

Listening on port 8080...

});

THE EVENT LOOPvar http = require('http');http.createServer(function(request, response) {

}).listen(8080, function(){ console.log('Listening on port 8080...');

Starts the Event Loop when finished

...

Known Eventsrequest

Checking for

Events

Run the Callback});

INTRO TO NODE.JS

WHY JAVASCRIPT ?“JavaScript has certain characteristics that make it very different than other dynamic languages, namely that it has no concept of threads. Its model of concurrency is completely based around events.”

- Ryan Dahl

THE EVENT LOOPKnown Events

requestChecking for

Eventsconnection

close

Event Queue

closerequest

Events processed one at a time

INTRO TO NODE.JS

WITH LONG RUNNING PROCESS

Represent long running process


http.createServer(function(request, response) {

}).listen(8080);

response.writeHead(200);

response.write("Dog is done.");response.end();

setTimeout(function(){

}, 5000); 5000ms = 5 seconds

response.write("Dog is running.");

INTRO TO NODE.JS

TWO CALLBACKS HEREvar http = require('http');

http.createServer(function(request, response) {response.writeHead(200);

request

timeout

}).listen(8080);

response.write("Dog is done.");response.end();


}, 5000);

response.write("Dog is running.");

TWO CALLBACKS TIMELINE

0s 10s5s

Request comes in, triggers request event

Request Callback executessetTimeout registered

Request comes in, triggers request event

Request Callback executessetTimeout registered

triggers setTimeout eventsetTimeout Callback executes

triggers setTimeout eventsetTimeout Callback

request

timeout

WITH BLOCKING TIMELINE

0s 10s5s

Request comes in, triggers request event Request Callback executes

setTimeout executed

Request comes in, waits for server

Request comes in

triggers setTimeout eventsetTimeout Callback executedWasted Time

Request Callback executes

INTRO TO NODE.JS

• Calls out to web services

TYPICAL BLOCKING THINGS

• Reads/Writes on the Database• Calls to extensions

E V E N T S- L E V E L T W O -

E V E N T S

EVENTS IN THE DOM

The DOM

The DOM triggers Events

click

events

you can listen for those events

submit

hover

When ‘click’ event is triggered!

attach

$("p").on("click", function(){ ... });

E V E N T S

EVENTS IN NODE

EventEmitter

Many objects in Node emit events

net.Serverrequestevent

EventEmitterfs.readStream

dataevent

E V E N T S

CUSTOM EVENT EMITTERS

var logger = new EventEmitter();

logger.emit('error', 'Spilled Milk');

ERR: Spilled Milk

logger.emit('error', 'Eggs Cracked');

var EventEmitter = require('events').EventEmitter;

error warn info

listen for error eventlogger.on('error', function(message){

console.log('ERR: ' + message);});

ERR: Eggs Cracked

events

E V E N T S

EVENTS IN NODE

EventEmitter

Many objects in Node emit eventsnet.Server

requestevent

When ‘request’ event is emitted!function(request, response){ .. }

emit

attach

E V E N T S

HTTP ECHO SERVER!http.createServer(function(request, response){ ... });

But what is really going on here?http://nodejs.org/api/

http://nodejs.org/api/

E V E N T S

BREAKING IT DOWN!http.createServer(function(request, response){ ... });

!http.createServer(function(request, response){ ... });

E V E N T S

ALTERNATE SYNTAX

!var server = http.createServer();function(request, response){ ... });server.on('request',

This is how we

Same as

function(){ ... });server.on('close',

add event listeners

S T R E A M S- L E V E L T H R E E -

S T R E A M S

WHAT ARE STREAMS?

Start ProcessingImmediately

Streams can be readable, writeable, or both

The API described here is for streams in Node version v0.10.x a.k.a. streams2

S T R E A M S

STREAMING RESPONSE

Our browser receives "Dog is running."

"Dog is done."

(5 seconds later)


}).listen(8080);


response.write("<p>Dog is done.</p>");response.end();


}, 5000);

response.write("<p>Dog is running.</p>");

readable stream writable stream

var chunk = null;while (null !== (chunk = request.read())) {!}

HOW TO READ FROM THE REQUEST ?


request.on('readable', function() {

});

response.end();

}).listen(8080)

request.on('end', function() {

});


(chunk.toString());console.log

EventEmitterReadable Stream readable

eventsemit

end

Let’s print what we receive from the request.

HOW TO READ FROM THE REQUEST ?http.createServer(function(request, response) {


});

response.end();

}).listen(8080)

request.on('end', function() {

});


response.write(chunk); request.pipe(response);

var chunk = null;while (null !== (chunk = request.read())) {!}

S T R E A M S

LET’S CREATE AN ECHO SERVER!http.createServer(function(request, response) {

}).listen(8080)request.pipe(response);response.writeHead(200);

$ curl -d 'hello' http://localhost:8080

Hello on client

cat 'bleh.txt' | grep 'something'Kinda like on the command line

http://localhost:8080

S T R E A M S

DOCUMENTATION http://nodejs.org/api/

Stability Scores

http://nodejs.org/api/

S T R E A M S

READING AND WRITING A FILEvar fs = require('fs');

var file = fs.createReadStream("readme.md");var newFile = fs.createWriteStream("readme_copy.md");

require filesystem module

file.pipe(newFile);

http://gulpjs.com/Build system built on top of Streams

S T R E A M S

UPLOAD A FILE



request.pipe(newFile);

}).listen(8080);

response.end('uploaded!');request.on('end', function() {

});

var fs = require('fs');

var newFile = fs.createWriteStream("readme_copy.md");

$ curl --upload-file readme.md http://localhost:8080

uploaded!


THE AWESOME STREAMING

client storage

server

original filetransferred file

non-blocking

0s 10s5s

S T R E A M S

FILE UPLOADING PROGRESS

S T R E A M S

FILE UPLOADING PROGRESS$ curl --upload-file file.jpg http://localhost:8080

progress: 3%progress: 6%progress: 9%progress: 12%progress: 13%...progress: 99%progress: 100%

Outputs:

• HTTP Server • File SystemWe’re going to need:


S T R E A M S

REMEMBER THIS CODE?var fs = require('fs');





}).listen(8080);

response.end('uploaded!');request.on('end', function() {

});

S T R E A M S

REMEMBER THIS CODE?http.createServer(function(request, response) {

}).listen(8080);

...

uploadedBytes += chunk.length;var progress = (uploadedBytes / fileBytes) * 100;response.write("progress: " + parseInt(progress, 10) + "%\n");

var uploadedBytes = 0;var fileBytes = request.headers['content-length'];


});


while(null !== (chunk = request.read())){

}

var chunk = null;


S T R E A M S

SHOWING PROGRESS

M O D U L E S- L E V E L F O U R -

M O D U L E S

REQUIRING MODULEShttp.js

How does it find these files?


var fs = require('fs'); fs.js

How does ‘require’ return the libraries?

M O D U L E S

LET’S CREATE OUR OWN MODULE

custom_hello.js

custom_goodbye.js

app.js

module.exports = hello;

var hello = require('./custom_hello');

hello();

exports defines what require returns

var hello = function() { console.log("hello!");}

exports.goodbye = function() { console.log("bye!");}

var gb = require('./custom_goodbye');

gb.goodbye();

require('./custom_goodbye').goodbye(); If we only need to call once

M O D U L E S

EXPORT MULTIPLE FUNCTIONS

my_module.js

app.js

var foo = function() { ... }var bar = function() { ... }

exports.foo = fooexports.bar = bar

var myMod = require('./my_module');myMod.foo();myMod.bar();

my_module.js

foo

bar

var baz = function() { ... }baz

“private”

M O D U L E S

MAKING HTTP REQUESTSapp.js

logs response body

begins request


var options = { host: 'localhost', port: 8080, path: '/', method: 'POST' }

var request = http.request(options, function(response){response.on('data', function(data){console.log(data);

});});

request.end();request.write(message);

finishes request

var message = "Here's looking at you, kid.";

M O D U L E S

ENCAPSULATING THE FUNCTIONapp.jsvar http = require('http');

var makeRequest = function(message) { var options = { host: 'localhost', port: 8080, path: '/', method: 'POST' }

var request = http.request(options, function(response){response.on('data', function(data){console.log(data);

});});

request.end();}

makeRequest("Here's looking at you, kid.");

request.write(message);

Text

M O D U L E S

CREATING & USING A MODULEmake_request.jsvar http = require('http');

var makeRequest = function(message) {

}

module.exports = makeRequest;

...

app.jsvar makeRequest = require('./make_request');

makeRequest("Here's looking at you, kid");makeRequest("Hello, this is dog");

Where does require look for modules?

M O D U L E S

REQUIRE SEARCH

var make_request = require('make_request')

/Home/eric/my_app/app.js

• /Home/eric/my_app/node_modules/make_request.js

var make_request = require('./make_request')var make_request = require('../make_request')var make_request = require('/Users/eric/nodes/make_request')

• /Home/eric/node_modules/make_request.js• /Home/node_modules/make_request.js• /node_modules/make_request.js

look in same directorylook in parent directory

Search in node_modules directories

However, all packages are directories

M O D U L E S

NPM: THE USERLAND SEAPackage manager for node

• Comes with node• Module Repository• Dependency Management• Easily publish moduleshttp://npmjs.org

http://npmjs.org

M O D U L E S

INSTALLING A NPM MODULE

$ npm install request

In /Home/my_app

Home my_app reques node_modules

Installs into local node_modules directory

var request = require('request');

In /Home/my_app/app.js

Loads from local node_modules directory

M O D U L E S

LOCAL VS GLOBAL

Global npm modules can’t be required

$ npm install coffee-script -g

Install modules with executables globally

$ coffee app.coffee

var coffee = require('coffee-script');

$ npm install coffee-script

var coffee = require('coffee-script');

global

Install them locally

M O D U L E S

FINDING MODULESnpm registry

$ npm search request

npm command line

github search

M O D U L E S

DEFINING YOUR DEPENDENCIESmy_app/package.json

version number

$ npm install

my_app connect node_modules

Installs into the node_modules directory

{"name": "My App","version": "1",

"dependencies": { "connect": "1.8.7" }}

M O D U L E S

DEPENDENCIES

my_app connect node_modules

Installs sub-dependencies

connect node_modules qs

connect node_modules mime

connect node_modules formidable

"dependencies": { "connect": "1.8.7" }

my_app/package.json

M O D U L E S

SEMANTIC VERSIONING"connect": "1.8.7" 1 8 7

Major Minor Patch. .

http://semver.org/ "connect": "~1.8.7" >=1.8.7 <1.9.0 Considered safe

"connect": "~1.8" >=1.8.0 <1.9.0 API could change

"connect": "~1" >=1.0.0 <2.0.0 DangerousRanges

E X P R E S S- L E V E L F I V E -

E X P R E S S

EXPRESS“Sinatra inspired web development framework for Node.js -- insanely fast, flexible, and simple”

• Easy route URLs to callbacks • Middleware (from Connect) • Environment based configuration • Redirection helpers • File Uploads

E X P R E S S

$ npm install --save expressvar express = require('express');

var app = express();

app.get('/', function(request, response) { response.sendFile(__dirname + "/index.html");});

app.listen(8080);

$ curl http://localhost:8080/> 200 OK

root route

current directory

Installs the module and adds to package.json


E X P R E S S

INTRODUCING EXPRESS

E X P R E S S

EXPRESS ROUTESapp.js

route definition

get the last 10 tweets for screen_name

pipe the request to response

var request = require('request');var url = require('url');

app.get('/tweets/:username', function(req, response) {

var username = req.params.username;

options = { protocol: "http:", host: 'api.twitter.com', pathname: '/1/statuses/user_timeline.json', query: { screen_name: username, count: 10} }

var twitterUrl = url.format(options); request(twitterUrl).pipe(response);});

E X P R E S S

EXPRESS ROUTES

E X P R E S S

EXPRESS + HTML

E X P R E S S

EJS TEMPLATES

$ npm install --save ejs

/Home/eric/my_app/views

"dependencies": { "express": "4.9.6",

}

my_app/package.json

default directory

"ejs": "1.0.0" Installs the module and adds to package.json

E X P R E S S

EXPRESS TEMPLATESapp.js

views/tweets.ejs

app.get('/tweets/:username', function(req, response) {...request(url, function(err, res, body) {var tweets = JSON.parse(body);

response.render('tweets.ejs'); });});

<h1>Tweets for @<%= name %></h1><ul> <% tweets.forEach(function(tweet){ %> <li><%= tweet.text %></li> <% }); %></ul>

response.locals = {tweets: tweets, name: username};

E X P R E S S

EXPRESS TEMPLATES

E X P R E S S

TEMPLATE LAYOUTS

S O C K E T . I O- L E V E L S I X -

S O C K E T. I O

CHATTR

S O C K E T. I O

WEBSOCKETS

browser traditional serverTraditional request/response cycle

Using duplexed websocket connection

S O C K E T. I O

WEBSOCKETS

browser socket.io

SOCKET.IO FOR WEBSOCKETS

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

Abstracts websockets with fallbacks

io.on('connection', function(client) {

});console.log('Client connected...');

$ npm install --save socket.io

app.js

var io = require('socket.io')(server);

server.listen(8080);

app.get('/', function (req, res) { res.sendFile(__dirname + '/index.html');});

S O C K E T. I O

SOCKET.IO FOR WEBSOCKETSsocket.io client connects to the server

<script src="/socket.io/socket.io.js"></script>

var socket = io.connect('http://localhost:8080');<script>

</script>

index.html

S O C K E T. I O

S O C K E T. I O

SENDING MESSAGES TO CLIENTio.on('connection', function(client) {

});

console.log('Client connected...');

<script src="/socket.io/socket.io.js"></script>


</script>

app.js

index.html

client.emit('messages', { hello: 'world' });

socket.on('messages', function (data) {

});alert(data.hello);

emit the ‘messages’ event on the client

listen for ‘messages’ events

S O C K E T. I O

CHATTR HELLO WORLD

S O C K E T. I O

SENDING MESSAGES TO SERVERio.on('connection', function(client) {

});


</script>

app.js

index.html

client.on('messages', function (data) {

});console.log(data);

$('#chat_form').submit(function(e){var message = $('#chat_input').val();

socket.emit('messages', message);});

listen for ‘messages’ events

emit the ‘messages’ event on the server

S O C K E T. I O

CHATTR HELLO WORLD

S O C K E T. I O

BROADCASTING MESSAGES

clients

server

app.js!socket.broadcast.emit("message", 'Hello');

S O C K E T. I O

BROADCASTING MESSAGESio.on('connection', function(client) {

});

<script>

</script>

app.js

index.html

client.on('messages', function (data) {

});

...

broadcast message to all other clients connectedclient.broadcast.emit("messages", data);

socket.on('messages', function(data) { insertMessage(data) });insert message into the chat

S O C K E T. I O

BROADCASTING MESSAGES

S O C K E T. I O

SAVING DATA ON THE SOCKETio.on('connection', function(client) {

});

var server = io.connect('http://localhost:8080');<script>

</script>

app.js

index.html

client.on('join', function(name) {client.nickname = name;

});set the nickname associated

with this client

server.on('connect', function(data) {$('#status').html('Connected to chattr');nickname = prompt("What is your nickname?");

server.emit('join', nickname);});

notify the server of the users nickname

S O C K E T. I O

SAVING DATA ON THE CLIENTio.on('connection', function(client) {

});

app.jsclient.on('join', function(name) {

client.nickname = name;});

client.on('messages', function(data){

});

client.broadcast.emit("message", nickname + ": " + message);broadcast with the name and message

client.emit("messages", nickname + ": " + message);send the same message back to our client

set the nickname associated with this client

var nickname = client.nickname;get the nickname of this client before broadcasting message

P E R S I S T I N G D A T A- L E V E L S E V E N -

P E R S I S T I N G D A T A

RECENT MESSAGES

});});


RECENT MESSAGESio.sockets.on('connection', function(client) {client.on('join', function(name) {client.nickname = name;client.broadcast.emit("chat", name + " joined the chat");

});client.on("messages", function(message){client.broadcast.emit("messages", client.nickname + ": " + message);

app.js

client.emit("messages", client.nickname + ": " + message);

});});

STORING MESSAGES

io.sockets.on('connection', function(client) {client.on("messages", function(message){

app.js

storeMessage(client.nickname, message);

var messages = []; store messages in arrayvar storeMessage = function(name, data){

messages.push({name: name, data: data});if (messages.length > 10) {

messages.shift();}

}

add message to end of array

if more than 10 messages long, remove the first one

when client sends a message call storeMessage

client.broadcast.emit("messages", client.nickname + ": " + message);client.emit("messages", client.nickname + ": " + message);


EMITTING MESSAGESio.sockets.on('connection', function(client) {

});

app.js

client.on('join', function(name) {

});

messages.forEach(function(message) { client.emit("messages", message.name + ": " + message.data); }); iterate through messages array

and emit a message on the connecting client for each one

...


RECENT MESSAGES


PERSISTING STORES• MongoDB • CouchDB • PostgreSQL • Memcached • Riak

All non-blocking!

Redis is a key-value store


REDIS DATA STRUCTURES

Strings SET, GET, APPEND, DECR, INCR...

Hashes HSET, HGET, HDEL, HGETALL...

Lists LPUSH, LREM, LTRIM, RPOP, LINSERT...

Sets SADD, SREM, SMOVE, SMEMBERS...

Sorted Sets ZADD, ZREM, ZSCORE, ZRANK...

data structure commands


REDIS COMMAND DOCUMENTATION


NODE REDIS

client.get("message1", function(err, reply){ console.log(reply);});


REDIS

key value

"hello, yes this is dog"

var redis = require('redis');var client = redis.createClient();

client.set("message1", "hello, yes this is dog");client.set("message2", "hello, no this is spider");

commands are non-blocking

$ npm install redis --save


REDIS LISTS: PUSHINGAdd a string to the “messages” list

"1"

var message = "Hello, no this is spider";client.lpush("messages", message, function(err, reply){ console.log(reply);}); "2"

replies with list length

Add another string to “messages”

var message = "Hello, this is dog";client.lpush("messages", message, function(err, reply){

console.log(reply);});


REDIS LISTS: RETRIEVINGUsing LPUSH & LTRIM

trim keeps first two strings and removes the rest

Retrieving from list client.lrange("messages", 0, -1, function(err, messages){

console.log(messages);})

["Hello, no this is spider", "Oh sorry, wrong number"]

replies with all strings in list

client.ltrim("messages", 0, 1);

var message = "Hello, this is dog";client.lpush("messages", message, function(err, reply){

});


CONVERTING MESSAGES TO REDIS

var storeMessage = function(name, data){messages.push({name: name, data: data});

if (messages.length > 10) { messages.shift(); }}

Let’s use the List data-structure

app.js


CONVERTING STOREMESSAGE

var storeMessage = function(name, data){

}

var redisClient = redis.createClient();

var message = JSON.stringify({name: name, data: data});

redisClient.lpush("messages", message, function(err, response) {redisClient.ltrim("messages", 0, 9);

});keeps newest 10 items

app.js

need to turn object into string to store in redis


OUTPUT FROM LISTclient.on('join', function(name) {

});

messages.forEach(function(message) {client.emit("messages", message.name + ": " + message.data);

});

app.js


OUTPUT FROM LIST

client.on('join', function(name) {

});

messages.forEach(function(message) {

client.emit("messages", message.name + ": " + message.data);

});

redisClient.lrange("messages", 0, -1, function(err, messages){messages = messages.reverse();

message = JSON.parse(message);

});

app.js

reverse so they are emitted in correct order

parse into JSON object


IN ACTION


CURRENT CHATTER LISTSets are lists of unique data

client.sadd("names", "Dog");client.sadd("names", "Spider");client.sadd("names", "Gregg");

client.srem("names", "Spider");

!client.smembers("names", function(err, names){ console.log(names);});

["Dog", "Gregg"]

reply with all members of set

add & remove members of the names set

app.js


ADDING CHATTERSclient.on('join', function(name){

client.broadcast.emit("add chatter", name); redisClient.sadd("chatters", name);});

notify other clients a chatter has joined

add name to chatters set

index.htmlsocket.on('add chatter', function(name) {

var chatter = $('<li>'+name+'</li>').data('name', name); $('#chatters').append(chatter);});


ADDING CHATTERS (CONT)client.on('join', function(name){client.broadcast.emit("add chatter", name);

redisClient.sadd("chatters", name);});

app.js

emit all the currently logged in chatters to the newly connected client

redisClient.smembers('names', function(err, names) { names.forEach(function(name){ client.emit('add chatter', name); });});


REMOVING CHATTERSclient.on('disconnect', function(name){ app.js

index.html

client.broadcast.emit("remove chatter", client.nickname); redisClient.srem("chatters", client.nickname;);});

remove chatter when they disconnect from server

server.on('remove chatter', function(name) { $('#chatters li[data-name=’+ name + ']').remove();});


WELCOME TO CHATTR

Documents

NodeJSall Levels