Save 10% off ANY FITC event with discount code 'slideshare' See our upcoming events at www.fitc.ca Node.js: The What, The How and The When with Richard Nieuwenhuis

1. Node.js
Awesome, Lightweight, JavaScript, High Performance
qr.net/fitc2014

2. WHO AM I?
•
Richard Nieuwenhuis
•
32 years old
•
MediaMonks
•
7 years a Monk
•
Lead of Operations / Head of
development

4. Overview
•
What is Node.js
•
Some small examples
•
Asynchrony here, asynchrony there
•
Some (popular) Node.js modules
•
Socket.io
•
High performance examples
•
Some tips & tricks

5. When and by whom?
•
First made public in 2009
•
Ryan Lienhart Dahl
•
Currently at version 0.10.25*
•
“Why is a progress bar so difficult?”
•
•
“Why the heck are we polling???”
This sheet was created 17-2-2014

6. What nodejs.org says
•
“Node.js is a platform built on Chrome's JavaScript runtime for
easily building fast, scalable network applications. Node.js uses
an event-driven, non-blocking I/O model that makes it lightweight
and efficient, perfect for data-intensive real-time applications that
run across distributed devices.”

7. In short how many people see it
•
Server side JavaScript!

8. High Level Component overview
Node.js
V8
Event Loop
(Libuv)

9. Where to begin?
•
Download & Install Node.js
•
•
Use your favorite IDE
Node.js API/Modules:
•
•
Sort of API‟s which expose Node functions
•
Allows the Node.js community to extend Node.js
•
•
Built-in
Super lightweight
Add-ons
•
Quite a big community
•
The NPM (Node Package Manager)

10. Some Node.js APIs/Modules
•
http
•
•
Provides basic functions for creating a server and handling requests
https
•
•
For setting up a secured server
assert
•
•
For creating unit tests for your code (NodeTDD!)
fs
•
For doing stuff with the File System

11. Some Node.js
APIs/Modules continued
•
querystring
•
•
For parsing the query string of a request
url
•
•
functions for parsing and resolving URL‟s
repl: Read-Eval-Print-Loop
•
Good for debugging and testing

12. Let‟s build something simple
•
Simple server
•
Every “Hello World” Example starts with this.
•
Read the files of a folder.
•
Print the file names in the browser in sorted fashion.
•
PS. Examples show Node specifics and are to illustrate points and are by no
means “elegant, save” etc :-)

13. Create our own module: sorterservice.js
function sortFileNames(fileNames){
return fileNames.sort();
}
exports.sortFileNames = sortFileNames;
-
a module can be a single file
a module can be a folder
exports is a special object to define properties
-
Can be any type: function, strings, etc

14. Requiring needed modules
//require the needed modules
var http = require('http');
var fs
= require('fs');
var sorter = require('./sorterservice');

15. Create server and verify requests
http.createServer(function(req, res){
switch(req.method){
case 'POST':
console.log('This is a post request');
break;
case 'GET':
switch(req.url){
case '/':
readFileNames(res);
break;
case '/showfiles„:
readFileNames(res);
break;
case '/favicon.ico„:
break;
}
break;
default:
res.setHeader('Content-Type', 'text/plain');
res.end("This method I simply do not know");
}

16. Let‟s read the file names
function readFileNames(res){
var dirName = './files';
var html = '';
var fileNames
= fs.readdirSync(dirName);
var sortedFileNames = sorter.sortFileNames(fileNames);
html += '<ol>';
for(var index in sortedFileNames){
html += '<li>' + sortedFileNames[index] + '</li>';
}
html += '</ol>';
sendFileNames(res, html);
}

17. One last thing & Does it work?
function sendFileNames(res, html){
res.setHeader('Content-Type', 'text/html');
res.end(html);
}

18. Two big things not OK here
Which are also two important Node aspects
1)
Error handling
2)
A-synchronous architecture

19. Main problem 1
function readFileNames(res){
var dirName = './files';
var html = '';
var fileNames = [];
fileNames
= fs.readdirSync(dirName);
var sortedFileNames = sorter.sortFileNames(fileNames);
html += '<ol>';
for(var index in sortedFileNames){
html += '<li>' + sortedFileNames[index] + '</li>';
}
html += '</ol>';
sendFileNames(res, html);
}

20. What did we see?
•
The server crashed and Node stopped running
•
A lot less forgiving than PHP for example
•
Not OK during a super bowl commercial where millions of Dollars are spend
;-)
Tip: Look at the Node.js module forever

21. In this case a simple
if (fs.existsSync(dirName)){
fileNames = fs.readdirSync(dirName);
}
Would suffice….
•
Defensive programming is super important in Node
•
Verify everything!
•
Valid user input
•
Expect the unexpected (even if you expect otherwise)
•
Act on any error that may occur (and log it)
•
Have a process in place to restart node just to be sure (forever module)

22. “Problemo” numero dos
fs.readdirSync(dirName);
Node is a single threaded running process.

23. Synchronous development
•
Blocking/Synchronous requests are bad
•
•
It will “block” the continuation of your logic for the amount of time the
blocking request is active (requesting a JSON file for example)
On the server you basically have the same problems
•
•
But it will affect all visitors immediately when one request is stalling
Can ultimately lead to a crashing server

24. Synchronous development
http.createServer(function(req, res){
switch(req.method){
case 'POST':
console.log('This is a post request');
break;
case 'GET':
//”Select *” all 200K users from the database
//Give it back to the response
}
}).listen(8888);

25. Continued
Pffff, I need to
return 200K
rows?
Request
Cpu to r2: Sorry, I
am doing nothing,
but the DB is
sooooo slowww
Request 2
Going to take
me a while!
doQuery()
CPU
processData()
Cpu
time
DB

26. The Event Loop
Take this event
loop!:
doQuery(cb)
Pffff, I need to
return 200K
rows?
Going to take me
a while!
Request
CPU to r2: thanks
man! I am
processing your
request
Request 2
CPU
processData()
E
loop
callback
DB

27. A-Synchronous Node development
A lot of Node functions have a-synchronous versions.
fs.readdir(dirName, function(err, data){
if (err){
console.log();
}
var sortedFileNames = sorter.sortFileNames(data);
//The other code
--------------------------http.createServer(function(req, res){……

28. A-Synchronous Node development
•
A-synchronize as much as possible to keep the main process as “free” as
possible.
•
•
Much more necessary when it is a high-performance environment
It is not the holy grail! Keep the Big O in mind: for (var x = 0; x < 25.5Billion;
x++)
•
Sequencing & parallel
•
Can become quite messy and unreadable

29. A highly unlikely hypothetical situation
•
Read the files from Dir A
•
Merge the content of all files of Dir A into one file
•
Read the files from Dir B
•
Append the content of step 1 to all files in Dir B
•
Store these results in the Database

30. Would look something like this
aSynReadDir('A/', function(files) {
mergeFiles(files, function(fileContents) {
aSynReadDir('B/', function(files) {
appendFiles(fileContents, files, function(appendedFiles) {
insertIntoDatabase(appendedFiles, function() {
});
});
});
});
});

31. Useful Node Modules: Socket.io
•
Latest browsers support Web sockets
•
IE10+
•
Chrome
•
FireFox
•
“Weirdly” on Android only starting from 4.4…
•
Socket.io leverages the Web socket technology for bi-directional
communication between clients & servers:
•
With degradability in place for the “older” browsers!

32. Socket.io continued
•
Very nice for real time applications with a lot of concurrent users.
•
Browser based games where you mobile is the controller
•
Second screen applications
•
Updating the client:
•
Chat
•
Real time statistics
•
News updates
•
Etc

33. Small example (Server)
var server = http.createServer(function(req, res){
//code here
});
var io = socketio.listen(server);
function sendRandomMessage(){
var index = Math.floor((Math.random()*4));
io.sockets.send(words[index]);
}

34. Small example (Client)
var socket = io.connect();
socket.on('message', function (message) {
console.log(„I received the message ' + message);
var m = document.createElement('p');
m.innerText = message;
document.getElementById('text').appendChild(m);
});

35. Event Listener
socket.on('message', function (message)……
socket.emit(„fired‟, {message: yep, you are fired});

36. Other Useful Node Modules
"dependencies": {
"express": "3.4.7", // Web Framework
"express-validator": "1.0.1",
"request": "2.25.0", //
"redis": "0.10.0", //Redis: High performance in memory DB
"hiredis": "0.1.16", // To make Redis even faster with C written stuff
"redis-sentinel": "0.0.5", // Redis failover
"http-auth": "*", //for authentication
"openid": "0.5.5", //Open ID client
"statsd-client": "*", //NodeJS deamon for logging request s
tatistics
"facebook-node-sdk": "0.2.0",
"librato-metrics": "0.0.7",
"statsd-client": "0.0.15"
}

37. ADIDAS
NITROCHARGE
An interactive cinematic
experience using your mobile
phone as a controller.
Produced for DDB & Tribal
Case
Video

38. KLM
CLAIM YOUR
PLACE IN SPACE
Are you ready to win the ultimate journey
of inspiration? Claim your spot in space
Produced for DDB & Tribal Amsterdam
Case
Video

39. THE VOICE
OF HOLLAND
Talpa
This season you can be a
coach at home. Show your
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Voice of Holland Thuiscoach
app.
Case
Video

40. THANK YOU!
•
We are looking for new awesome
developers!
•
Questions: richard@mediamonks.com