what's so special about node.js

What's so special about Node.js?

giancarlo.valente@gmail.comtwitter @gncvalente

years of front-end programming evolution

now on server-side

javascript

Fundamental videography

Ryan Dahl at JS.Conf 2009 show his creature

http://jsconf.eu/2009/video_nodejs_by_ryan_dahl.htmland also this ... http://vimeo.com/9968301

Fundamental videography

Douglas Crockford: “Crockford on JavaScript

Scene 6: Loopage” August 2010

http://www.yuiblog.com/blog/2010/08/30/yui-theater-douglas-crockford-crockford-on-javascript

-scene-6-loopage-52-min

node.js is special

What does

node.js, nginx, memcached

have in common ?

a C librarycalledlibevent

Apache vs Nginx

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

Apache vs Nginx

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

apache uses threads

nginx uses an event loop

... it's a different approachon building servers ...

with differnt strenghts / weaknesses

event loop approach scales better when has to serve

many clients with requests that doesn't need

so much "data crunching" elaboartion, but a lot of I/O

Ryan's idea! node.js is a thin layer

that glue 3 libraries togheter:

V8 js engine +

libev (event loop) +

libeio (async I/O)

blocking I/O

historically all programming languageshave blocking I/O

but, a problem arise:the very expensive "data processing machine" is not used in a very efficient

way

multi user systems

use of timesharing, in order to make the same computer

multiuser

in our modern"server side" code,

the same thing appens

how do we solve this?simple, we do the same thing.

We invented the Threads!

but now the situation is like this

Help !!! web real-time, long running sockets ... I've sent the newsletter with 90% discount !!! traffic jam !

has a different approach

event loop approach

event loop is used from many years in:

gamesgraphical UIs

...servers

single thread server

c1, c2, c3, c4 ---> S ---> I/O

multi-thread server

c1 ---> T1 ---> I/Oc2 ---> T2 ---> I/Oc3 ---> T3 ---> I/Oc4 ---> T4 ---> I/O

thread pool server

c9, c5, c1 ---> T1 ---> I/Oc10, c6, c2 ---> T2 ---> I/Oc11, c7, c3 ---> T3 ---> I/Oc12, c8, c4 ---> T4 ---> I/O

event loop

c1 ---> ST --> async I/Oc2 ---> c3 ---> c4 ---> c5 ---> c6 ---> c7 ---> c8 ---> c9 ---> c10 ---> c11 ---> c12 --->

so what's the point ...

also the browseris

mono-threadand works with an

event loop

when we writesetTimeout('timeout_trigger()', 2000)

we're not creating a new thread!

(as sometimes I've heard ...)

but we're subscribing a new event,

which will run our callback,

2 seconds from now

so ... why all this hype ?

who are the most expert professionals

in event driven programming

with non blocking I/O ?

the one that do this from years!

front-end developers!

accidental evolutionof a language

(video)http://www.yuiblog.com/blog/2010/08/30/

yui-theater-douglas-crockford-crockford-on-javascript-scene-6-loopage-52-min

part 2

Do we all jump on the node.js train?

maybe sometimes

but it's important to understand what are the

strenght of node

so we can know how and when to use it.

alternatives ?

yes,

but we can talk about themnext time ... :)

weaknesses

monothread (?)(also principal strength point)

.. you've to follow the rules

non blocking operations,develop in evented style