rest in ( a mobile ) peace @ whymca 05-21-2011

RESTin (a mobile) peace

Alessandro Nadalin

May, 21st 2011

AgendaRest in a nutshellREST antipatternREST for the mobile world

HowHTTP cache fault-tolerance, downtime-availabilityESI Atom + Hypermedia controls

Whyperformancesevolution costadaptability

Sorry for the ugly slide.

There will be others.Really sorry.

A nutshellin (a mobile) peace

Let's go back!

http://www.ics.uci.edu/~fielding/pubs/dissertation/rest_arch_style.htm

2000Fielding's dissertation:

REpresentational

Transfer

REST in a nutshell:

1. Client <> Server

REST in a nutshell:

2. Stateless

easy toscale

Recover andfailoverparadise

What about the user session?

Must die

3. Cacheable

REST in a nutshell:

When dealing with safe methods,the response should be able to tell the client,

or whatever stands behind the request,how to cache it.

REST in a nutshell:

4. Layered system

REST in a nutshell:

5. Uniform interface

Uniform interfacehierarchic resource identification

Verbs to perform operations

manipulation through representation

HATEOAS

Richardson maturity model

hierarchic resource identification

manipulation through representation

HATEOAS

Really well explained by Fowler: http://martinfowler.com/articles/richardsonMaturityModel.html#level0

HATEOAS

mess0.

0Using HTTP

Without giving a f***

HATEOAS

mess0.1.

1mytastyproduct.com/users

mytastyproduct.com/users/1/licenses/4

HATEOAS

mess0.1.2.

HATEOAS

mess0.1.2.

3. GOD

http://www.slideshare.net/trilancer/why-hateoas-1547275

Hyperlinks

Hypermedia formats

http://amundsen.com/hypermedia/

Single entry point

Uniform interface is interesting.

Everyone seem to have its own RESTful "service".

But no one seem to entirely implement a uniform interface.

Uniform interface is interesting.

Everyone seem to have its own RESTful "service".

But no one seem to entirely implement a uniform interface.

That means... ...?

No RESTful

But don't be too religious.

REST gets raped everyday, get over it.

( a few ) ANTIPATTERNSin (a mobile) peace

"REST is about

cool URI design"

http://apple.com/users/1/licenses/4.json

"REST is about

cool URI design"

http://apple.com/users/1/licenses/4.json

http://apple.com/site/en_US/showUsers.jsp?uid=1&license=4

is OK too

"cool URIs help youthink in term of resources"

- David Zuelke

and, by the way

a URI should neverlocate different resources

while a resource could belocated by different URIs

2URIs (bis)

REST follows a URI schema

GET /users POST /users PUT /users/{id} DELETE /users/{id} ...

REST follows a URI schema

GET /users POST /users PUT /users/{id} DELETE /users/{id} ...

URI templates suck, some say

what if you change yourURL?

Yeah, client is broken

RESTful clients shouldbe driven by service'shypermedia controls

Roy Fielding : http://roy.gbiv.com/untangled/2008/rest-apis-must-be-hypertext-driven

3Formats

a representation variesbased on the format

Can be:application/xmlapplication/jsonaudio/mp4image/png

but also:text/dnsvideo/vnd.motorola.videotext/uri-list

dear JSON, by the way

JSON is evil

{ "date": "2011-01-01", "stock": "100", "price": "12"}

The business evolves

{ "date": "2011-01-01", "stock": "100", "price": [ {"currency": "EUR", "amount": "12"}, {"currency": "USD", "amount": "10"} ]}

Credits: http://twitter.com/#!/odracci

Yeah, client is broken

Everything is a tradeoff

4POST is cool

said SOAP 1.1

loosing meaningful verbs at the protocol level

nothing cacheable by default

loosing meaningful verbs at the protocol level

nothing cacheable by default

what about bookmarking?

5500 is your friend

said SOAP( again )

GET /users/300Host: www.example.com

HTTP/1.1 500 Internal Server ErrorEtag: 1234X-Powered-By: php/5.3...

The record cannot be found

HTTP/1.1 500 Internal Server ErrorEtag: 1234X-Powered-By: php/5.3...

The record cannot be found

The HTTP protocol is awesome,and lets you return meaningful anduniversally-understood status codes

404 Not Found

OMG Link is broken?

202 Accepted

You get an immediate OK, and the operation will hopefully complete

412 Precondition Failed

Want money?.. Got money?

The serious s**tin (a mobile) peace

How do Iimplement

thisgoodness?

caching & scalability

HTTPyour long-time friend

Shared/proxy

Shared/reverse proxy

Types of cache

Shared/proxy

Types of cache

Shared/proxy

Types of cache

Shared/proxy

Types of cache

on the server side

Proxy Reverse proxy

http://www.codeproject.com/KB/aspnet/ExploringCaching.aspx

There is something cool about caching softwares.

Free as free beer

...but the server should take advantage of them

( the boring part were you need to write code )

and here are a few ways to do so, using

expiration

validation

expiration

validation

invalidation

expiration

validation

invalidationwe will se why

Expiration

GET / HTTP/1.1Host: www.example.comExpires: 0

GET / HTTP/1.1Host: www.example.comExpires: Tue, 15 Nov 1994 01:00 GMT

GET / HTTP/1.1Host: www.example.comCache-Control: max-age=60, public

Cacheable for 60 seconds

GET / HTTP/1.1Host: www.example.comCache-Control: max-age=60, public

Cacheable by both local and shared caches

GET / HTTP/1.1Host: www.example.comCache-Control: stale-if-error=600, stale-while-revalidate=600

fault-tolerant

available during downtime

available during revalidation

Validation

GET / HTTP/1.1Host: www.example.comEtag: 1234

an identifier for your response

GET / HTTP/1.1Host: www.example.comIf-None-Match: 1234

the browsers asks you if it has been modified

Conditional requests

Calculating an Etag is cheaper than generating a full MVC response

HTTP/1.1 304 Not Modified

GET / HTTP/1.1Host: www.example.comLast-Modified: Tue, 15 Jan 2011 12:00:00 GMT

tell the client about the latest change

GET / HTTP/1.1Host: www.example.comIf-Modified-Since: Tue, 15 Jan 2011 12:00:00 GMT

the client asks you if it has been modified since the last time

Conditional requests

Calculating a date is cheaper than retrieving an entire object

HTTP/1.1 304 Not Modified

Invalidation

The web is not meant for invalidating data.

Server should not be able to keep clients' state, otherwise they wont scale well.

That's why long-polling and endless connections haven't had big success dealing with caching.

but hey, you say

HTTP's cache fails when dealing with really dynamic pages, because consumers will always have to hit the origin server, although a part of the page would be cacheable ( header and

footer, for example )

ESI was built for thathttp://www.w3.org/TR/esi-lang

Edge Side IncludesA de facto standard for bla bla bla...

Server side includes ( not SSI! ) usually handled by the architecture's ESI processor.

http://www.w3.org/TR/esi-langhttp://www.w3.org/TR/edge-arch

<esi:include src="http://whymca.org/talks/1" />

This is a response

15 seconds cache

30 minutes cache

and hey, Varnish is a reverse proxy implementing what you need of the ESI specification

take 2, pay for 1

So what does HTTP cache is meant to solve?

Less work

because the hard work is delegated to the browser/proxy

http://www.flickr.com/photos/snakphotography/5004775320/sizes/o/in/photostream/

evolve

because cache is abstracted from the application

loose coupling

because caching is bound to the protocol, HTTP, not to your implementation ( Sf, RoR, Django )

adaptability & durability

Hypermediaanother long-time friend

Linksoutrageously semplifying

Atomis your friend

http://www.xml.com/lpt/a/1434

POST /usersHost: www.example.com

HTTP/1.1 201 CreatedHost: www.example.comEtag: 1234X-Powered-By: php/5.3Location: /users/1

HTTP/1.1 301 Moved permanentlyHost: www.example.comLocation: /users

HTTP/1.1 201 CreatedHost: www.example.comEtag: 1234X-Powered-By: php/5.3Location: /newusersdatabase/1

Helps refactoring legacy stuff indeed :)

consumers of your API are able to followthe changes of your design

Clients are too importantto break'em

and here comes a controversial part...

Like it or not,

XML is a friend of the non BC-breaking evolution

http://www.slideshare.net/Wombert/xml-versus-the-new-kids-on-the-block-phpbnl11-20110129http://www.odino.org/320/long-live-xml-too-sorry-for-json-fanboyz

BTW<xml...> <product...> <price>25</price> </product></xml>

BTW<xml...> <product...> <price currency="EUR">25</price> <price currency="USD">23</price> </product></xml>

As said, everything is a tradeoff

Choose the media typefor your needs

No need to be religious. Ever.

Why beingin (a mobile) peace?

everything seems cool

why REST?

Performances

Scalability

http://articles.sfgate.com/2011-02-20/opinion/28613184_1_news-network-cable-and-satellite-website

http://tech.groups.yahoo.com/group/rest-discuss/message/17370

+2.500%traffic

Durability

"REST is software design on the scale of decades: every detail is intended to promote software longevity and independent evolution. Many of the constraints are directly

opposed to short-term efficiency. Unfortunately, people are fairly good at short-term design, and usually awful at long-term design. "

Roy Fielding

Put a bit of REST

everywhere

Rules of good design

amazon.it

Alessandro Nadalin

Alessandro Nadalinodino.org

@_odino_

Thanks

@_odino_

Creditshttp://www.flickr.com/photos/larachris/16564077/sizes/o/in/photostream/

http://www.flickr.com/photos/ashatenbroeke/4367373081/sizes/z/in/photostream/http://www.flickr.com/photos/yourdon/3140270189/sizes/l/in/photostream/http://www.flickr.com/photos/jox1989/4964706072/sizes/l/in/photostream/http://www.flickr.com/photos/brainfg/168506259/sizes/o/in/photostream/

http://www.flickr.com/photos/norte_it/3897091546/sizes/o/in/photostream/http://www.zdnet.com/blog/service-oriented/soap-versus-rest-a-matter-of-style/3568

http://www.flickr.com/photos/turtlemom_nancy/2046347762/sizes/l/in/photostream/http://www.flickr.com/photos/juanpg/3333385784/sizes/z/in/photostream/http://www.flickr.com/photos/congvo/301678287/sizes/l/in/photostream/

http://www.flickr.com/photos/ihasb33r/2573196546/sizes/z/in/photostream/http://www.flickr.com/photos/martin_heigan/4544138976/sizes/o/in/photostream/

http://www.flickr.com/photos/cknara/4195099999/sizes/o/in/photostream/http://www.flickr.com/photos/1080p/3076529265/sizes/l/in/photostream/

http://www.flickr.com/photos/adamrice/280300202/sizes/l/in/photostream/http://www.flickr.com/photos/tomer_a/541411897/sizes/o/in/photostream/http://www.flickr.com/photos/subpra/4514008262/sizes/l/in/photostream/

http://www.flickr.com/photos/lippincott/2539720043/sizes/l/in/photostream/http://www.flickr.com/photos/rawryder/5086090931/sizes/l/in/photostream/http://www.flickr.com/photos/robboudon/5312731161/sizes/l/in/photostream/

http://www.flickr.com/photos/bc-burnslibrary/4158243488/sizes/o/in/photostream/http://www.flickr.com/photos/13606325@N08/2416993706/sizes/o/in/photostream/

http://www.flickr.com/photos/neothezion/5135841069/sizes/l/in/photostream/http://www.flickr.com/photos/planetschwa/2494067809/http://www.flickr.com/photos/thomasthomas/258931782/

http://www.flickr.com/photos/rustyboxcars/2629631562/sizes/l/in/photostream/http://www.flickr.com/photos/ell-r-brown/4138727474/sizes/l/in/photostream/http://www.flickr.com/photos/noah123/5082076630/sizes/z/in/photostream/http://www.flickr.com/photos/jungle_boy/220181177/sizes/l/in/photostream/

http://www.flickr.com/photos/prettydaisies/872539081/sizes/l/in/photostream/http://www.flickr.com/photos/kaptainkobold/76256150/sizes/o/in/photostream/

http://www.flickr.com/photos/uomoincravatta/1438372865/sizes/z/in/photostream/

rest in ( a mobile ) peace @ whymca 05-21-2011

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