REST in peace: a handbook of software waste @ Jazoon 2011 06-22-2011

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REST in peaceA handbook of software waste

Alessandro Nadalin

DNSEE

430

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2

AGENDA

> Vol. 1: REST in a nutshell

– Tenets

– Antipatterns

> WWW: a tremendous architecture

– Stateless

– Layered

– Cacheable

– Fault-tolerant

– Failure-prone

> Vol. 2: To the rescue

– HTTP cache

– ESI

– HATEOAS

> Vol. 3: REST is not a panacea

– SOAP

– Limited horizon

– Agile development

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Sorry for the ugly slide.

There will be others.Really sorry.

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REST in a nutshell:

1. Client <> Server

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REST in a nutshell:

2. Stateless

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3. Cacheable

REST in a nutshell:

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REST in a nutshell:

4. Layered system

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REST in a nutshell:

5. Uniform interface

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9

And obviously nobody had a clue

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10

ANTIPATTERNS

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1URIs

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"REST is about

cool URI design"

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

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"REST is about

cool URI design"

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

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

is OK too

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but

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cool URIs help youthink in term of resources

David Zuelke

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2URIs (bis)

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

REST follows a URI schema

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

REST follows a URI schema

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what if you change yourURL?

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Yeah, client is broken

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RESTful clients shouldbe driven by service'shypermedia controls

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

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HATEOAS

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3POST is cool

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said SOAP

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said SOAP

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loosing meaningful verbs at the protocol level

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loosing meaningful verbs at the protocol level

nothing cacheable by default

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loosing meaningful verbs at the protocol level

nothing cacheable by default

what about bookmarking?

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30

Have a break

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31

The WWW

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32

the largest data-exchange network on the planet

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33

And meanwhile, at Facebook...

12TB of new data every day(1 year ago)

500 million users

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34

via HTTP, baby!

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HTTP in a nutshell:

1. Client <> Server

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HTTP in a nutshell:

2. Stateless

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http://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html

3. widespread cache spec

HTTP in a nutshell:

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HTTP in a nutshell:

4. Layered systemOrigin server

Reverse proxy

Great chinese (fire)wall

Company proxy

Lao Tze Song office's laptop

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HTTP in a nutshell:

5. it is the uniform interfacebetween clients and servers

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40

HTTP bleeds REST

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Vol.2Implementing all this goodness

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1.

caching & scalability

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Caching withExpiration

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HTTP/1.1 200 OKHost: www.example.comExpires: 0

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HTTP/1.1 200 OKHost: www.example.comExpires: 0

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HTTP/1.1 200 OKHost: www.example.comExpires: Tue, 31 Jan 2011 01:00 GMT

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HTTP/1.1 200 OKHost: www.example.comCache-Control: max-age=60, public

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HTTP/1.1 200 OKHost: www.example.comCache-Control: max-age=60, public

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HTTP/1.1 200 OKHost: www.example.comCache-Control: max-age=60, public

Cacheable for 60 seconds

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

Cacheable by both local and shared caches

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HTTP/1.1 200 OKHost: www.example.comCache-Control: stale-if-error=600, stale-while-revalidate=600

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HTTP/1.1 200 OKHost: www.example.comCache-Control: stale-if-error=600, stale-while-revalidate=600

fault-tolerant

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HTTP/1.1 200 OKHost: www.example.comCache-Control: stale-if-error=600, stale-while-revalidate=600

available during downtime

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HTTP/1.1 200 OKHost: www.example.comCache-Control: stale-if-error=600, stale-while-revalidate=600

available during revalidation

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Caching withValidation

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HTTP/1.1 200 OKHost: www.example.comEtag: 1234

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HTTP/1.1 200 OKHost: www.example.comEtag: 1234

an identifier for your response

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

the browsers asks you if it has been modified

Conditional requests

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HTTP/1.1 304 Not Modified

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Calculating an Etag is cheaper than generating a full MVC response

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but hey, you say

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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 )

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Nope

Nope

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

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Edge Side Includes

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

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<esi:include src="http://jazoon.com/talks/1" />

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<esi:include src="http://jazoon.com/talks/1" />

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<esi:include src="http://jazoon.com/talks/1" />

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15 seconds cache

1 day cache

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<esi:include src='tweets.html' />

<esi:include src='footer.html' />

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

take 2, pay for 1

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So what does HTTP cache is meant to solve?

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Less work

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because the hard work is delegated to the browser/proxy

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

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evolve

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because cache is abstracted from the application

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loose coupling

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

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2.

adaptability & durability

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Hypermediaanother long-time friend

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Linksoutrageously semplifying

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<link rel="payment" href="/checkout" type="text/html" ... />

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<link rel="payment" href="/checkout" type="text/html" ... />

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<link rel="payment" href="/checkout" type="text/html" ... />

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<link rel="payment" href="/checkout" type="text/html" ... />

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

POST /usersHost: www.example.com

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

POST /usersHost: www.example.com

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

POST /usersHost: www.example.com

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

POST /usersHost: www.example.com

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

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everything seems cool

But why REST?

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Pros

Performances

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Pros

Scalability

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Pros

Durability

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"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

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Put a bit of REST

everywhere

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Rules of good design

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Use natives=

Eliminate waste

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The wheel!

HTTP - 1991~1997

REST - 2000

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Vol.3REST is not a panacea

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SOAPNo need to re-invent the wheel: if you need to do SOAP integration, SOAP

is the way.

If you have a completely functional SOAP service, no - apparent - need to rewrite it RESTful from scratch.

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AGILE

The last responsible moment conflicts with REST.

But quality enhance agility: REST is quality.

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LIMITED HORIZON

My blog won't ever be RESTful.

But incremental design, bare it in mind.

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Alessandro Nadalin odino.orgDNSEE @_odino_Rome github.com/odino

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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/

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

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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/

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