Applying Evolutionary Architecture on a Popular API

Wednesday, March 6, 13

Applying Evolutionary Architecture on a

Popular API

phil calçado@pcalcado

http://philcalcado.com

QCon London Session Code: 1603Wednesday, March 6, 13

Wednesday, March 6, 13

Wednesday, March 6, 13

> 50K registered client apps

~ 180 million users / month

~5 years old

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Wednesday, March 6, 13

API controllers UI controllers

domain logic

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http://bit.ly/building-the-next-soundcloud

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API controllers UI controllers

domain logic

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API controllers

UI controllers

domain logic

internet

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a new platform while keeping the old one

running?

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WARNING:THIS IS

WORK IN PROGRESS

http://bit.ly/work-at-soundcloud and you can help us ;)

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DO NOT BREAK CLIENT APPS

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separate application

from domain

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A set is a collection of

your own sounds

ClassicSoundCloud

NextSoundCloud

A set is a collection of

your own sounds

Wednesday, March 6, 13

A set is a collection of

your own sounds

ClassicSoundCloud

NextSoundCloud

A set is a collection of

your own sounds

A set is a collection of

sounds

SoundCloudAPI

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API controllers

UI controllers

domain logic

internet

Wednesday, March 6, 13

API controllers

UI controllers

domain logic

internet

domain logic domain logic

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applications enforce their own business rules

domain enforces “global” rules

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applications enforce their own business rules

domain enforces “global” rules

(accidents happen...)

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how to add/change features on the fly?

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attempt #1: identify “official” apps

- too easy to spoof- abused by spammers- Android and iOS can’t easily rotate secrets

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attempt #2: namespace endpoints

- “experimental” endpoints would link to regular ones but never be linked back- toyed with “lifted” hyperlinks, not enough time for launch

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attempt #3: just use feature flags

- works ok for logged in users

- system is a little monster now, and ruby is not very good with numbers. rewriting in scala

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SPLITTING THE MOTHERSHIP

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define internal protocols

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micro-services- couple thousands lines of code

- mostly JVM-based, JRuby, Clojure and Scala

- more about this at the SoundCoud pub night tomorrow: http://lanyrd.com/2013/soundcloudpub/ (Walrus Pub Waterloo)

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HTTP+JSON & AMQP for most stuff

- moving AMQP usage for event broadcasting, as opposed to messaging

- no internal HTTP caching (yet?)

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make it easy to get stuff in prod

- heroku-like deployment system

- tending towards twitter stack (Finagle) for I/O

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URNs, not IDs

soundcloud:sounds:123

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URNs, not IDs- everything addressable has a URN, some have URLs

- Mapping depends on context, e.g. given object may have a public URL and an internal URL

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<3 hypermedia

- can easily remove things from the main app without breaking clients, just some HTTP 303s

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OPTIMISE ALL THE THINGS!!11!

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twitter moving back to server rendering...?

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not too bad, actually

- besides load balancers vs. increase in number of requests per page

http://backstage.soundcloud.com/2012/08/evolution-of-soundclouds-architecture/

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the actual problems

- number of requests from Next keeps increasing, page load affected- very different behaviour depending on the client app

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API controllers

UI controllers

domain logic

internet

domain logic domain logic

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API controllers

internet

UI controllers

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attempt #1: optmising proxy for clients

UI controllers

domain logic

internet

domain logic domain logic

API controllers

Proxy

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attempt #1: optmising proxy for clients

- still leverage public API- API has to know about how things behave in different clients

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attempt #2: specialised back-end for official

clients

UI controllers

domain logic

internet

domain logic domain logic

Specialised Back-end API controllers

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attempt #2: specialised back-end for official

clients

- each official app has its own back-end facade- no rendering, just data- public API becomes just one of them- front-end heavy teams can just script a common core using JRuby

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NEXT STEPS

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what we are looking at

- dataflow programming for the specialised back-ends

- ProtocolBuffers for Android

- make the mothership just a back-end service, not exposed to the Internet

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phil calçado

http://philcalcado.com@pcalcado

www.soundcloud.com

Wednesday, March 6, 13