Why Architecture Matters

Why Architecture mattersLars Jankowfsky, swoodoo.com

Freitag, 20. März 2009

PHPCon Italia 2009

Lars Jankowfsky, swoodoo.com

Why Architecture matters

Lars Jankowfsky

• CTO swoodoo.com

• XP, agile development fanatic

• developing since 15+ years

• php since php/fi

• Software Architect > 10 years


Architecture



Zend Framework

symfony

cakePHPezComponents


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long project lifetime


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long project lifetime• code aging


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long project lifetime• code aging

• big ball of mud


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continuous maintenance


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continuous maintenance• strong dependency -> „co-dependency“


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• deployment


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• deployment

• scaling


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Blaine Cook, Twitter's lead architect:

„For us, it’s really about scaling horizontally - to that end, Rails and Ruby haven’t been stumbling blocks, compared to any other language or framework. The performance boosts associated with a “faster” language would give us a 10-20% improvement, but thanks to architectural changes that Ruby and Rails happily accommodated, Twitter is 10000% faster than it was in January.“


Success


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Success


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Success

• D.R.Y. == Do Not Repeat Yourself


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Success


• Single responsibility principle


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Single responsibility principle


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• "if it generates XML then it should not generate HTML"


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• "if it generates XML then it should not generate HTML"

• "if you want to serialize to xml do not create "toxml" Method, instead pass $this to the XMLExporter"


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Success


• Single responsibility principle

• K.I.S.S.


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K.I.S.S.


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K.I.S.S.

• think in advance but don‘t think too complex


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K.I.S.S.


• before making any generalisation have at least two cases


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K.I.S.S.


• before making any generalisation have at least two cases

• the more abstractions the easier you can change it later


Developing


Art


Evolution


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Evolving Architecture


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• Y.A.G.N.I. == You Ain‘t Gonna Need it


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• Y.A.G.N.I. == You Ain‘t Gonna Need it

• Without refactoring there is no evolution


Principle of „bad smell“


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Bad smells?


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Bad smells?

• Do maintenance cost keep increasing?


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Bad smells?


• Simple features need too long to be implemented


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Bad smells?


• Simple features need too long to be implemented

• Small changes ripple through your system



dead code


dead code

data classes


comments „what not why“

dead code

data classes


comments „what not why“

long methods

dead code

data classes


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Bad Smells

• http://martinfowler.com/bliki/CodeSmell.html

• http://www.codinghorror.com/blog/archives/000589.html


http://martinfowler.com/bliki/CodeSmell.html

http://martinfowler.com/bliki/CodeSmell.html

http://www.codinghorror.com/blog/archives/000589.html

http://www.codinghorror.com/blog/archives/000589.html

Separation


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Layered Architecture


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• separation of concerns


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• If they can live without each other - why to couple them?


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• Find the boundaries and cut mercilessly.


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• Do not bypass any layer!


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• Do not bypass any layer!

• Separate modules/classes or go SOA


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SOA


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SOA• Pro: makes scaling very easy


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• Pro: clear defined boundaries, no violations possible


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• Pro: perfect for refactoring


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• Pro: Deployment benefits


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• Pro: Deployment benefits

• Con: integration testing gets more difficult


Database



ZendDb

PDO

ADOdb

propel


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Database


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Database

• you need a database access layer


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Database


• go ORM if possible (performance!)


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Database



• Active Record has business logic


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Database



• Active Record has business logic

• business layer - not abstraction layer


Db Abstraction Layer PDO, ADOdb, ZendDb....



Object Layer Table Data Gateway Pattern




Business LayerActive Record




Business LayerActive Record

function giveMeMyData()


MVC


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Controller


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Controller• Common mistake: business logic in controller


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• Keep it out! Otherwise you will end with SQL in controller


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• I/O mapping to the model and view only


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• I/O mapping to the model and view only

• Kick Ass!


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View


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View• Use a template engine. Watch performance!


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• No business logic in the template/html


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• No business logic in the template/html

• Kick Ass!


TDD


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TDD• enforces layered Architecture





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TDD

• enforces layered Architecture

• use continuous integration (e.g. cruise control)


Unit Tests


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Unit Tests


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Unit Tests• test a single class


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• do not touch:


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• do not touch:

- database


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• do not touch:

- database

- network


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• do not touch:

- database

- network

- (files)


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• do not touch:

- database

- network

- (files)

• use mocks/stubs


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• do not touch:

- database

- network

- (files)

• use mocks/stubs

• provide fast feedback


Unit Tests

Integration Tests


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Integration Tests


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Integration Tests• test several classes


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• test communication between classes/modules


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• test communication between classes/modules

• they test full components


Unit Tests

Integration Tests

Acceptance Tests


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Acceptance Tests


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Acceptance Tests• test functionality from „outside“


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• often build from „user stories“


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• often build from „user stories“

• usually done with Selenium


what if fixture/mock preparation are much larger than tests?


what if your tests run for hours ?


framework !== software architecture


evolve your architecture


split your application into layers


enforce proper usage of MVC


wrap database access


utilize test driven development


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Thank you for your interest!

http://joind.in/talk/view/232


mailto:[email protected]

mailto:[email protected]

Technology

Why Architecture Matters