How Fervo builds web apps

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How Fervo builds web apps Magnus Nordlander

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Magnus Nordlander • PHP consultant and CEO with Fervo • Worked with PHP for well over 10 year, Symfony for over 9 years.

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• Small consultancy specialized in   modern PHP, Symfony in particular • Three PHP consultants, two  Symfony certed • Read more at fervo.se

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Index • Technology radar • Tech Stack • Development methodology • Software architecture

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Index • Demo of our code structure in practice • Questions

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Preface • I’m gonna introduce a lot of concepts • I could easily spend 45 minutes per concept or do a multi-day workshop on this • My goal is to pique your interest, so that you want to learn more

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Preface • Small projects require less structure • Some of the advice within this presentation is more appropriate for large projects • Your mileage may vary

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Technology Radar

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Maturity • Generally recommended • Under trial • Promising • Interesting

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Tech stack

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Tech Stack • PHP 7 is generally recommended, subsetphp is interesting • HHVM has been promising for a long time, but as PHP7 has become better, the need has diminished • Linux is generally recommended for servers • We prefer Postgres, but MySQL is ﬁne too

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Tech Stack • Redis is great • Several mature Document oriented databases, but which one to choose depends • ElasticSearch is awesome for search • We love Heroku, and we're fond of AWS.

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Tech Stack • We're all using Docker for our dev environments • Docker for Mac is interesting, but not good enough yet • Docker in production is very interesting, and we hope to use it in a client project soon

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Tech Stack • We generally recommend php-fpm • There have been interesting developments for a long time in serving requests from within PHP • Leach (0MQ) • ReactPHP / PHP-PM • PHPFastCGI

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Development methodology

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Development methodology • We don't believe in waterfall • We generally recommend BDD, both Story BDD and Spec BDD • Communication and collaboration is key

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Communication

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BDD • Behavior driven development • TDD “done right” • TDD + DDD + OOA&D => BDD • Many pay lip service to testing, BDD gives immediate rewards, encouraging adoption

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Story BDD • Capture business requirements in a testable format • Written in business readable, ubiquitous language • Behat is a great tool for Story BDD, just make sure you run Behat 3

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Story BDD

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Spec BDD • Speciﬁes what a class should do and how it should interact with other classes • PHPSpec is excellent • Makes it painfully obvious when you’re violating SOLID

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Software architecture

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Software architecture • Your domain code is at the center of your application • Web framework for integrating your domain code with the web • CLI framework for giving your domain code a CLI

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Domain code • Written like a library • We generally recommend Command-Query Separation • We also generally recommend using events • Commands and events are messages

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Domain code • Take a DDD approach to modeling your domain • Analyze your problem domain, create a model • Entities, Value objects, Aggregates, Domain events, Services, Repositories and Factories • Event storming looks cool, but we’ve never had the opportunity to do it

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Messages • Imagine you’re the emperor of Rome. You like to sit in your palace. • When your army has conquered new territory, you are passed a scroll with the details of the event • When you need to quash a rebellion to maintain pax romana, you send a scroll with your command to the governor

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Messages • Messages differ mainly in intent • Events are informative in nature, and they are passed to anyone whom they concern • Commands are imperative in nature, and they are only passed to their respective command handler

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–The Ofﬁce “Look, it doesn't take a genius to know that any organization thrives when it has two leaders. Go ahead, name a country that doesn't have two presidents. A boat that sets sail without two captains. Where would Catholicism be without the popes?

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Messages • Messages are just small PHP class instances that can be passed around • Immutability is king • Messages do not have return values

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Messages • To handle a message, we use a message bus • Commands are handled by a command bus • Exactly one handler per command • Events are handled by an event bus • Zero or more event listeners

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SimpleBus • Message bus library written by Matthias Noback • Messages and handlers are just your own PHP classes • Also supports asynchronous message handling

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SimpleBus

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SimpleBus

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SimpleBus

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Domain Code • Another interesting pattern is the Speciﬁcation pattern • RulerZ • Under trial

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Speciﬁcation Pattern • All members who have the gold status • SELECT * FROM members WHERE status = ‘gold’

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Speciﬁcation Pattern • Not very object oriented • Ties your query builder to both your database engine and your database scheme • Imagine having to implement a rules engine

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Speciﬁcation Pattern

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Speciﬁcation Pattern

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Web frameworks • Integrate your domain code into the web • A controller takes an HTTP request, returns an HTTP response • Thin glue to your domain • Your domain code does not have any dependencies on your web framework

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Web frameworks • Modern frameworks are many things • In Symfony, the web framework is really only HttpKernel and HttpFoundation • Web related components (security, form) • Glue components (dependency injection) • Misc (yaml, ldap)

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Frameworks • Depending on one of the miscellaneous components is ﬁne if it makes sense. • In Symfony, we have the concept of a bundle, which integrates a library with the framework • Your domain code is a library

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Dependency Injection • Do not use the Dependency Injection Container as a service locator.

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Dependency Injection • I’m serious.

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Dependency Injection • Separate your domain code and your bundle • Your domain code should know nothing of your DI container • Most of your bundle should know nothing of your DI container • Bundle extension and compiler passes mostly

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Dependency Injection • Symfony controller base class is not a good role model • Luckily, it’s optional

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Demo

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Questions?

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Contact • @drrotmos on Twitter • [email protected] • Want help? We’re a consultancy, so give me a call • https://www.fervo.se