Large scale rails applications

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Large scale Rails applications Florian Dutey

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www.strikingly.com

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www.sxl.cn

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2007 1.2.3

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Fat Models Skinny Controllers

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If it’s not a controller job, leave it to the model.

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If it’s not a controller screwdriver job, leave it to the model hammer.

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User specs (1) • User can signup through site / API • When a user signup, we send an email to conﬁrm it’s email address

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User specs (2) • Admins can create users through admin tool • When admin create a user, we auto-generate the password and send it through email

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User specs (3) • We have a partnership with another solution (A) and we need to share our users • We will consume A’s API to collect users and insert them in our DB • When we register a new user this, we don’t send any email (email is assumed conﬁrmed already and we can grab their password from API).

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Rails doesn't scale!

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Rails is NOT an application framework

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Rails is a web framework!

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Application Http Request Response

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Request Router Controller Response View Models

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Request Router Controller Response View Models Business logic

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Request Router Controller Response View Business logic ? ? ? ? ? Models

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Services Business logic Forms Policies Queries Adapters Models

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Services Forms Policies Queries Adapters Models Business logic

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Services (1) Describe processes

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Services (2)

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Services (3)

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Services (4) Create != Signup

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Services (5)

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Services (6)

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Services (7)

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Services (8) User::SignupService Payment::SignupService user/signup_service_spec Payment::SignupService payment/signup_service_spec

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Services Forms Policies Queries Adapters Models Business logic

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Forms (1) Convert inputs in Domain language

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Forms (2) USER email password

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Forms (3)

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Forms (4)

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Forms (5)

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Forms (6) User email password User::Profile user_id first_name last_name User email password first_name last_name

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Forms (7) accepts_nested_attributes_for

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Forms (8)

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Forms (9)

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Forms (10)

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Services Forms Policies Queries Adapters Models Business logic

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Policies (1) Describe permissions

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Policies (2)

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Policies (3)

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Policies (4)

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Services Forms Policies Queries Adapters Models Business logic

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Queries (1) Describe how to access data

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Queries (2)

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Queries (3)

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Services Forms Policies Queries Adapters Models Business logic

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Adapters (1) Translate DSL into another

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Adapters (2) User email password first_name last_name Recurly

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Adapters (3)

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Adapters (4) It’s about languages

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Adapters (5) 3rd party API language Client Http request Ruby method

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Adapters (6) Client API Language Adapter DSL Application

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Adapters (7)

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Adapters (8) PaymentManager RecurlyAdapter StripeAdapter RecurlyClient StripeClient

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Benefits • Easy to test (mock client responses) • New provider => new adapter • Easy to migrate • Fake adapters for integration servers

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Services Forms Policies Queries Adapters Models Business logic

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Models (1) Data (& persistency)

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Models (2) If it doesn’t fit in models …

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Models (3) Then it doesn’t fit in models!

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Models (4)

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What if it doesn’t fit anywhere?

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It’s not a perfect solution, just a guide

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Principles • Single Responsibility Object • Plain Old Ruby Objects • Inversion Of Control • Stateless Objects • Domain Specific Modeling

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Single Responsibility Principle (SRP)

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Not SRP

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SRP

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User email password first_name last_name address_1 address_2 zip_code city country

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User email password User::Profile user_id first_name last_name User::Address user_id address_1 address_2 zip_code city country

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“Make everything as simple as possible, but not simpler.” Albert Einstein

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Plain Old Ruby Objects (PORO)

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PORO

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Not PORO

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Inversion of controls

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Separate what and when

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Why? • Separate responsibilities (SPR) • Remove strong dependencies • Easier to test and debug

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Stateless objects

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Stateless

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Statefull

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Statefull Stateless

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Domain Specific Modeling

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Router Controller Domain API language Domain Specific Modeling View API language

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Conclusion

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Rails is a prototyping framework!

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Pros • Easier to browse and discover • More flexible • Easier to test • Easier to debug • Agnostic (from Rails)

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Cons • Harder to design • More time spent on code architecture • Write more code, more tests • Write integration tests (IOC)

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Small apps

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Soft transition • Code convention • Focus on data and API • Express everything in Domain Language • Write adapters early • Prepare to drop Rails prototyping tools ASAP

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Big apps

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More tips • If it doesn’t fit anywhere, think twice • If it still doesn’t fit anywhere, you need a new layer • Check what Java / React community does