Working effectively at scale

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Working e!ectively at scale

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Francisco Díaz franciscodiaz.cl - @fco_diaz

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Startups 2011 - 2017

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Airbnb 2017 - today

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organizations ... are constrained to produce designs which are copies of the communication structures of these organizations — Conway's law

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How do you divide your codebase?

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Architectural layer

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User Flow

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What about Airbnb?

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1 million lines of Swift

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~80 commits to master on any given day to the repo (Android + iOS)

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Bigger buckets

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A user should be able to wishlist a listing from the booking flow

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How do they relate with each other?

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50 min local clean builds

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~30 min !

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Buck HTTP Cache https://github.com/airbnb/BuckSample

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~5 min !

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Dependency inversion

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‣High-level modules should not depend on low- level modules. Both should depend on abstractions. ‣Abstractions should not depend on details. Details (concrete implementations) should depend on abstractions.

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A user should be able to wishlist a listing from the booking flow

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Easy! WishListDataSource + interface!

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WishListDataSource is still visible

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Socializing best practices

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+60 iOS developers

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Automating best practices

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Groups Modules

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Groups Modules Module Types

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Module Types Feature + Interface Service + Interface

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Feature A screen or a flow in the app

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Service Manage shared state or resources

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How do we enforce these best practices?

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/services /service_interfaces /features /feature_interfaces

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def service_interface( name, deps): max_visibility = [ "//ios/feature_interfaces/...", "//ios/features/...", "//ios/service_interfaces/...", "//ios/services/...", ]

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service_interface( name = "Networking", deps = [ "//ios/service_interfaces/Logging", ], )

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feature( name = "Booking", deps = [ "//ios/service_interfaces/Networking", "//ios/service_interfaces/WishListService", ], )

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iOS Platform

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Module creation needs to be easy

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rake make:module

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> Provide the type of module you want to create: 1: Non Platform 2: Feature 3: Feature Interface 4: Service 5: Service Interface 4 > New module name: Swiftable > Provide a high level description of this module: This is a module to present at Swiftable

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Buck Human readable dependencies https://github.com/airbnb/BuckSample

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feature( name = "Booking", deps = [ "//ios/service_interfaces/Networking", "//ios/service_interfaces/WishListService", "//ios/feature_interfaces/HelpCenter", ], )

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Feature A screen or a flow in the app

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Dev Apps

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~1 min Dev Apps

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Big buckets Small playgrounds

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How do we get there?

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~100 modules One module type: /libraries

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libraries/AirbnbBooking libraries/AirbnbBusinessTravel libraries/AirbnbHelpCenter libraries/AirbnbListings libraries/AirbnbNetworking libraries/AirbnbWishLists ...

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Before iOS Platform /libraries

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On the iOS Platform /services /service_interfaces /features /feature_interfaces

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How to get everybody on the iOS Platform?

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Remove libraries/ and start over

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Progressively migrate

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Let's migrate WishLists Data Source

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libraries/WishLists

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What are the dependency rules for libraries/?

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Inbound dependencies Outbound dependencies

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Inbound dependencies Outbound dependencies

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The interface module has stricter rules

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Migrate all the call sites

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As the owner of WishLists We don't control these

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Calculated tech debt

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Inbound dependencies Outbound dependencies

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we know our usage of Networking

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We control our dependencies

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Allow inbound dependencies from libraries/ Don't allow outbound dependencies to libraries/

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libraries/ has access to the iOS Platform

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The iOS Platform doesn't have access to libraries/

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Code on the iOS Platform has good boundaries

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while we allow for easier migration

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def service_interface( name, visibility = []): max_visibility = [ "//ios/feature_interfaces/...", "//ios/features/...", "//ios/service_interfaces/...", "//ios/services/...", ] add_visibility_for_legacy_module_structure(max_visibility)

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def add_visibility_for_legacy_module_structure(visibility): visibility.extend([ "//ios/libraries/...", ])

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We started migrating from the bottom up

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Try it ourselves !rst

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Pilot with others teams

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Should I implement this?

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Most likely NO

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There's no silver bullet

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Adapt

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Summary 1. Figure out where you're struggling 2.Create and document best practices 3.Automate best practices where needed

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¡Gracias! franciscodiaz.cl/talks