Mobile Architecture at Scale

1. Mobile Architecture at Scale Why and how we built a new architecture used by hundreds of engineers, all in one codebase 18 Jan 2018 Gergely Orosz, Engineering Manager, Payments, Uber

2. Engineering at Uber

3. Payments Experience • Rider • Driver • Cash • Platforms Developer Experience • Mobile • Backend Amsterdam HQ • ~100 tech (dev, design, DS, PM, UX) • ~700 total Engineering @ Uber Amsterdam

4. Payments Experience • Rider • Driver • Cash • Platforms Developer Experience • Mobile • Backend Engineering @ Uber Amsterdam

5. Motivation Architecture Scaling an architecture in practice

7. ● History ● Architecture growth ● Goals of the rewrite Motivation

8. Initial Team

9. Team Growth

10. Over 100 mobile engineers? Request a ride Fare split Cash Uber for Business Credit card rewards points Promotions Promotions Safety Over 10 ways to pay Scheduled rides Drive for Uber Uber Eats, Freight, Self-driving vehicles... Experimentation 80 countries, 600 cities Performance Cash Instant payments Maps & navigation uberPOOL Driver incentives App health Developer tools Networking Feed cards Driver experience Driver recognition Airport pickup Uber Family Beacon Campaigns Fraud EATS app Courier experience Shipper experience Restaurant experience

11. App Growth

12. App Growth

13. App Growth

14. Let’s just change everything

15. 1. History 2. Architecture growth 3. Goals of the rewrite Motivation

16. Architecture Growth LoggedIn Activity ProductSelection Controller Menu Controller Location Controller Custom View Custom View Sub Controller

17. Architecture Growth: State

18. Architecture Growth: State LoggedInState LoggedIn Activity ProductSelection Controller Menu Controller Location Controller Custom View Custom View Sub Controller

19. Architecture Growth: State ... ... LoggedInState LoggedIn Activity ProductSelection Controller Menu Controller Location Controller Custom View Custom View Sub Controller LoggedIn Activity

20. Architecture Growth: State ... ... LoggedInState LoggedIn Activity ProductSelection Controller Menu Controller Location Controller Custom View Custom View Sub Controller LoggedIn Activity LoggedIn Activity

21. ● Number of engineers ● Understanding how the app works ● Shared state ● Modifying the app Our Biggest Problems

22. Shared State class DriverIsOnTheirWayToaster { var isOnTripAndHasNotBeenNotified:Boolean = false fun onCreate(stateStream: TripStateStream) { stateStream .state() .subscribe({ (trip, driver) -> if (trip == TripState.ON_THEIR_WAY) { isOnTripAndHasNotBeenNotified = true showToast(driver!!.name) } else if (trip == TripState.ON_TRIP) { isOnTripAndHasNotBeenNotified = false } }) } }

23. class DriverIsOnTheirWayToaster { var isOnTripAndHasNotBeenNotified:Boolean = false fun onCreate(stateStream: TripStateStream) { stateStream .state() .subscribe({ (trip, driver) -> if (trip == TripState.ON_THEIR_WAY) { isOnTripAndHasNotBeenNotified = true showToast(driver!!.name) } else if (trip == TripState.ON_TRIP) { isOnTripAndHasNotBeenNotified = false } }) } }

24. class DriverIsOnTheirWayToaster { fun onCreate(driver: Driver) { showToast(driver.name) } }

25. Modifying the App ... ... LoggedInState LoggedIn Activity ProductSelection Controller Menu Controller Location Controller Custom View Custom View Sub Controller LoggedIn Activity ... LoggedIn Activity ...... ProductSelection Controller Location Controller Menu Controller

26. 1. History 2. Architecture growth 3. Goals of the rewrite Motivation

27. ● Constraints ○ Native development ○ Independent iOS & Android™ codebases ● Opportunities ○ Mobile Platform team ○ iOS & Android monorepos Constraints & Opportunities

28. ● Isolation & testability ● Developer productivity ● Support continued growth for years ● 99.99% reliability of core flows ● Monitoring as a first class citizen ● De-risk experimentation Rewrite Goals

29. Rewrite Goals Image by Tsahi Levent-Levi Android is a trademark of Google LLC.

30. Rewriting the Uber App January June August November Core architecture, framework & tooling Core flow Everything else

31. RIBs Architecture What We Built Application Framework Scoping Routing Business-logic driven Dependency management Open source Monitoring Components Code generation Reactive data flows Testability Experimentation Plugins Networking Storage Location services Analytics Logging UI components

33. ● Application state ● Dependency scopes ● Designing of RIBs Architecture

34. The state management problem

35. State Tree Root LoggedInLoggedOut Onboarding Menu Request Home ShortcutsFeedCard Location Editor OnTrip ...

36. State transitions RIBs Root LoggedOut Backend LoggedIn Login request Session response LoggedOut

37. State Tree State tree drives the views Root LoggedInLoggedOut Onboarding Menu Request Home ShortcutsFeedCard Location Editor OnTrip ...

38. Request Home LoggedOut State Tree State tree drives the views Root LoggedInLoggedOut Onboarding Menu Request Home ShortcutsFeedCard Location Editor OnTrip ...

39. ● Application state ● Dependency scopes ● Designing of RIBs Architecture

40. Dependency Scopes Application driven by business logic Root LoggedInLoggedOut Onboarding Menu Request Home ShortcutsFeedCard Location Editor OnTrip ... LoggedOut

41. Dependency Scopes Application driven by business logic Root LoggedInLoggedOut Onboarding Menu Request Home ShortcutsFeedCard Location Editor OnTrip ...

42. Dependency Scopes Application driven by business logic Root LoggedInLoggedOut Onboarding Menu Request Home ShortcutsFeedCard Location Editor OnTrip ...

43. ● Application state ● Dependency scopes ● Designing RIBs Architecture

44. ● MVC, MVP, MVI, MVVM ● VIPER, (B)VIPER Popular Mobile Architectures

45. MV* Model Controller View Model Presenter View Model ViewModel View Model Intent View Input Input Input Input MVC MVI MVP MVVM

46. VIPER Interactor Business logic Router Route between screens View(Controller) Layout & animation Presenter UI logic & respond to user inputs Entity

47. ● View tree drives the app hierarchy ● Business logic & view trees are tightly coupled ● Deep scope hierarchies supported only based on view nesting MVC, MVP, MVVM, MVI & VIPER

48. (B)VIPER Making VIPER components reusable Interactor Business logic Router Route between screens View(Controller) Layout & animation Presenter UI logic & respond to user inputs EntityModule Builder Creates VIPER classes

49. RIBs Interactor Business logic of the app (aka “the brain”) Router Routes between RIBs View(Controller) Layout & Animation Presenter (Optional) Translation Logic View model UI event Data model Business logic calls Routing calls Builder Creates RIB units

50. Router Interactor Builder RIBs Presenter View

51. Request Home LoggedOut State Tree State tree drives the views Root LoggedInLoggedOut Onboarding Menu Request Home ShortcutsFeedCard Location Editor OnTrip ...

52. Demo

53. Data flow with RIBs

54. RIBs Interactor Router View(Controller ) Presenter (Optional) Builder Interactor Router View(Controller)Presenter EntityModule Builder RIBs (B)VIPER

55. Data flow with RIBs ServiceModel Stream Pushes state onto Service callsData model Non-state modifying responses Logic calls The Internets Interactor Router View(Controller)Presenter UI event View model Push/pull Data model Routing calls

56. Viewless RIBs

57. Viewless RIBs ServiceModel Stream Pushes state onto Service callsData model Non-state modifying responses Logic calls The Internets Interactor Router View(Controller)Presenter UI event View model Push/pull Data model Routing calls Attach / detach child RIBs

58. Demo

59. Viewless RIBs - demo

61. ● Adopting a framework with a large team ● Why RIBs worked ● Summary Scaling an architecture in practice

62. Adopting a framework with a large team

63. ● Code generation ● Onboarding ● Enforcing (architecture) patterns Adopting a framework with a large team

64. Rails for architecture & code Code Generation Android (IntelliJ, Android Studio) iOS (XCode) Open sourced

65. Onboarding ● How long does it really take to learn? ● Documentation ● Tutorials ● Encourage contribution Open sourced

66. ● Lint rules Enforcing (architecture) patterns ● (Blocking) code reviews

67. Enforcing (architecture) patterns ● Process for change suggestions (RFC) ● Lint rules ● (Blocking) code reviews

68. ● Code generation ● Onboarding ● Enforcing (architecture) patterns Adopting a framework with a large team ● Have a clear owner

69. ● Adopting a framework at scale ● Why RIBs worked ● Summary Scaling an architecture in practice

70. ● 3 apps, more than 200 developers ● More than 600 RIBs, reused within & across apps ● Less than 300 lines of code / class for most RIBs ● All business logic well unit tested ● Open sourced How RIBs worked out

71. ● Long dependency injection chains ● Too much (boilerplate) code ● [iOS] RIBs incompatible with plain Views Feedback from engineers after a year’s usage

72. ● Does your app have lots of non-visual state? ● Do you have a (fast) growing iOS & Android app/team? ● Do you have the bandwidth to invest in a new architecture? Is RIBs for you?

73. ● Adopting a framework at scale ● Why RIBs worked ● Summary RIBs in practice

75. Gergely Orosz Engineering Manager, Uber Amsterdam @GergelyOrosz eng.uber.com Thank you uber.github.io

76. Proprietary and confidential © 2017 Uber Technologies, Inc. All rights reserved. No part of this document may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage or retrieval systems, without permission in writing from Uber. This document is intended only for the use of the individual or entity to whom it is addressed and contains information that is privileged, confidential or otherwise exempt from disclosure under applicable law. All recipients of this document are notified that the information contained herein includes proprietary and confidential information of Uber, and recipient may not make use of, disseminate, or in any way disclose this document or any of the enclosed information to any person other than employees of addressee to the extent necessary for consultations with authorized personnel of Uber.

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