6 lessons learned scaling mobile at SoundCloud

SoundCloud’s Android and iOS apps fast became our primary listening platforms. This talk will highlight the biggest things we’ve gotten right and wrong in the process. We’ll discuss how and when we’ve been able to share code, APIs and values. We also face many platform-specific challenges. We’ll compare and contrast some of the problems faced, patterns adopted and tools developed for one platform or the other.

Transcript

2. 6 lessons learned scaling mobile Jamie McDonald & Matej Balantič
3. 175M+ monthly unique listeners ~20 mobile engineers
4. 1 Product over platform
5. SoundCloud Pulse
6. Aligned experience
8. 2 Find opportunities to share
9. BFFs
10. Android iOS Mobile API Skippy Skippy Through the stack
11. More • Values • Practices • Knowledge
12. 3 Confront technical debt
13. Brand new app Alternate approaches Modernise by vertical
14. Android • Legacy code • Small, incremental improvements • Re-build vertical slices
15. Successive, well intentioned, changes to architecture throughout the lifetime of a project can lead to a fragmented and hard-to-maintain code base Lava layers
16. Rewrite by abstraction
17. Rewrite by abstraction
19. • Legacy project by an external agency • Decision to start from scratch • Big bang release* * except iPad which got delayed iOS
21. • Fresh start with code architecture • Away with legacy code once and for all • Innovation on hold for a while • Might need to sacrifice existing features → angry users Rewrite aftermath
22. Positive side effect User complaints about iOS app crashes
23. 4 Avoid premature reorganisation
24. The challenge Scaling the team
25. How we thought we’ll solve it Scaling the team
26. How it was in practice Scaling the team
27. Expectations Path to feature teams
28. Reality Path to feature teams
29. Current transitional structure Scaling the team
30. 5 Empower teams
31. iOS/Android team Search Stations Sign-in Creators ... Traditional release model
32. Search Stations Sign-in Creators ... Relase train model
33. Empower teams • Everyone can ship to master* • Put the code behind a feature flag • Enable the feature once ready to ship * Pairing required. When working alone you need 2x on your pull request.
34. Release train Feature development & QA Review / Public Beta Feature freeze Feature freeze Feature freeze
35. Build time configuration "release": { "inherits_from": "adhoc", "dev_always_skippy": { "enabled": false } } "release": { "inherits_from": "adhoc", "dev_always_skippy": { "enabled": true } }
36. Run time configuration
37. Behind the feature flag - (void)registerAppShortcuts { if ([FTSFlipTheSwitch isDevAppShortcutsEnabled]) { [self registerInitialActions]; } }
38. “You break it, you buy fix it” • Continuous integration allows us to trust that we’re not breaking features • Good unit and acceptance tests as an insurance policy
39. 6 Invest in solid patterns and tools
40. Android • Reactive programming (RxJava) • Release pipeline • Architecture & testability
41. LightCycle @Inject @LightCycle ActionBarUtil actionBarUtil; @Inject @LightCycle PlayerController playerController; public MainActivity() { [...] }
42. iOS • Reactive programming (ReactiveCoca) • Stable CoreData stack • Dependency inversion
44. Thank you, London! soundcloud.com/jobs Jamie McDonald -- @jdamcd Matej Balantič -- @skavt
45. Mobile BFF: https://www.thoughtworks.com/insights/blog/bff-soundcloud Lava layer anti-pattern: http://mikehadlow.blogspot.de/2014/12/the-lava-layer-anti-pattern.html Branch by abstraction: http://martinfowler.com/bliki/BranchByAbstraction.html Command pattern: https://sourcemaking.com/design_patterns/command Android architecture: https://realm.io/news/gotocph-mattias-kappler-reactive-architecture-android Mobile CI @ SoundCloud: https://www.youtube.com/watch?v=Rq721qtKKNk Dependency Inversion Principle: http://martinfowler.com/articles/dipInTheWild.html References