Android engineering for scale at SoundCloud

The SoundCloud app has been installed by tens of millions of users and our Android team has tripled in size over the last year.

We want to share the engineering practices that we’ve come to value as our team, user base and codebase has grown. The cornerstone of our Android architecture is RxJava. We’ll talk about how it fits into our codebase and show some examples of the problems we’ve used it to solve.

Transcript

5. Subtitle
6. Subtitle STRATEGY
7. Subtitle
12. Subtitle ├── com │ └── soundcloud │ ├── android │ │ ├── stream │ │ │ ├── StreamAdapter.java │ │ │ ├── StreamFragment.java │ │ │ ├── StreamModule.java │ │ │ ├── StreamOperations.java │ │ │ ├── StreamStorage.java │ │ │ └── StreamItemPresenter.java
14. if (flags.isEnabled(Feature.SECRET_PROJECT)) { return “Secret project”; } else { return “Nothing here”; }
15. <<new component>> branch <<old component>> master <<old component>> origin/master
16. master abstraction layer <<new component>> <<old component>>
17. master abstraction layer <<new component>>
18. master <<new component>>
19. master feature-B .isEnabled() .isEnabled() feature-A .isEnabled() feature-C
22. Subtitle public MainActivity() { SoundCloudApplication.getObjectGraph().inject(this); addLifeCycleComponent(playerController); addLifeCycleComponent(adPlayerController); presenter.attach(this); }
23. @Inject public PlayerController( EventBus eventBus, TrackPagerAdapter adapter, PlayerPresenter presenter, PlayQueueManager playQueueManager) { [...] }
26. BETA
27. Subtitle
28. iOS Android
29. API Mobile
30. Subtitle { "id":612849, "kind":"user", "permalink":"bazan", "username":"David Bazan", "uri":"https://api.soundcloud.com/users/612849", "permalink_url":"http://soundcloud.com/bazan", "avatar_url":"https://i1.sndcdn.com/avatars-000030728315- oe5uld-large.jpg?e76cf77", "country":"United States", "first_name":"David", "last_name":"Bazan", "full_name":"David Bazan", "description":"Known for his work fronting the enigmatic rock band Pedro the Lion, David Bazan\u2019s emotionally charged narratives, eye for telling detail, and mournful voice have more in common with J.D. Salinger\u2019s \u201cNine Stories\u201d or Flannery O\u2019Connor\u2019s \u201cWise Blood\u201d than with the usual lyrical slant of popular music. Bazan is a gifted storyteller, weaving parables of spiritual conflict, suburban ennui, and personal surrender into magnetic, well-crafted songs.\r\n\r\nHis debut solo full-length album, Curse Your Branches (out now on Barsuk), is a masterwork by a modern American poet at the height of his powers. Paste Magazine called him one of the \u201c100 Best Living Songwriters\u201d. This record is the deepest and most explicit exploration of his struggles with faith and a meditation on all things passed between the generations.", "city":"Seattle", "discogs_name":null, "myspace_name":"davidbazan", "website":"http://www.davidbazan.com", "website_title":"", "online":false, "track_count":32, { "collection":[ "hip hop", "chill", "electronic", "deep house", "party", "love", "rap", "happy", "study", "techno", "indie rock", "dubstep", "r&b", "relax", "country", "pop", "edm", "reggae", "house", "workout", "soundtrack", "reggaeton", "piano", "dance", "remix", "alternative", "summer", "instrumental", "rock", "morning", "funk", "classical", "punk", "electro", "trap", "club", "acoustic", "motivation", "jazz",
31. bazooka scale -r 934e08c -n 30 -e PROD
32. Subtitle
35. Subtitle @Provides PlayerController providePlayerController(Flags flags) { if (flags.isEnabled(Feature.VISUAL_PLAYER)) { return new SlidingPlayerController(); } else { return new LegacyPlayerController(); } }
36. Subtitle
37. ... ... ...
38. Reactive!
39. public final class EventQueue { public static final Queue<StateTransition> PLAYBACK_STATE; public static final Queue<ProgressEvent> PLAYBACK_PROGRESS; public static final Queue<PlayableEvent> PLAYABLE_CHANGED; [...] }
40. Subtitle eventBus.queue(EventQueue.PLAYABLE_CHANGE) .filter(PlayableEvent.IS_TRACK_FILTER) .doOnNext(invalidateUICache) .observeOn(AndroidSchedulers.mainThread())
41. Subtitle Observable.combineLatest( eventBus.queue(EventQueue.PLAY_QUEUE_TRACK), eventBus.queue(EventQueue.PLAYER_UI), combineStates) .doOnNext(setTrackHasBeenSeen)
42. Subtitle