Feature Flag Best Practices - A case study of LINE Android

Hidetsugu Tamaki
LINE App Dev Team3 Software Engineer
https://linedevday.linecorp.com/2020/ja/sessions/3506
https://linedevday.linecorp.com/2020/en/sessions/3506

Transcript

2. Introduction > LINE Android development Hidetsugu Tamaki > Apr. 2018 ~ > Software Engineer
3. Agenda › What is Feature Flag-based development? › Best Practice 1: Change logic with Feature Flag › Best Practice 2: Guard the only entry point
4. Agenda › What is Feature Flag-based development? › Best Practice 1: Change logic with Feature Flag › Best Practice 2: Guard the only entry point
5. Feature Branch Strategy Main branch Sticker feature branch Pull requests
6. Feature Flag Strategy Main branch Sticker feature PRs
7. Feature Flag Strategy Main branch Sticker feature PRs val FEATURE_STICKER = false
8. Feature Flag Strategy Main branch Sticker feature PRs val FEATURE_STICKER = false true
9. Feature Flag Achieves > Instant toggling > Smoother release schedule management > Conflict minimization > Better collaboration with stakeholders
10. Feature Flag Achieves > Instant toggling > Smoother release schedule management > Conflict minimization > Better collaboration with stakeholders
11. References https://youtu.be/tQ56xi-j88s Presented at LINE DEV DAY 2019 https://speakerdeck.com/line_devday2019/journey-of-feature-flag-development-in-line-android https://youtu.be/H81EEAZ4XAI Presented at DroidKaigi 2019 https://speakerdeck.com/line_developers/flag-based-feature-management
12. Agenda › What is Feature Flag-based development? › Best Practice 1: Change logic with Feature Flag › Best Practice 2: Guard the only entry point
13. Case Study: Refactoring Complex Logic Local Storage
14. Case Study: Refactoring Complex Logic Logics Local Storage
15. Structure of Image File Managers > Scattered logics UseCase ImageFilePathUtil StorageUtil ImageUtil Depends on ImageFileManager BaseFileManager
16. BaseFileManager Structure of Image File Managers > Scattered logics UseCase ImageFilePathUtil StorageUtil ImageUtil ImageFileManager Depends on OldFileManager
17. Structure of Image File Managers > New logics applied one by one UseCase NewFileManager ✗ ✗ ✗ OldFileManager
18. ✗ ✗ ✗ NewFileManager OldFileManager Structure of Image File Managers > New logics applied one by one UseCase No Feature Flag to toggle
19. Problem: Hard to Revert > Critical if many bugs reported Main branch Problematic PR Dependency Revert Conflict ! Another PR
20. Best Practice: Change Logic with Feature Flag UseCase OldFileManager NewFileManager val FEATURE_REFACTORING = true Change Reference val FEATURE_REFACTORING = false
21. Agenda › What is Feature Flag-based development? › Best Practice 1: Change Logic with Feature Flag › Best Practice 2: Guard the only entry point
22. Case Study: New Recommendation Feature
23. Case Study: New Recommendation Feature WorkManager Enqueue Query Server
24. Case Study: New Recommendation Feature Local Storage WorkManager Cache Enqueue Query Server
25. Case Study: New Recommendation Feature Local Storage WorkManager Cache Display Enqueue Query Server
26. Case Study: New Recommendation Feature Local Storage WorkManager Cache Display Enqueue Query Server
27. Best Practice: Guard the Only Entry Point Enqueue ✗ val FEATURE_RECOMMENDATION = false
28. Code Using Feature Flag // Application initialization function fun onCreate() { // The other initialization codes if (FeatureFlag.HOME_TAB_RECOMMENDATION) { val periodicSyncRequest: WorkRequest = … WorkManager.getInstance(…).enqueue(periodicSyncRequest) } }
29. Case Study: Replace Message ListView MessageListActivity MessageListViewAdapter ListView API
30. Case Study: Replace Message ListView MessageListActivity MessageListViewAdapter ListView API
31. MessageListViewAdapter Case Study: Replace Message ListView MessageListActivity ListView API ListView API
32. MessageListViewAdapter Case Study: Replace Message ListView MessageListActivity ListView API MessageListAdapterInterface
33. MessageListViewAdapter Case Study: Replace Message ListView MessageListActivity MessageListAdapterInterface
34. MessageListViewAdapter Case Study: Replace Message ListView MessageListActivity MessageListAdapterInterface MessageRecyclerViewAdapter
35. MessageListViewAdapter Best Practice: Guard the Only Entry Point MessageListActivity MessageListAdapterInterface MessageRecyclerViewAdapter val RECYCLER_VIEW_REPLACEMENT = false val RECYCLER_VIEW_REPLACEMENT = true Change Implementation
36. Code Using Feature Flag val adapter = if (FeatureFlag.RECYCLER_VIEW_REPLACEMENT) { MessageRecyclerViewAdapter(…) } else { MessageListViewAdapter(…) } setAdapter(adapter)
37. > Minimize reverting cost with instant toggling Summary > Find a single entry point for easiest application
38. Thank you