Engineering joy: Building the celebration system on the Home tab of the LINE app on Android

LINEのホームタブでの祝祭アニメーションの技術アーキテクチャを深く掘り下げ、Androidの核となる構成要素がいかにして日常の瞬間を大規模な魔法の祝祭に変えるかを探ります。

Transcript

1. Engineering Joy: Building LINE's Android Celebration System at Scale LY Corporation, LINE App Dev Tuan (Tuna)
2. - Android Software Engineer - Working on LINE's Home tab features - Passionate about building delightful user experiences About me
3. 1. Showcase 2. The Challenge 3. System Architecture Overview 4. Implementation Deep Dive 5. Building Blocks Synergy 6. Results & Impact 7. Questions & Discussion Agenda
4. Birthday & Christmas Celebrations LINE App Home tab during
5. The Challenge - Precision Timing Events must trigger exactly when intended, surviving app restarts - Resource Management Efficient handling of celebration assets across millions of devices - Edge Cases Network failures, app terminations, multiple concurrent celebrations
6. Our Solution Reliable Magic 3 Building Blocks 4-Phase Architecture = +
7. System Architecture Overview
8. 3 Building Blocks Foundation - Room Database: Reliable local storage with reactive queries - WorkManager: Precise scheduling across app lifecycle - Kotlin Flow: Reactive UI updates and state management
9. 4-Phase Journey Event Discovery Resource Acquisition Show Time Clean Up Receive event notification Download event metadata Download and validate resources Display effects at the designated time Clean up resources Schedule next occurrence Maintain readiness during idle periods
10. Key Design Principles - 5-day preparation buffer ensures reliable delivery - Clear separation of concerns between phases - Independent error handling in each component - User-centric timing with grace periods
11. Implementation Deep Dive Journey Through All Four Phases
12. Phase 1: Event Discovery Client side Server pushed scheduledTime = showTime - 5 days retryUntil = showTime + 1 day WorkManager {showTime} Worker {showTime}
13. Phase 2: Resource Acquisition Metadata Fetching Asset Download retry retry Done
14. Robust Implementation // Metadata Worker: Fetch event configurations if (retryUntil < now) { return failure() } val event = fetchEventMetadata(eventId) // error -> retry saveEventMetadata(event) // error -> retry scheduleAssetDownload(event) // success -> next step Metadata Worker: Fetch event configurations
15. Robust Implementation // Asset Worker: Download and validate celebration assets if (retryUntil < now) { return failure() } val asset = downloadAsset(event) // error -> retry validateAsset(asset, event.checksum) // error -> retry fileStorage.extractAndSave(eventId, asset) // error -> retry // success scheduleShowtime() && scheduleCleanup() Asset Worker: Download and validate celebration assets
16. Phase 2: Resource Acquisition Metadata Fetching Asset Download retry retry Done Scheduling Show time Scheduling Clean up WorkManager RoomDB
17. Phase 3: Show Time PENDING READY FULL_SCREEN_ EFFECT_COMPLETED All Building Blocks Unite
18. Elegant Simplicity // WorkManager: One simple state change eventRepository.updateEventState(eventId, READY) // Everything else happens automatically: // Room → Flow → UI updates seamlessly
19. Perfect Collaboration - WorkManager: Triggers the precise moment with one line of code - Room: Reactive database instantly notifies all observers - Flow: Handles complex priority, timing, and UI coordination automatically
20. Phase 4: Clean Up - 1-day grace period prevents interruption for late users - Comprehensive removal of assets and metadata - Recurring events automatically reschedule next occurrence Efficient Resource Management
21. Phase map Phase 1 Phase 2 retry Phase 3 Phase 4
22. Building Blocks Synergy Complex State Management Made Simple
23. The Power of Integration WorkManager schedules Room stores / queries Flow reacts UI updates
24. Real Impact: Complex Logic in Simple Code // All three building blocks working together: val displayableEventFlow = combine( homeEventEffectDao.getDisplayableEventsFlow(), // Room: reactive queries homeTabVisibilityFlow // Flow: UI state tracking ) { events, isHomeVisible -> events.takeIf { isHomeVisible } // Timing: only when visible ?.maxByOrNull { it.priority } // Priority: personal > cultural } // WorkManager updates Room → Room triggers Flow → Flow updates UI displayableEventFlow.collect { event -> showEffect(event) }
25. What This Achieves - Complex coordination becomes declarative programming - Multi-phase state transitions handled automatically - Error recovery across 4 phases with single retry strategy - Reactive UI updates eliminate manual state synchronization Result: Complex celebration orchestration → Simple reactive declarations
26. Results & Impact
27. Performance Achievements celebration delivery Success rate 99.9% impact App startup Zero during idle periods Resources footprint Low
28. Automatic recovery from network failures and app crashes or restarts Technical Excellence of building blocks for complex state management Seamless integration simplifies quality assurance Independent phase testing
29. Perfect timing creates genuine surprise moments User Experience ensures birthdays aren't missed by holidays Personal priority enhance emotional impact Cultural awareness enhance emotional impact Smooth animations
30. Key Takeaways
31. Architecture Lessons - Strategic preparation (5-day buffer) prevents last-minute failures - Phase isolation enables independent error handling and testing - Building block synergy leverages Android's strengths effectively - User-centric design transforms technical constraints into delightful experiences
32. Implementation Insights - Early resource acquisition ensures reliable celebration delivery - Reactive state management through Flow simplifies complex UI coordination - WorkManager scheduling coordinates precise phase transitions and retry logic - Room's reactive queries provide real-time system state awareness
33. Thank You
34. - Engineering joy: Building the celebration system on the Home tab of the LINE app on Android https://techblog.lycorp.co.jp/en/engineering-joy-building-the-celebration-system-on-the-home-tab-of-the-line- app-on-android - Kotlin Flow Documentation https://kotlinlang.org/docs/flow.html - Room Database Documentation https://developer.android.com/training/data-storage/room - WorkManager Documentation https://developer.android.com/topic/libraries/architecture/workmanager References