[G1-Sync] Manual knowledge update

2026-05-09 21:08:02 +09:00
parent f0befc887a
commit 93ec7e9056
363 changed files with 68333 additions and 64 deletions
@@ -0,0 +1,178 @@
+---
+id: mobile-crash-free-slo
+title: Crash-free SLO — 99.5% 유지하기
+category: Coding
+status: draft
+source_trust_level: B
+verification_status: conceptual
+created_at: 2026-05-09
+updated_at: 2026-05-09
+tags: [mobile, crash, slo, reliability, vibe-coding]
+tech_stack: { language: "Swift / Kotlin / RN", applicable_to: ["iOS", "Android"] }
+applied_in: []
+aliases: [crash-free, crashlytics SLO, ANR rate, mean time to detect, MTTD]
+---
+
+# Crash-free SLO
+
+> Crash-free users 99.5%+ 가 산업 표준. **측정 + 알람 + 빠른 hotfix 채널**. iOS / Android 별 다름. **Crashlytics velocity alert** 자동.
+
+## 📖 핵심 개념
+- Crash-free users: 24h 동안 crash 안 본 사용자 비율.
+- Crash-free sessions: 한 세션 안 crash 없음 비율.
+- Velocity: 짧은 시간 내 빠른 증가 = 즉각 알람.
+- ANR rate (Android): 별도 SLO.
+
+## 💻 코드 패턴
+
+### Crashlytics velocity alert
+```
+Firebase Console → Crashlytics → Velocity Alerts
+- Threshold: 1% sessions affected
+- Window: 1 hour
+- Slack / email integration
+```
+
+### Sentry release health
+```ts
+// 앱 시작 시
+Sentry.init({
+  dsn,
+  release: `app@${version}+${build}`,
+  environment: 'prod',
+  tracesSampleRate: 0.1,
+  enableAutoSessionTracking: true,
+});
+```
+
+```
+Sentry Dashboard → Releases → Crash-free users / sessions
+```
+
+### SLO 정의
+```yaml
+SLO:
+  crash_free_users_30d: 99.5%
+  crash_free_sessions_30d: 99.8%
+  ANR_rate_24h: < 0.47% (Play Console 표준)
+  startup_latency_p95: < 2s
+
+Alerts:
+  - velocity > 1% in 1h → page oncall
+  - daily crash-free < 99% → page
+  - new crash signature affecting > 50 users / 1h → page
+```
+
+### 디버그 정보
+```ts
+Crashlytics.crashlytics().setUserID(user.id);
+Crashlytics.crashlytics().setCustomValue(plan, forKey: 'plan');
+Crashlytics.crashlytics().setCustomValue(experimentVariant, forKey: 'exp:onboarding');
+Crashlytics.crashlytics().log("entered checkout flow")
+```
+
+### Symbol 업로드 자동
+```
+Fastlane: upload_symbols_to_crashlytics
+또는 build script
+```
+
+dSYM 누락 = crash 의미 없음.
+
+### Hotfix 채널
+- iOS: TestFlight + 빠른 review (24h) + phased release pause.
+- Android: Play Console internal testing → staged rollout 5% → full.
+
+```ruby
+# Fastlane: emergency hotfix 자동
+lane :hotfix do
+  ensure_git_branch(branch: 'hotfix/.*')
+  match
+  build_app
+  upload_to_testflight(distribute_external: true, groups: ['Beta'])
+end
+```
+
+### Phased release / staged rollout
+```ruby
+# iOS: App Store Connect API
+upload_to_app_store(
+  phased_release: true,  # 7일 자동 분배
+)
+
+# Android
+upload_to_play_store(track: 'production', rollout: '0.05')
+```
+
+새 버전 issue 발견 → halt rollout.
+
+### Kill switch (서버 제어 강제)
+```ts
+// 앱 시작 시 remote config
+const config = await fetchRemoteConfig();
+if (config.minSupportedBuild > currentBuild) {
+  showUpdateRequiredScreen();
+  return;
+}
+if (config.killFeature.checkout) {
+  // checkout 비활성
+}
+```
+
+### Client error rate (non-crash)
+```ts
+class GlobalErrorBoundary extends React.Component {
+  componentDidCatch(error: Error, info: ErrorInfo) {
+    Sentry.captureException(error, { extra: info });
+    this.setState({ hasError: true });
+  }
+}
+```
+
+```ts
+// JS unhandled rejection
+window.addEventListener('unhandledrejection', (e) => {
+  Sentry.captureException(e.reason);
+});
+```
+
+### Postmortem 템플릿
+```markdown
+# Crash spike 2026-05-09
+- Affected: 23,000 users (3.4%)
+- Window: 14:00 - 15:30 UTC
+- Root cause: 새 endpoint 의 nil response → force unwrap
+- Fix: optional unwrap + fallback
+- Hotfix: 1.4.2 (3 hours)
+- Prevention: 빌드 시 force-unwrap lint 활성, integration test 추가
+```
+
+## 🤔 의사결정 기준
+| 모니터 | 도구 |
+|---|---|
+| 일반 SLO | Crashlytics + Sentry |
+| ANR (Android) | Crashlytics + Play Console |
+| 시작 latency | Firebase Performance / SwiftUI Instruments |
+| 메모리 / 배터리 | MetricKit (iOS) / Battery Historian (Android) |
+| 네트워크 에러 | 자체 + Sentry breadcrumbs |
+| User journey crash 영향 | Mixpanel / Amplitude |
+
+## ❌ 안티패턴
+- **dSYM / mapping 누락**: stack 의미 없음.
+- **Crash velocity 알람 없음**: 큰 spike 모름.
+- **Force unwrap (`!`) 무절제 (Swift)**: nil 시 crash. 옵션 unwrap.
+- **Catch 후 swallow + continue**: 더 큰 crash. 또는 record + degrade.
+- **Phased release 없음 prod**: 큰 영향 즉시.
+- **Kill switch 없음**: emergency 시 review 기다림.
+- **PII crash log 그대로**: GDPR. 마스킹.
+- **Old version 무한 지원**: minSupportedBuild + 강제 update.
+
+## 🤖 LLM 활용 힌트
+- Crashlytics + Sentry 양쪽 권장 (각 강점 다름).
+- Velocity alert + dSYM 자동 + phased release.
+- Kill switch 로 emergency 대응.
+
+## 🔗 관련 문서
+- [[Native_Crash_Reporting]]
+- [[Mobile_CI_CD_Fastlane]]
+- [[Native_ANR_Freeze_Debugging]]