observability-and-instrumentation

Observability and Instrumentation

Overview

You cannot fix what you cannot see. This skill makes production behavior observable: crashes and ANRs reported with enough context to fix, startup and jank measured against Play Vitals thresholds, and logs structured so they help without leaking user data. Instrumentation is part of the feature, not an afterthought bolted on when the first bad review arrives.

When to Use

• Adding a feature whose failures would be invisible without instrumentation (payments, sync, background work)
• Setting up or auditing crash reporting and performance monitoring
• Before any release that will be watched during staged rollout (see shipping-and-launch)
• Investigating field-only issues where local reproduction failed (see debugging-and-error-recovery)

Skip when: Prototypes or internal builds that will never reach users — but wire observability in before the first external release, not after.

Core Process

Step 1: Crash and ANR Reporting

1. Crashlytics (or Sentry) with context, not just stack traces:

// Attach the state that turns a stack trace into a diagnosis
FirebaseCrashlytics.getInstance().apply {
    setCustomKey("screen", "task_detail")
    setCustomKey("sync_state", syncState.name)
    setUserId(pseudonymousId)          // NEVER an email or real identifier
    recordException(NonFatalSyncError(cause))  // non-fatals for handled-but-wrong paths
}

1. Reporting rules:
   • Record non-fatal exceptions for caught-but-abnormal paths — a swallowed exception is an invisible bug
   • Custom keys over log spam: state at crash time beats a breadcrumb trail
   • Upload the R8 mapping file automatically in the release pipeline (Crashlytics Gradle plugin does this) — an obfuscated stack trace is noise
   • ANRs are surfaced by Play Vitals, not your crash SDK — watch both

Step 2: Play Vitals Thresholds

1. Know the numbers Google judges you by (Play Console → Android Vitals):

Metric	Bad-behavior threshold
User-perceived ANR rate	0.47%
User-perceived crash rate	1.09%
Excessive wakeups / stuck wake locks	per-device-hour budgets