Reproduction for sentry-react-native#5561

[antonis]

Reproduction for sentry-react-native#5561

Issue: getsentry/sentry-react-native#5561

Summary

This reproduction successfully demonstrates the excessive getRandomValues calls issue reported in sentry-react-native#5561. The app shows that a single HTTP request triggers 62-93 calls to getRandomValues instead of the expected 2-5 calls.

Key Findings

✅ Issue Reproduced: 62-93 getRandomValues calls per fetch request
✅ Root Cause Identified: Only 1 unique call pattern executed 62 times (61 duplicates)
✅ Location: @sentry/core tracing utilities

Root Cause Analysis

The investigation revealed that all 62 calls share the same stack trace, indicating the same code path is being executed repeatedly. The calls originate from:

1. generateSentryTraceHeader() / generateTraceparentHeader() in @sentry/core/build/esm/utils/tracing.js
2. These functions use default parameters traceId = generateTraceId() and spanId = generateSpanId()
3. Functions are being called without passing ID values, triggering UUID generation each time
4. Each UUID generation calls getRandomByte() via String.replace() callback

How to Run

See the README for detailed setup instructions.

cd sentry-react-native/5561
npm install
npx @react-native-community/cli init SentryReproApp --directory . --skip-install
cd ios && pod install && cd ..
npm run ios

The app includes instrumentation that displays:

• Real-time counter of getRandomValues calls
• Analysis showing unique vs duplicated call patterns
• Detailed console logs with stack traces

Environment

• React Native: 0.81.5
• @sentry/react-native: 7.2.0
• Tested on: iOS Simulator (iPhone 16 Pro)

🤖 Generated with Claude Code

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Unused variable data from response parsing

Low Severity

The data variable is assigned from response.json() but never used anywhere in the code. This dead store adds unnecessary code and could confuse future maintainers about whether the parsed response data is needed. If the JSON parsing is intentional to simulate a complete request lifecycle, the result can be discarded without assignment, or the parsing can be removed entirely.

 

[antonis]

Closing this repro as it served its purpose