This is a small project that should help reproducing an (Android) React Native DataDog bug, resulting in all timings/actions to be off after locking the screen while the app is in the foreground.

Getting started:

Please follow these steps to get the reproduction app running on your device.

1. Install dependencies:

yarn install

2. Create a release bundle:

yarn react-native bundle --platform android --dev false --entry-file index.js --bundle-output android/app/src/main/assets/index.android.bundle --assets-dest android/app/src/main/res/

3. Create a release APK:

cd android && ./gradlew assembleRelease

4. Install APK:

adb install app/build/outputs/apk/release/app-release.apk

Reproduction steps:

1. Run project on a device (not on an emulator)
2. Disconnect any cables from the device (otherwise the device won't sleep ⚠️)
3. Lock device while app is in the foreground
4. Wait 10 minutes
5. Connect the device with your computer again
6. Unlock device
7. Inspect ADB logs containing DEBUG_TIME

After following these steps, you can compare the different logs. It's important to compare the actual time of the ADB log entry with the now() timestamp (the TimeProvider timestamp) in the log payload.

While now() seems to match the ADB log time when initially opening the app, it's not longer correct after the device was locked for some time.

Example logs:

# The initial log
2024-05-24 09:52:00.183 23224-23255 ReactNativeJS           com.datadogtry                       I  'DEBUG_TIME', { baseOffset: 1716534807180.3003,
                                                                                                      'Date.now()': 1716537120182,
                                                                                                      'performance.now()': 2313001.884388,
                                                                                                      'now()': 1716537120182.197 }
# The second log, emitted after the phone was locked for some time
2024-05-24 10:09:23.828 23224-23255 ReactNativeJS           com.datadogtry                       I  'DEBUG_TIME', { baseOffset: 1716534807180.3003,
                                                                                                      'Date.now()': 1716538163828,
                                                                                                      'performance.now()': 2431997.942877,
                                                                                                      'now()': 1716537239178.248 }

Analysis

The first ADB log was emitted at 2024-05-24 09:52:00.183, which matches the now() of 1716537120182.197 (Friday, 24 May 2024 09:52:00.182)

However, the second ADB log was emitted at 2024-05-24 10:09:23.828, while that now() is 1716537239178.248 (Friday, 24 May 2024 09:53:59).

As you can see, the second timestamp has an offset of ~15 minutes ⚠️ As a result, any follow-up DataDog actions or timings will be inserted wrongly into the timeline.

Possible root cause

While debugging, we noticed that the result of React Native's performance.now() seems to be incorrect on Android after locking the device for some time while the app is in the foreground.

It might be worth to investigate if the issue is reproducable when using react-native-performance instead. According to the author, Facebook's implementation of the Performance API is not very reliable.