Chrome unable to load the transformed profile: Failed to find browser main thread in trace, some timeline features may be unavailable

[ofreyssinet-ledger]

EDIT:
one workaround is to use chrome://tracing to inspect profile

---

Hello, I'm trying to profile a react-native app, I followed the official documentation on how to pull and transform the Hermes tracing profile.

So once the profile is recorded I'm running this:

npx react-native profile-hermes \
  --sourcemap-path './android/app/build/intermediates/sourcemaps/react/debug/index.android.bundle.packager.map'\
  ~/Downloads

It outputs this:

warn Package expo-modules-core has been ignored because it contains invalid configuration. Reason: "dependency.platforms.ios" must be of type object
info Downloading a Hermes Sampling Profiler from your Android device...
info No filename is provided, pulling latest file
info File to be pulled: sampling-profiler-trace1250977739574747452.cpuprofile
success Successfully converted to Chrome tracing format and pulled the file to /Users/olivier.freyssinet/Downloads/sampling-profiler-trace1250977739574747452-converted.json

And here attached you can file the output .json. I don't know about the formatting but it seems to contain actual data that reflects what's going on in my app, so then it's just a matter of parsing it I guess.

So then I try to load it in the performance tab of Chrome Version 109.0.5414.119 (Official Build) (arm64)
It seems to be parsing the whole file but then nothing is displayed and I get the following error in the console (three times):

17:30:02.957 Failed to find browser main thread in trace, some timeline features may be unavailable
17:30:02.958 Failed to find browser main thread in trace, some timeline features may be unavailable
17:30:02.982 Failed to find browser main thread in trace, some timeline features may be unavailable

Another person who is trying on a Linux computer gets this slightly more explicit error:

Error parsing trace data: no TracingStartedInBrowser event found

Screen.Recording.2023-01-31.at.17.40.50.mov

---

Hermes version:

"hermes-engine": "0.11.0"

react-native info output

System:
    OS: macOS 12.5.1
    CPU: (10) arm64 Apple M1 Max
    Memory: 96.39 MB / 32.00 GB
    Shell: 5.8.1 - /bin/zsh
  Binaries:
    Node: 16.15.0 - /usr/local/bin/node
    Yarn: 1.22.18 - /opt/homebrew/bin/yarn
    npm: 8.5.5 - /usr/local/bin/npm
    Watchman: 2022.09.19.00 - /opt/homebrew/bin/watchman
  Managers:
    CocoaPods: 1.11.3 - /usr/local/bin/pod
  SDKs:
    iOS SDK:
      Platforms: DriverKit 22.2, iOS 16.2, macOS 13.1, tvOS 16.1, watchOS 9.1
    Android SDK:
      API Levels: 29, 30, 31, 32, 33
      Build Tools: 28.0.3, 30.0.2, 30.0.3, 31.0.0, 32.0.0, 32.1.0
      System Images: android-31 | Google APIs ARM 64 v8a, android-32 | Google APIs ARM 64 v8a, chromeos-67 | Chrome OS 67
      Android NDK: 22.1.7171670
  IDEs:
    Android Studio: 2021.1 AI-211.7628.21.2111.8309675
    Xcode: 14.2/14C18 - /usr/bin/xcodebuild
  Languages:
    Java: 11.0.15 - /usr/bin/javac
  npmPackages:
    @react-native-community/cli: ^7.0.1 => 7.0.4 
    react: ^17.0.2 => 17.0.2 
    react-native: 0.68.5 => 0.68.5 
    react-native-macos: Not Found
  npmGlobalPackages:
    *react-native*: Not Found

Thanks in advance for any help! 🙏

[fmorau]

@ofreyssinet-ledger did you find an issue?

[ofreyssinet-ledger]

@chelovekdrakon I use chrome://tracing and it works fine on that tool