React Native Android Startup - logging

MainApplication.java

@Override
public void onCreate() {
  super.onCreate();
  
  ///////// Add lines below this to capture times of the large sections
  final String TAG = "RN_STARTUP"; // If you already have a TAG for the app, use that instead. 
  final TimingLogger timingLogger = new TimingLogger("AXE", "REACT_NATIVE_STARTUP");
  timingLogger.reset();
  ReactMarker.addListener(new ReactMarker.MarkerListener() {
      @Override
      public void logMarker(ReactMarkerConstants constant, @Nullable String tag, int instanceKey) {
          StringBuilder message = new StringBuilder(constant.toString()).append(" ").append(tag).append(" ").append(instanceKey);
          // While we log these in ADB logcat, you should ideally also log these from production. 
          // That way, you will more accurate timings from real devices. You can cross reference this with device types too !
          // Basically, just save the timestamps to a list, and then upload the times to your server in the next method. 
        
          //Also note that the markers have a _START and an _END, so you could even log timespans, instead of just timestamps
          Log.i("REACT_NATIVE_STARTUP", message.toString());
          timingLogger.addSplit(message.toString());
      }
  });
  
  // This should not be just a simple handler, but should be invoked after your "Load" event. The "Load" event itself is 
  // different for different apps - some define it as the time a first screen is displayed, for others, it is defined as when 
  // a network request returns with data and all of that is rendered. 
  
  // For now, we can live with a 10second delay, will talk more about the actual end of a "Load" event in a subsequent post. 
  new Handler().postDelayed(new Runnable() {
      @Override
      public void run() {
         // During development, you will see this in ADB logcat. Just ensure that you run 
         // adb shell setprop log.tag.RN_STARTUP VERBOSE on the terminal, before running adb logcat
        
         // This is where you would upload all the timespans to a server, so that you can aggregate them
         timingLogger.dumpToLog();
      }
  }, 10000);
  /////////////////// End of snippet
  

  SoLoader.init(this, /* native exopackage */ false);

}

Have questions about this script ? Leave your questions here, and will try to answer them

Add this script to RNTester ?

@gengjiawen - sure, but where will be log the data ?

Ram, I had been using this technique but face one issue - When I use multiple react instances in my app, how do I know which measure is of which instance? One very crude way is maybe make some rough sense from thread ids. Also what if multiple React instances(context + bridge init) are happening simultaneously in the same app