#React Native Internals Autoinstrumentation

React Native exports its own Systrace API, which supports synchronous, asynchronous and counter events. While this API is mostly used for development of RN itself, it is still exposed for production apps, but does nothing (i.e., calls are no-ops).

Ottrelite can optionally define global variables that this Systrace API uses, effectively making these calls effective. For instance, if you launch the app, you will see a hierarchy of events related to require() invocations.

Tracing of React Native internals in Java / Kotlin code (Android-only) is enabled by default if you apply the Gradle plugin. To disable it, explicitly specify, which variants should be instrumented in your Gradle build script, as shown in the section "Activating tracing of Java/Kotlin RN internals (Android only)".

#Activating the Systrace API

To enable React Native's internal tracing, pass the reviveSystraceAPI: true option when installing Ottrelite. This activates the global variables that React Native's Systrace API depends on, making internal framework calls visible in your traces.

Ottrelite.install(yourBackendsOfChoice, {
  reviveSystraceAPI: true,
});

Once enabled, you'll automatically see traces for React Native's internal operations like module loading and other framework-level activities that are already instrumented in the React Native source code.

#Activating tracing of Java/Kotlin RN internals (Android only)

In your android/app/build.gradle file, ensure that you have applied the Ottrelite Gradle plugin:

apply plugin: "com.callstack.ottrelite"

By default, all build variants will be instrumented. To apply it only to selected variants, specify them as follows:

apply plugin: "com.callstack.ottrelite"

ottreliteTracing {
  rnInstrumentationVariants = ["debug", "profiling"]
}

#Seeing it in practice

On both iOS and Android, the revived Systrace API will cause JS internals that are instrumented in RN source code to be traced, such as the require()s for modules required first time in a run.

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