JLPluginOpenTelemetry

A Jasonelle plugin that wraps the OpenTelemetry SDK to track application metrics.

Overview

JLPluginOpenTelemetry bridges the OpenTelemetry Java SDK to JavaScript. It records counters and histograms on any meter, so metrics raised in the web view reach whatever exporter the app has configured.

Structure

File Role

Plugin.kt

Native side – connects to GlobalOpenTelemetry and records the requested metric.

Plugin.js

JavaScript side – registers the plugin on window.jasonelle.plugins.opentelemetry.

How it works

  1. The plugin is injected into the web view on page load and registers itself on window.jasonelle.plugins.opentelemetry.

  2. counter(name, value, meterName) and histogram(name, value, meterName) post a message to native and return a promise.

  3. The call is routed to Plugin.kt handle_call(callbackId:args:respond:), which reads action and dispatches to the requested metric action.

  4. The plugin builds the instrument on the requested meter, records the value, and resolves the promise.

await window.jasonelle.plugins.opentelemetry.counter("button_clicks", 1);
await window.jasonelle.plugins.opentelemetry.histogram("load_time_ms", 124.5);

The same call can be made without the JavaScript wrapper, using window.jasonelle.post to send the arguments straight to handle_call. The first argument is the plugin id, not the short name used to register it on window.jasonelle.plugins:

await window.jasonelle.post("com.jasonelle.plugins.opentelemetry", {
    action: "counter.add",
    name: "button_clicks",
    value: 1,
    meterName: "jasonelle.app.meter"
});

Arguments

Key Type Required Default Description

action

string

yes

–

counter.add or histogram.record.

name

string

yes

–

Instrument name, for example button_clicks.

value

number

yes

–

Value added to the counter, or recorded in the histogram.

meterName

string

no

jasonelle.app.meter

Meter the instrument is created on.

counter.add truncates value to a whole number, matching the LongCounter instrument on other platforms.

Response

{
  "status": "ok",
  "callbackId": "call_1",
  "success": true
}

success reports that the bridge call was accepted, not that a value reached the SDK. A missing or non-numeric name or value is dropped natively and the promise still resolves with success: true.

Errors

{
  "status": "error",
  "callbackId": "call_1",
  "error": "No action provided"
}

  • No action provided – the arguments carried no string action.

  • Unknown action <action> – action was neither counter.add nor histogram.record.

SDK requirement

The app must register an OpenTelemetry SDK before the first call. Without one GlobalOpenTelemetry.get() returns a no-op OpenTelemetry, every value is discarded and the promise still resolves with success: true. 
GlobalOpenTelemetry.set(
  OpenTelemetrySdk.builder()
    .setMeterProvider(
      SdkMeterProvider.builder()
        .setResource(Resource.getDefault().merge(Resource.create(Attributes.of(...))))
        .registerMetricReader(PeriodicMetricReader.create(exporter))
        .build()
    )
    .build()
)

Register the SDK in the Application module, before the web view loads the page that raises the first metric.

Reference

  • com.jasonelle.kernel.Plugin – the base class this plugin extends.

  • Plugin.js in src/main/assets/plugins/opentelemetry/ – the JavaScript client, byte-identical to the Xcode plugin.

  • io.opentelemetry:opentelemetry-api and io.opentelemetry:opentelemetry-sdk 1.30.0, declared in the module’s build.gradle.kts.