Telemetry

Source: src/Cloudflare/Workers/Telemetry.ts Kind: Layer · Provides: Tracer.Tracer

Mirror Effect spans into Cloudflare Workers Observability.

A binding layer: at deploy time it turns on observability.traces on the host Worker (the same path as Cloudflare.cache()) and registers a per-event Effect Tracer. Cloudflare auto-instruments fetch/KV/R2/D1; Effect.withSpan / Effect.fn frames nest in that waterfall. Cloudflare owns sampling and export — no OTLP URL, flush, or Wrangler block.

Until the global default compatibility date is raised past 2026-07-28, pin compatibility: { date: "2026-08-25" } (or later) or deploy fails. alchemy dev does not gate the date: what a local Worker records is the local runtime’s concern.

Compose it into the Function/Worker’s single Effect.provide:

Enabling native tracing

export default Cloudflare.Worker(
  "Worker",
  {
    main: import.meta.url,
    compatibility: { date: "2026-08-25" },
  },
  Effect.gen(function* () {
    return {
      fetch: Effect.gen(function* () {
        yield* doWork().pipe(Effect.withSpan("operation"));
        return HttpServerResponse.text("ok");
      }),
    };
  }).pipe(
    Effect.provide(
      Layer.mergeAll(
        Cloudflare.R2.ReadWriteBucketBinding,
        Cloudflare.Telemetry(),
      ),
    ),
  ),
);

Combining with other exporters

Effect.provide(
  Layer.mergeAll(
    Cloudflare.Telemetry(),
    // omit `traces` — Cloudflare.Telemetry provides the Tracer
    Axiom.Telemetry({ token: Ingest, logs: Logs, metrics: Metrics }),
  ),
)

To ship the same waterfall (Effect + platform spans) elsewhere, export it from Cloudflare with Cloudflare.Workers.ObservabilityDestination rather than sending a second Worker-side OTLP trace stream.