Deno

OpenTelemetry is built into Deno, so there's nothing to install. Turning it on yields traces for Deno.serve and fetch, HTTP server metrics, and every console.log as a log.

Prerequisites

An OpenTelemetry Stream and an ingest key for that Stream. See OpenTelemetry → Prerequisites. Deno 2.4 or newer is required.

1. Configure

OTEL_DENO=true
OTEL_SERVICE_NAME=checkout-api
OTEL_EXPORTER_OTLP_ENDPOINT=https://ws.latency.app/v1/ingest
OTEL_EXPORTER_OTLP_HEADERS=authorization=Bearer%20lit_XXXXXXXXXXX
OTEL_EXPORTER_OTLP_METRICS_TEMPORALITY_PREFERENCE=delta

OTEL_DENO=true is the switch. Deno already sends over HTTP, so there's no protocol to set.

Deno always sends all three signals, and one OpenTelemetry Stream takes them all.

2. Run

Start the app as usual:

deno run -A main.ts

3. Check it's working

Make a few requests to the app, then open Telemetry in the Console, pick the Stream and choose Traces. Traces show up within seconds. Metrics follow within a minute.

Custom spans

Deno sets up @opentelemetry/api automatically, so a plain import works:

import { trace } from "npm:@opentelemetry/api@1";

const tracer = trace.getTracer("checkout");

await tracer.startActiveSpan("charge-card", async (span) => {
  try {
    span.setAttribute("order.id", order.id);
    await chargeCard(order);
  } finally {
    span.end();
  }
});

Custom metrics

import { metrics } from "npm:@opentelemetry/api@1";

const meter = metrics.getMeter("checkout");
const orders = meter.createCounter("orders.placed");
const duration = meter.createHistogram("checkout.duration", { unit: "ms" });

orders.add(1, { plan: "pro" });
duration.record(182, { route: "/pay" });

Logs

Every console.log, console.warn and console.error goes to the Stream's logs, linked to the surrounding trace, and still prints to the terminal. To send logs to Telemetry only, set OTEL_DENO_CONSOLE=replace; to keep console output out of Telemetry, set OTEL_DENO_CONSOLE=ignore.