How does @hono/otel work with Deno OTEL

[mirshko]

Would like to know how to properly set up Hono OTEL with Deno's native OTEL support.

[blockchainGuru1018]

✅ Step 1: Enable Deno's Native OpenTelemetry Support
Deno provides built-in support for OpenTelemetry. To enable it, set the OTEL_DENO environment variable to true when running your application:
OTEL_DENO=true deno run --allow-env --allow-net --unstable server.ts
This command enables automatic instrumentation for Deno's runtime, including HTTP requests and fetch calls. It also sets up context propagation and exports telemetry data to the OpenTelemetry Protocol (OTLP) endpoint at localhost:4318 by default

✅ Step 2: Install and Configure @hono/otel Middleware
The @hono/otel middleware instruments your Hono application with OpenTelemetry. To use it, import and apply it to your Hono app:

import { Hono } from '@honojs/hono'
import { otel } from '@hono/otel'

const app = new Hono()

app.use(otel()) // Apply OpenTelemetry middleware

app.get('/', (c) => c.text('Hello, World!'))

export default app

This middleware automatically instruments incoming HTTP requests and outgoing fetch calls, creating spans for tracing

✅ Step 3: Set Up an OpenTelemetry Collector (Optional)
If you're using a custom OpenTelemetry backend or need to export telemetry data, set up an OpenTelemetry Collector. For example, to export data to Honeycomb, configure the collector as follows:

receivers:
  otlp:
    protocols:
      http:
        endpoint: 0.0.0.0:4318

exporters:
  otlphttp:
    endpoint: "https://api.honeycomb.io:443"
    headers:
      "x-honeycomb-team": "<YOUR_API_KEY>"

service:
  pipelines:
    traces:
      receivers: [otlp]
      exporters: [otlphttp]

Run the collector using Docker:
docker run -p 4318:4318 -v $(pwd)/otel-collector-config.yaml:/etc/otel-collector-config.yaml otel/opentelemetry-collector-contrib:latest --config /etc/otel-collector-config.yaml
Then, run your Deno application with the appropriate environment variables to export telemetry data to the collector:

OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4318 \
OTEL_SERVICE_NAME=my-hono-app \
OTEL_DENO=true \
deno run --allow-env --allow-net server.ts

This setup allows you to monitor your Hono application using your chosen observability platform

✅ Step 4: Customize Tracing (Optional)
To add custom attributes or adjust span names, use the OpenTelemetry API within your route handlers:

import { trace } from '@opentelemetry/api'

app.get('/users/:id', (c) => {
  const span = trace.getActiveSpan()
  span?.setAttribute('custom.attribute', 'value')
  return c.json({ id: c.req.param('id') })
})

This allows for more granular control over your tracing data

✅ Step 5: Verify and Monitor
After setting up, verify that telemetry data is being collected:

• Check your observability platform (e.g., Honeycomb, Grafana) for traces, metrics, and logs.
• Use the OTEL_LOG_LEVEL=debug environment variable to enable detailed logging for troubleshooting.

For more detailed guidance, refer to the Deno documentation on OpenTelemetry integration