@opentelemetry/instrumentation-fastify

What is @opentelemetry/instrumentation-fastify?

@opentelemetry/instrumentation-fastify is an npm package that provides automatic instrumentation for Fastify applications using OpenTelemetry. It helps in collecting and exporting telemetry data such as traces and metrics, which can be used for monitoring and performance analysis.

What are @opentelemetry/instrumentation-fastify's main functionalities?

Automatic Tracing

This code demonstrates how to set up automatic tracing for a Fastify application using @opentelemetry/instrumentation-fastify. It initializes the OpenTelemetry tracer provider and registers the Fastify instrumentation to automatically collect trace data for incoming requests.

const { NodeTracerProvider } = require('@opentelemetry/sdk-trace-node');
const { registerInstrumentations } = require('@opentelemetry/instrumentation');
const { FastifyInstrumentation } = require('@opentelemetry/instrumentation-fastify');

const provider = new NodeTracerProvider();
provider.register();

registerInstrumentations({
  instrumentations: [
    new FastifyInstrumentation()
  ],
  tracerProvider: provider,
});

const fastify = require('fastify')();

fastify.get('/hello', async (request, reply) => {
  return { hello: 'world' };
});

fastify.listen(3000, err => {
  if (err) throw err;
  console.log('Server listening on http://localhost:3000');
});

Custom Span Attributes

This code sample shows how to add custom attributes to spans in a Fastify application. The `requestHook` option allows you to modify the span for each request, adding custom attributes that can be useful for more detailed telemetry data.

const { NodeTracerProvider } = require('@opentelemetry/sdk-trace-node');
const { registerInstrumentations } = require('@opentelemetry/instrumentation');
const { FastifyInstrumentation } = require('@opentelemetry/instrumentation-fastify');

const provider = new NodeTracerProvider();
provider.register();

registerInstrumentations({
  instrumentations: [
    new FastifyInstrumentation({
      requestHook: (span, request) => {
        span.setAttribute('http.custom_attribute', 'custom_value');
      }
    })
  ],
  tracerProvider: provider,
});

const fastify = require('fastify')();

fastify.get('/hello', async (request, reply) => {
  return { hello: 'world' };
});

fastify.listen(3000, err => {
  if (err) throw err;
  console.log('Server listening on http://localhost:3000');
});

Other packages similar to @opentelemetry/instrumentation-fastify

@opentelemetry/instrumentation-express

@opentelemetry/instrumentation-express provides similar functionality for Express applications. It allows for automatic tracing and custom span attributes, but is specifically designed for the Express framework rather than Fastify.

@opentelemetry/instrumentation-hapi

@opentelemetry/instrumentation-hapi offers automatic instrumentation for Hapi.js applications. Like @opentelemetry/instrumentation-fastify, it helps in collecting and exporting telemetry data, but it is tailored for the Hapi.js framework.

@opentelemetry/instrumentation-koa

@opentelemetry/instrumentation-koa provides automatic instrumentation for Koa applications. It is similar to @opentelemetry/instrumentation-fastify in terms of functionality but is designed for the Koa framework.

README

OpenTelemetry Fastify Instrumentation for Node.js

[!IMPORTANT] This component is deprecated in favor of the official instrumentation package @fastify/otel, maintained by the Fastify authors. Please see here for instructions on how to use @fastify/otel.

We will stop publishing new versions of @opentelemetry/instrumentation-fastify on June 30, 2025.

This module provides automatic instrumentation for the fastify module, which may be loaded using the @opentelemetry/sdk-trace-node package.

Compatible with OpenTelemetry JS API and SDK 1.0+.

Installation

This instrumentation relies on HTTP calls to also be instrumented. Make sure you install and enable both, otherwise you will have spans that are not connected with each other.

npm install --save @opentelemetry/instrumentation-http @opentelemetry/instrumentation-fastify

Supported Versions

• fastify versions >=3.0.0 <5

Usage

OpenTelemetry fastify Instrumentation allows the user to automatically collect trace data and export them to their backend of choice, to give observability to distributed systems.

To load the instrumentation, specify it in the Node Tracer's configuration:

const { NodeTracerProvider } = require('@opentelemetry/node');
const { registerInstrumentations } = require('@opentelemetry/instrumentation');
const { HttpInstrumentation } = require('@opentelemetry/instrumentation-http');
const { FastifyInstrumentation } = require('@opentelemetry/instrumentation-fastify');

const provider = new NodeTracerProvider();
provider.register();

registerInstrumentations({
  instrumentations: [
    // Fastify instrumentation expects HTTP layer to be instrumented
    new HttpInstrumentation(),
    new FastifyInstrumentation(),
  ],
});

See examples/fastify for a short example.

Fastify Instrumentation Options

Options	Type	Example	Description
requestHook	FastifyCustomAttributeFunction	(span, requestInfo) => {}	Function for adding custom attributes to Fastify requests. Receives parameters: Span, FastifyRequestInfo.

Using requestHook

Instrumentation configuration accepts a custom "hook" function which will be called for every instrumented Fastify request. Custom attributes can be set on the span or run any custom logic per request.

import { FastifyInstrumentation } from "@opentelemetry/instrumentation-fastify"

const fastifyInstrumentation = new FastifyInstrumentation({
  requestHook: function (span: Span, info: FastifyRequestInfo) {
    span.setAttribute(
      'http.method',
      info.request.method,
    )
  }
});

Semantic Conventions

This package uses @opentelemetry/semantic-conventions version 1.22+, which implements Semantic Convention Version 1.7.0

Attributes collected:

Attribute	Short Description
http.route	The matched route (path template).

Useful links

• For more information on OpenTelemetry, visit: https://opentelemetry.io/
• For more about OpenTelemetry JavaScript: https://github.com/open-telemetry/opentelemetry-js
• For help or feedback on this project, join us in GitHub Discussions

License

Apache 2.0 - See LICENSE for more information.