OpenTelemetry using Cloudflare Workers

This guide demonstrates how to configure OpenTelemetry in Cloudflare Workers to send telemetry data to Axiom using the OTel CF Worker package.

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Prerequisites

• Create an Axiom account.
• Create a dataset in Axiom where you will send your data.
• Create an API token in Axiom with permissions to query and ingest data.
• Create a Cloudflare account.
• Install Wrangler, the CLI tool for Cloudflare.

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Setting up your Cloudflare Workers environment

Create a new directory for your project and navigate into it:

mkdir my-axiom-worker && cd my-axiom-worker

Initialize a new Wrangler project using this command:

wrangler init --type="javascript"

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Cloudflare Workers Script Configuration (index.ts)

Configure and implement your Workers script by integrating OpenTelemetry with the @microlabs/otel-cf-workers package to send telemetry data to Axiom, as illustrated in the example index.ts below:

// index.ts
import { trace } from '@opentelemetry/api';
import { instrument, ResolveConfigFn } from '@microlabs/otel-cf-workers';

export interface Env {
  AXIOM_API_TOKEN: string,
  AXIOM_DATASET: string
}

const handler = {
  async fetch(request: Request, env: Env, ctx: ExecutionContext): Promise<Response> {
    await fetch('https://cloudflare.com');
    const greeting = "Welcome to Axiom Cloudflare instrumentation";
    trace.getActiveSpan()?.setAttribute('greeting', greeting);
    ctx.waitUntil(fetch('https://workers.dev'));
    return new Response(`${greeting}!`);
  },
};

const config: ResolveConfigFn = (env: Env, _trigger) => {
  return {
    exporter: {
      url: 'https://api.axiom.co/v1/traces',
      headers: {
        'Authorization': `Bearer ${env.AXIOM_API_TOKEN}`,
        'X-Axiom-Dataset': `${env.AXIOM_DATASET}`
      },
    },
    service: { name: 'axiom-cloudflare-workers' },
  };
};

export default instrument(handler, config);

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Wrangler Configuration (wrangler.toml)

Configure wrangler.toml with your Cloudflare account details and set environment variables for the Axiom API token and dataset.

name = "my-axiom-worker"
type = "javascript"
account_id = "$YOUR_CLOUDFLARE_ACCOUNT_ID" # Replace with your actual Cloudflare account ID
workers_dev = true
compatibility_date = "2023-03-27"
compatibility_flags = ["nodejs_compat"]
main = "index.ts"

# Define environment variables here
[vars]
AXIOM_API_TOKEN = "$API_TOKEN" # Replace $API_TOKEN with your actual Axiom API token
AXIOM_DATASET = "$DATASET" # Replace $DATASET with your actual Axiom dataset name

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Install Dependencies

Navigate to the root directory of your project and add @microlabs/otel-cf-workers and other OTel packages to the package.json file.

{
    "name": "my-axiom-worker",
    "version": "1.0.0",
    "description": "A template for kick-starting a Cloudflare Workers project",
    "main": "index.ts",
    "scripts": {
      "start": "wrangler dev",
      "deploy": "wrangler publish"
    },
    "dependencies": {
      "@microlabs/otel-cf-workers": "^1.0.0-rc.20",
      "@opentelemetry/api": "^1.6.0",
      "@opentelemetry/core": "^1.17.1",
      "@opentelemetry/exporter-trace-otlp-http": "^0.43.0",
      "@opentelemetry/otlp-exporter-base": "^0.43.0",
      "@opentelemetry/otlp-transformer": "^0.43.0",
      "@opentelemetry/resources": "^1.17.1",
      "@opentelemetry/sdk-trace-base": "^1.17.1",
      "@opentelemetry/semantic-conventions": "^1.17.1",
      "deepmerge": "^4.3.1",
      "husky": "^8.0.3",
      "lint-staged": "^15.0.2",
      "ts-checked-fsm": "^1.1.0"
    },
    "devDependencies": {
      "@changesets/cli": "^2.26.2",
      "@cloudflare/workers-types": "^4.20231016.0",
      "prettier": "^3.0.3",
      "rimraf": "^4.4.1",
      "typescript": "^5.2.2",
      "wrangler": "2.13.0"
    },
    "private": true
  }

Run npm install to install the packages. This command will install all the necessary packages listed in your package.json file.

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Running the instrumented app

To run your Cloudflare Workers app with OpenTelemetry instrumentation, ensure your API token and dataset are correctly set in your wrangler.toml file. As outlined in our package.json file, you have two primary scripts to manage your app’s lifecycle.

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In development mode

For local development and testing, you can start a local development server by running:

npm run start

This command runs wrangler dev allowing you to preview and test your app locally.

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Deploying to production

Deploy your app to the Cloudflare Workers environment by running:

npm run deploy

This command runs wrangler publish, deploying your project to Cloudflare Workers.

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Alternative: Use Wrangler directly

If you prefer not to use npm commands or want more direct control over the deployment process, you can use Wrangler commands directly in your terminal.

For local development:

wrangler dev

For deploying to Cloudflare Workers:

wrangler deploy

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View your app in Cloudflare Workers

Once you’ve deployed your app using Wrangler, view and manage it through the Cloudflare dashboard. To see your Cloudflare Workers app, follow these steps:

• In your Cloudflare dashboard, click Workers & Pages to access the Workers section. You see a list of your deployed apps.

• Locate your app by its name. For this tutorial, look for my-axiom-worker.

• Click your app’s name to view its details. Within the app’s page, select the triggers tab to review the triggers associated with your app.

• Under the routes section of the triggers tab, you will find the URL route assigned to your Worker. This is where your Cloudflare Worker responds to incoming requests. Vist the Cloudflare Workers documentation to learn how to configure routes

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Observe the telemetry data in Axiom

As you interact with your app, traces will be collected and exported to Axiom, allowing you to monitor, analyze, and gain insights into your app’s performance and behavior.

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Dynamic OpenTelemetry traces dashboard

This data can then be further viewed and analyzed in Axiom’s dashboard, offering a deeper understanding of your app’s performance and behavior.

Working with Cloudflare Pages Functions: Integration with OpenTelemetry is similar to Workers but uses the Cloudflare Dashboard for configuration, bypassing wrangler.toml. This simplifies setup through the Cloudflare dashboard web interface.

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Manual Instrumentation

Manual instrumentation requires adding code into your Worker’s script to create and manage spans around the code blocks you want to trace.

1. Initialize Tracer:

Use the OpenTelemetry API to create a tracer instance at the beginning of your script using the @microlabs/otel-cf-workers package.

import { trace } from '@opentelemetry/api';
const tracer = trace.getTracer('your-service-name');

2. Create start and end Spans:

Manually start spans before the operations or events you want to trace and ensure you end them afterward to complete the tracing lifecycle.

const span = tracer.startSpan('operationName');
try {
  // Your operation code here
} finally {
  span.end();
}

3. Annotate Spans:

Add important metadata to spans to provide additional context. This can include setting attributes or adding events within the span.

span.setAttribute('key', 'value');
span.addEvent('eventName', { 'eventAttribute': 'value' });

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Automatic Instrumentation

Automatic instrumentation uses the @microlabs/otel-cf-workers package to automatically trace incoming requests and outbound fetch calls without manual span management.

1. Instrument your Worker:

Wrap your Cloudflare Workers script with the instrument function from the @microlabs/otel-cf-workers package. This automatically instruments incoming requests and outbound fetch calls.

import { instrument } from '@microlabs/otel-cf-workers';

export default instrument(yourHandler, yourConfig);

2. Configuration: Provide configuration details, including how to export telemetry data and service metadata to Axiom as part of the instrument function call.

const config = (env) => ({
  exporter: {
    url: 'https://api.axiom.co/v1/traces',
    headers: {
      'Authorization': `Bearer ${env.AXIOM_API_TOKEN}`,
      'X-Axiom-Dataset': `${env.AXIOM_DATASET}`
    },
  },
  service: { name: 'axiom-cloudflare-workers' },
});

After instrumenting your Worker script, the @microlabs/otel-cf-workers package takes care of tracing automatically.

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Reference

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List of OpenTelemetry trace fields

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List of imported libraries

@microlabs/otel-cf-workers

This package is designed for integrating OpenTelemetry within Cloudflare Workers. It provides automatic instrumentation capabilities, making it easier to collect telemetry data from your Workers apps without extensive manual instrumentation. This package simplifies tracing HTTP requests and other asynchronous operations within Workers.

@opentelemetry/api

The core API for OpenTelemetry in JavaScript, providing the necessary interfaces and utilities for tracing, metrics, and context propagation. In the context of Cloudflare Workers, it allows developers to manually instrument custom spans, manipulate context, and access the active span if needed.

@opentelemetry/exporter-trace-otlp-http

This exporter enables your Cloudflare Workers app to send trace data over HTTP to any backend that supports the OTLP (OpenTelemetry Protocol), such as Axiom. Using OTLP ensures compatibility with a wide range of observability tools and standardizes the data export process.

@opentelemetry/otlp-exporter-base, @opentelemetry/otlp-transformer

These packages provide the foundational elements for OTLP exporters, including the transformation of telemetry data into the OTLP format and base classes for implementing OTLP exporters. They are important for ensuring that the data exported from Cloudflare Workers adheres to the OTLP specification.

@opentelemetry/resources

Defines the Resource, which represents the entity producing telemetry. In Cloudflare Workers, Resources can be used to describe the worker (for example,, service name, version) and are attached to all exported telemetry, aiding in identifying data in backend systems.