Better Stack Cloudflare Workers logging

Start logging in 5 minutes

Collect logs from your Cloudflare Workers.

Create a new source

Create a new JavaScript • Node.js source in Better Stack Logs.

Set up Cloudflare Worker

Either open your existing project with Wrangler CLI if you already have it set up, or initialize new "Hello World" Worker:

wrangler login
wrangler init better-stack-logging-example
cd better-stack-logging-example

Install Better Stack logging library

Install Better Stack logging library for edge JS runtime @logtail/edge:

npm install --save @logtail/edge

Create and use instance of logger

Import and instantiate Logtail class, add the execution context from the request, and use it for your application logs:

import { Logtail } from "@logtail/edge"

export const baseLogger = new Logtail("$SOURCE_TOKEN", {
  endpoint: 'https://$INGESTING_HOST',
})

export interface Env {
  // ...
}

export default {{
  async fetch(request: Request, env: Env, ctx: ExecutionContext): Promise<Response> {
    const logger = baseLogger.withExecutionContext(ctx)

    logger.debug("I am using Better Stack!")
    logger.info("An interesting event occurred!")

    // Logging structured data
    logger.warn("Something is not quite right, better check on it.",{
      user:{
        username:"someuser",
        email:"someuser@example.com"
      },
      additional_info:{
        tried_accessing: "/url/of/error"
      }
    })

    // Logging application errors
    function callbackThatMightFail() {
      throw new Error("Example error")
    }
    try {
      callbackThatMightFail()
    } catch (err) {
      logger.error("Oops! An runtime ERROR occurred!", err)
    }

    return new Response('Hello world')
  },
}

Deploy your worker

Deploy your worker using Wrangler CLI

wrangler deploy

Finally, open the worker's URL in your browser to run it.

You should see your logs in Better Stack → Live tail.

Additional information

• Instantiating the Logtail class outside of fetch handler method will allow different worker runs to share log queue.

• Providing the ExecutionContext instance (usually called ctx) will ensure all logs will be sent to Better Stack. To ensure best results, always use the returned logger instance from Logtail::withExecutionContext() method.

• Want to learn more about log levels and middleware?
  Continue to the Advanced usage of Logtail JavaScript client.

Logging from environments without ExecutionContext?

Some environments — like Cloudflare Durable Objects — don’t expose the ExecutionContext to your log handler. When this happens, the logger can't schedule log syncing automatically, and you might see a warning like this:

To safely log in these environments:

import { Logtail } from "@logtail/edge"

// Suppress the warning messages
export const logger = new Logtail("$SOURCE_TOKEN", {
  endpoint: 'https://$INGESTING_HOST',
  warnAboutMissingExecutionContext: false,
})

// Use logger as usual
logger.debug("I am using Better Stack!")
logger.info("An interesting event occurred!")

// Ensure logs are sent before the environment shuts down
await logger.flush();

Need help?

Please let us know at hello@betterstack.com.
We're happy to help! 🙏