Cloudflare Workers are serverless functions that run on Cloudflare’s global network. Often, you want to trigger a Cloudflare Worker when a database row changes. For example, you may want to trigger a worker as a side-effect of a database change, or fan out work to multiple services.
Cloudflare Worker
In this guide, you will learn how to setup Sequin to trigger a Cloudflare Worker when a database row changes.

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Prerequisites

You are about to create a simple Cloudflare Worker that logs a message to the console. You’ll trigger this worker by setting up a Webhook sink in Sequin that sends a HTTP POST request to the worker’s URL with the payload of the database row that changed. You’ll need the following:

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Create a Cloudflare Worker

Start by creating a new Cloudflare Worker that takes in a Sequin change event as a payload and logs the payload to the console.
1

Create a new Cloudflare Worker

  1. Log in to your Cloudflare dashboard and navigate to the “Workers and Pages” section.
  2. Click on “Create Worker”.
  3. Give your service a name (e.g., “user-worker”) and click “Deploy”.
Cloudflare will create a new worker.
2

Add worker code

Click the Edit code button.Replace the default code in the worker editor with the following:
export default {
  async fetch(request, env) {
    // Verify the Sequin webhook secret
    const authHeader = request.headers.get('authorization');
    if (!authHeader || authHeader !== `Bearer ${env.SEQUIN_WEBHOOK_SECRET}`) {
      return new Response('Unauthorized', { status: 401 });
    }

    try {
      const payload = await request.json();
      const { record } = payload;

      if (record && record.name) {
        console.log(`Hello ${record.name}`);
      } else {
        console.log('No name found in the payload.');
      }

      return new Response('Success', { status: 200 });
    } catch (error) {
      console.error('Error processing request:', error);
      return new Response('Internal Server Error', { status: 500 });
    }
  },
};
This worker first checks the authorization header to make sure the request is coming from Sequin. Then it processes the payload and logs a message to the console. In this example code, the row that changed contains a name field, so the worker logs the name to the console.Click the Deploy button to deploy your worker.
3

Add the SEQUIN_WEBHOOK_SECRET environment variable

  1. In your worker’s settings, go to the “Settings” tab.
  2. Scroll down to the “Variables and Secrets” section.
  3. Click ”+ Add”.
  4. Set the variable name as SEQUIN_WEBHOOK_SECRET and the value to a secure secret of your choice.
  5. Click “Deploy”.
Keep this secret handy. You will need to use this secret value in the Sequin dashboard when you create the push consumer.
4

Get the worker's URL

Under the “Settings” tab, find the “Domains & Routes” section.Copy the worker’s URL. You will need this URL in the Sequin dashboard when you create the push consumer.
You’ve successfully created a Cloudflare Worker that logs a message to the console when Sequin sends a HTTP POST request to the worker’s URL.

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Create a webhook sink

Create a webhook sink that captures changes to your database and sends a HTTP POST request to the Cloudflare Worker’s URL:
1

Create a new sink

Navigate to the “Sinks” tab, click the “Create Sink” button, and select “Webhook Sink”.
2

Select source table(s)

Select the schemas and tables you want to capture changes from (i.e public.users or public).
3

Add filters (optional)

Add filters to the sink to control which database changes are sent to your webhook endpoint.
4

Configure backfill

You can optionally indicate if you want your webhook endpoint to receive a backfill of all or a portion of the table’s existing data. For now, leave “Backfill” toggled off.
5

Configure message grouping

Under “Message grouping”, leave the default option selected to ensure events for the same row are sent to your webhook endpoint in order.
6

Configure sink settings

Under “Webhook Sink configuration” leave the defaults:
  • Leave the default value of 30000 ms for “Request timeout” as this is more than enough time for your worker to process the request
  • Leave the default value of 1 for “Batch size” so each change is processed individually.
7

Configure HTTP endpoint

Under “HTTP Endpoint”, enter the Cloudflare Worker’s URL you copied earlier. Then click to “Add Encrypted Header” with the key Authorization and the value Bearer SEQUIN_WEBHOOK_SECRET, using the secret value you set in your worker’s environment variables.
8

Name and create sink

Give your sink a name (i.e. users_webhook_sink) and click “Create Webhook Sink”.
Your webhook sink is now created and ready to send events to your Cloudflare Worker.

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Test end-to-end

1

Create a row in your database

For example, insert a row into the users table:
insert into
users (name)
values
  (
    'John Doe'
  );
2

Trace the change in the Sequin dashboard

In the Sequin console, open the Messages tab on your webhook sink and confirm that a message was delivered.
3

Confirm the event was received by your Cloudflare Worker

  1. Go to your Cloudflare dashboard and navigate to your worker.
  2. Click on the “Logs” tab.
  3. You should see a log entry. For example:Hello John Doe:
Confirm message
You’ve successfully triggered a Cloudflare Worker from a database change!

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Next steps

Modify this example to suit your needs:
  • If you need to run long-running jobs, consider using Cloudflare Durable Objects in tandem with Workers.
  • Tune your webhook sink configuration to suit your volume of work.
  • Implement additional security measures, such as Cloudflare Access for enhanced authentication and authorization.