Trigger Cloudflare Workers from database changes

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.

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 (which contains the database row that changed) and logs the name from the payload to the console.

Click the Deploy button to deploy your worker.

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”.

You will need to use this secret value in the Sequin dashboard when you create the push consumer.

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.

1. Login to your Sequin account and click the Add New Database button.
2. Enter the connection details for your Postgres database.
3. Follow the instructions to create a publication and a replication slot by running two SQL commands in your database:

create publication sequin_pub for all tables;
select pg_create_logical_replication_slot('sequin_slot', 'pgoutput');

4. Name your database and click the Connect Database button.

Sequin will connect to your database and ensure that it’s configured properly.

Create a push consumer that will capture users from your database and deliver them to your Cloudflare Worker:

1. Navigate to the Consumers tab and click the Create Consumer button.
2. Select your users table (i.e public.users).
3. For this guide, you want to capture all changes to the users table. To do this, select Changes and click Continue.
4. Select to capture inserts, updates, and deletes. No need to add a filter for now. Click Continue.
5. On the next screen, select Push to have Sequin send the events to your webhook URL. Click Continue.
6. Now, give your consumer a name (i.e. users_push_consumer) and in the HTTP Endpoint section, click New HTTP Endpoint.
7. Enter your Cloudflare Worker’s URL. Then click to Add Encrypted Header and add an encryption header with the key Authorization and the value Bearer SEQUIN_WEBHOOK_SECRET, using the secret value you set in your worker’s environment variables. Click Create Endpoint.
8. Back in the tab where you were creating your consumer, click the refresh button by the Endpoints section and select the endpoint you just created. Click Create Consumer.

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

1. Go to your Cloudflare dashboard and navigate to your worker.
2. Click on the “Logs” tab.
3. You should see a log entry: Hello John Doe: