As organizations increasingly rely on cloud storage solutions, effective data replication between storage buckets is crucial. However, as many have discovered, Cloudflare’s R2 storage does not support direct replication between different R2 buckets. To solve this challenge, I developed a custom solution using Cloudflare Workers. This blog post will walk you through how to set up R2 bucket bindings in the Cloudflare dashboard and share the Worker script I created for moving data between buckets.

Setting Up R2 Bucket Bindings

Before we dive into the Worker script, let’s first understand how to bind R2 buckets to your Cloudflare Worker. Here’s a step-by-step guide to configuring an R2 bucket binding via the Cloudflare dashboard:

1. Log In: Begin by logging into your Cloudflare dashboard.
2. Navigate to Workers & Pages: In the Account Home screen, select the Workers & Pages section.
3. Select Your Project: Click on your specific Pages project that you want to work with.
4. Access Settings: Go to Settings > Functions > R2 bucket bindings.
5. Add Binding: Click on Add binding to set up a new binding.
6. Production or Preview Environment: Choose whether you want to configure the binding for your Production or Preview environment.
7. Name Your Binding: Provide a name for your binding under Variable name. This will be how you reference your bucket within your Worker script.
8. Select R2 Bucket: Choose your desired R2 bucket from the list.
9. Repeat for Preview: If applicable, repeat steps 5 and 6 for both the Production and Preview environments.
10. Redeploy Your Project: Once you’ve added the bindings, be sure to redeploy your project for the changes to take effect.

Following these steps will successfully bind your R2 buckets to your Cloudflare Workers project, allowing you to access them programmatically.

The Cloudflare Worker Script

Now, let’s look at the Worker script that handles the replication of objects from one R2 bucket to another. Here is the script:

export default {
  async fetch(request, env) {
    switch (request.method) {
      case "GET":
        const listobj = await env.sourcebucket.list();
        let keys = listobj.objects.map(obj => obj.key);
        let successResponses = [];

        for (var i = 0; i < keys.length; i++) {
          const object = await env.sourcebucket.get(keys[i]);
          console.log(keys[i]);

          if (object === null) {
            return new Response("Object Not Found", { status: 404 });
          }

          await env.destinationbucket.put(keys[i], object.body);
          successResponses.push(`Put ${keys[i]} successfully!`);
        }

        return new Response(successResponses.join(", "), { status: 200 });

      default:
        return new Response("Method Not Allowed", {
          status: 405,
          headers: {
            Allow: "PUT, GET, LIST",
          },
        });
    }
  },
};

How the Script Works

1. Request Handling: The script listens for incoming HTTP requests. In this case, it specifically responds to GET requests.
2. Listing Objects: When a GET request is made, it retrieves a list of objects from the source R2 bucket (env.sourcebucket).
3. Fetching and Replicating: The script iterates through the list of object keys, fetching each object from the source bucket. If an object is not found, it returns a 404 error. Each successfully fetched object is then stored in the destination bucket (env.destinationbucket).
4. Success Responses: The script collects success messages as it replicates each object and returns a combined response indicating the successful operations.
5. Error Handling: Any methods beyond GET will result in a “Method Not Allowed” response with an appropriate status code.

Conclusion

With Cloudflare Workers and R2 storage, you can efficiently manage data replication between your buckets. By following the steps outlined above and utilizing the provided Worker script, you can create a reliable solution tailored to your specific requirements. While Cloudflare’s native support for R2 replication might be limited, the versatility of Workers allows developers to implement custom solutions with ease.

Feel free to reach out with any questions or share your experiences with R2 bucket replication in the comments below! Happy coding!