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Use R2 from Workers

1. Create a new application with C3

C3 (create-cloudflare-cli) is a command-line tool designed to help you set up and deploy Workers & Pages applications to Cloudflare as fast as possible.

To get started, open a terminal window and run:

Terminal window
npm create cloudflare@latest -- r2-worker

For setup, select the following options:

  • For What would you like to start with?, choose Hello World example.
  • For Which template would you like to use?, choose Hello World Worker.
  • For Which language do you want to use?, choose JavaScript.
  • For Do you want to use git for version control?, choose Yes.
  • For Do you want to deploy your application?, choose No (we will be making some changes before deploying).

Then, move into your newly created directory:

Terminal window
cd r2-worker

2. Create your bucket

Create your bucket by running:

Terminal window
npx wrangler r2 bucket create <YOUR_BUCKET_NAME>

To check that your bucket was created, run:

Terminal window
npx wrangler r2 bucket list

After running the list command, you will see all bucket names, including the one you have just created.

3. Bind your bucket to a Worker

You will need to bind your bucket to a Worker.

To bind your R2 bucket to your Worker, add the following to your Wrangler file. Update the binding property to a valid JavaScript variable identifier and bucket_name to the <YOUR_BUCKET_NAME> you used to create your bucket in step 2:

{
  "r2_buckets": [
    {
      "binding": "MY_BUCKET",
      "bucket_name": "<YOUR_BUCKET_NAME>"
    }
  ]
}

Find more detailed information on configuring your Worker in the Wrangler Configuration documentation.

4. Access your R2 bucket from your Worker

Within your Worker code, your bucket is now available under the MY_BUCKET variable and you can begin interacting with it.

An R2 bucket is able to READ, LIST, WRITE, and DELETE objects. You can see an example of all operations below using the Module Worker syntax. Add the following snippet into your project's index.js file:

export default {
  async fetch(request, env) {
    const url = new URL(request.url);
    const key = url.pathname.slice(1);


    switch (request.method) {
      case "PUT":
        await env.MY_BUCKET.put(key, request.body);
        return new Response(`Put ${key} successfully!`);
      case "GET":
        const object = await env.MY_BUCKET.get(key);


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


        const headers = new Headers();
        object.writeHttpMetadata(headers);
        headers.set("etag", object.httpEtag);


        return new Response(object.body, {
          headers,
        });
      case "DELETE":
        await env.MY_BUCKET.delete(key);
        return new Response("Deleted!");


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

5. Bucket access and privacy

With the above code added to your Worker, every incoming request has the ability to interact with your bucket. This means your bucket is publicly exposed and its contents can be accessed and modified by undesired actors.

You must now define authorization logic to determine who can perform what actions to your bucket. This logic lives within your Worker's code, as it is your application's job to determine user privileges. The following is a short list of resources related to access and authorization practices:

  1. Basic Authentication: Shows how to restrict access using the HTTP Basic schema.
  2. Using Custom Headers: Allow or deny a request based on a known pre-shared key in a header.

Continuing with your newly created bucket and Worker, you will need to protect all bucket operations.

For PUT and DELETE requests, you will make use of a new AUTH_KEY_SECRET environment variable, which you will define later as a Wrangler secret.

For GET requests, you will ensure that only a specific file can be requested. All of this custom logic occurs inside of an authorizeRequest function, with the hasValidHeader function handling the custom header logic. If all validation passes, then the operation is allowed.

const ALLOW_LIST = ["cat-pic.jpg"];


// Check requests for a pre-shared secret
const hasValidHeader = (request, env) => {
  return request.headers.get("X-Custom-Auth-Key") === env.AUTH_KEY_SECRET;
};


function authorizeRequest(request, env, key) {
  switch (request.method) {
    case "PUT":
    case "DELETE":
      return hasValidHeader(request, env);
    case "GET":
      return ALLOW_LIST.includes(key);
    default:
      return false;
  }
}


export default {
  async fetch(request, env, ctx) {
    const url = new URL(request.url);
    const key = url.pathname.slice(1);


    if (!authorizeRequest(request, env, key)) {
      return new Response("Forbidden", { status: 403 });
    }


    // ...
  },
};

For this to work, you need to create a secret via Wrangler:

Terminal window
npx wrangler secret put AUTH_KEY_SECRET

This command will prompt you to enter a secret in your terminal:

Terminal window
npx wrangler secret put AUTH_KEY_SECRET
Enter the secret text you'd like assigned to the variable AUTH_KEY_SECRET on the script named <YOUR_WORKER_NAME>:
*********
🌀  Creating the secret for script name <YOUR_WORKER_NAME>
✨  Success! Uploaded secret AUTH_KEY_SECRET.

This secret is now available as AUTH_KEY_SECRET on the env parameter in your Worker.

6. Deploy your bucket

With your Worker and bucket set up, run the npx wrangler deploy command to deploy to Cloudflare's global network:

Terminal window
npx wrangler deploy

You can verify your authorization logic is working through the following commands, using your deployed Worker endpoint:

Terminal window
# Attempt to write an object without providing the "X-Custom-Auth-Key" header
curl https://your-worker.dev/cat-pic.jpg -X PUT --data-binary 'test'
#=> Forbidden
# Expected because header was missing


# Attempt to write an object with the wrong "X-Custom-Auth-Key" header value
curl https://your-worker.dev/cat-pic.jpg -X PUT --header "X-Custom-Auth-Key: hotdog" --data-binary 'test'
#=> Forbidden
# Expected because header value did not match the AUTH_KEY_SECRET value


# Attempt to write an object with the correct "X-Custom-Auth-Key" header value
# Note: Assume that "*********" is the value of your AUTH_KEY_SECRET Wrangler secret
curl https://your-worker.dev/cat-pic.jpg -X PUT --header "X-Custom-Auth-Key: *********" --data-binary 'test'
#=> Put cat-pic.jpg successfully!


# Attempt to read object called "foo"
curl https://your-worker.dev/foo
#=> Forbidden
# Expected because "foo" is not in the ALLOW_LIST


# Attempt to read an object called "cat-pic.jpg"
curl https://your-worker.dev/cat-pic.jpg
#=> test
# Note: This is the value that was successfully PUT above

By completing this guide, you have successfully installed Wrangler and deployed your R2 bucket to Cloudflare.

  1. Workers Tutorials
  2. Workers Examples