Local development

To test your Dispatch Worker, user Worker and Outbound Worker before deploying to production, you can use Wrangler for development and testing.

Support for Workers for Platforms with wrangler dev in local mode is experimental and may change in the future. Use the prerelease branch: wrangler@dispatch-namespaces-dev to try Workers for Platforms locally.

1. Create a user worker

npm

npm create cloudflare@latest -- customer-worker-1

yarn

yarn create cloudflare@latest customer-worker-1

pnpm

pnpm create cloudflare@latest customer-worker-1

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 the newly created directory:

cd customer-worker-1

Update the src/index.js file for customer-worker-1:

export default {
  async fetch(request) {
    // make a subrequest to the internet
    const response = await fetch("https://example.com");
    return new Response(
      `user worker got "${await response.text()}" from fetch`,
    );
  },
};

Update the wrangler.toml file for customer-worker-1 and add the dispatch namespace:

# ... other content above ...

dispatch_namespace = "my-namespace"

2. Create a dispatch worker

npm

npm create cloudflare@latest -- dispatch-worker

yarn

yarn create cloudflare@latest dispatch-worker

pnpm

pnpm create cloudflare@latest dispatch-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 the newly created directory:

cd dispatch-worker

Update the src/index.js file for dispatch-worker:

export default {
  async fetch(request, env) {
    // get the user Worker, specifying parameters that the Outbound Worker will see when it intercepts a user worker's subrequest
    const customerScript = env.DISPATCH_NAMESPACE.get(
      "customer-worker-1",
      {},
      {
        outbound: {
          paramCustomerName: "customer-1",
        },
      },
    );
    // invoke user Worker
    return await customerScript.fetch(request);
  },
};

Update the wrangler.toml file for dispatch-worker and add the dispatch namespace binding:

# ... other content above ...

[[dispatch_namespaces]]
binding = "DISPATCH_NAMESPACE"
namespace = "my-namespace"
outbound = { service = "outbound-worker", parameters = ["paramCustomerName"] }

3. Create an Outbound Worker

npm

npm create cloudflare@latest -- outbound-worker

yarn

yarn create cloudflare@latest outbound-worker

pnpm

pnpm create cloudflare@latest outbound-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 the newly created directory:

cd outbound-worker

Update the src/index.js file for outbound-worker:

export default {
  async fetch(request, env) {
    const { paramCustomerName } = env;
    // use the parameters passed by the dispatcher to know what this user this request is for
    // and return custom content back to the user worker
    return new Response(
      `intercepted a request for ${paramCustomerName} by the outbound`,
    );
  },
};

4. Start local dev session for your Workers

In separate terminals, start a local dev session for each of your Workers.

For your dispatcher Worker:

cd dispatch-worker
npx wrangler@dispatch-namespaces-dev dev --port 8600

For your outbound Worker:

cd outbound-worker
npx wrangler@dispatch-namespaces-dev dev --port 8601

And for your user Worker:

cd customer-worker-1
npx wrangler@dispatch-namespaces-dev dev --port 8602

5. Test your requests

Send a request to your dispatcher Worker:

curl http://localhost:8600

# -> user worker got "intercepted a request for customer-1 by the outbound" from fetch