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Local development

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

​​ 1. Create a user worker

$ npm create cloudflare@latest customer-worker-1

When following the interactive prompts, answer the questions as below:

  • Select no to using TypeScript.
  • Select no to deploying your application.

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

src/index.js
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:

wrangler.toml
# ... other content above ...
dispatch_namespace = "my-namespace"

​​ 2. Create a dispatch worker

$ npm create cloudflare@latest dispatch-worker

When following the interactive prompts, answer the questions as below:

  • Select no to using TypeScript.
  • Select no to deploying your application.

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

src/index.js
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:

wrangler.toml
# ... other content above ...
[[dispatch_namespaces]]
binding = "DISPATCH_NAMESPACE"
namespace = "my-namespace"
outbound = { service = "outbound-worker", parameters = ["paramCustomerName"] }

​​ 3. Create an Outbound Worker

$ npm create cloudflare@latest outbound-worker

When following the interactive prompts, answer the questions as below:

  • Select no to using TypeScript.
  • Select no to deploying your application.

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

src/index.js
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