Outbound Workers

Outbound Workers sit between your customer’s Workers and the public Internet. They give you visibility into all outgoing fetch() requests from User Workers.

​​ General Use Cases

Outbound Workers can be used to:

• Log all subrequests to identify malicious hosts or usage patterns.
• Create, allow, or block lists for hostnames requested by user Workers.
• Configure authentication to your APIs behind the scenes (without end developers needing to set credentials).

​​ Use Outbound Workers

To use Outbound Workers:

1. Create a Worker intended to serve as your Outbound Worker.
2. Outbound Worker can be specified as an optional parameter in the dispatch namespaces binding in a projects wrangler.toml. Optionally, to pass data from your Dispatch Worker to the Outbound Worker, the variable names must be specified under parameters.

Make sure that you have wrangler@3.3.0 or later installed.

wrangler.toml
[[dispatch_namespaces]]
binding = "dispatcher"
namespace = "<NAMESPACE_NAME>"
outbound = {service = "<SERVICE_NAME>", parameters = [customer_name,url]}

3. Edit your Dispatch Worker to call the Outbound Worker and declare variables to pass on dispatcher.get().

index.js
export default {
 async fetch(request, env) {
   try {
     // parse the URL, read the subdomain
     let workerName = new URL(request.url).host.split('.')[0];
     let userWorker = env.dispatcher.get(
       workerName,
       {},
       {// outbound arguments
         outbound: {
          customer_name: workerName,
            url: request.url}
          }
       }
     );
     return await userWorker.fetch(request);
   } catch (e) {
     if (e.message.startsWith('Worker not found')) {
       // we tried to get a worker that doesn't exist in our dispatch namespace
       return new Response('', { status: 404 });
     }
      return new Response(e.message, { status: 500 });
   }
 },
};

4. The Outbound Worker will now be invoked on any fetch() requests from user Workers. The User Worker will trigger a FetchEvent on the Outbound Worker. The variables declared in the binding can be accessed in the Outbound Worker through env.<VAR_NAME>.