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Use Queues from Durable Objects

Publish to a queue from within a Durable Object.

The following example shows you how to write a Worker script to publish to Cloudflare Queues from within a Durable Object.

Prerequisites:

Configure your Wrangler file as follows:

{
  "name": "my-worker",
  "queues": {
    "producers": [
      {
        "queue": "my-queue",
        "binding": "YOUR_QUEUE"
      }
    ]
  },
  "durable_objects": {
    "bindings": [
      {
        "name": "YOUR_DO_CLASS",
        "class_name": "YourDurableObject"
      }
    ]
  },
  "migrations": [
    {
      "tag": "v1",
      "new_sqlite_classes": [
        "YourDurableObject"
      ]
    }
  ]
}

The following Worker script:

  1. Creates a Durable Object stub, or retrieves an existing one based on a userId.
  2. Passes request data to the Durable Object.
  3. Publishes to a queue from within the Durable Object.

The constructor() in the Durable Object makes your Environment available (in scope) on this.env to the fetch() handler in the Durable Object.

TypeScript
interface Env {
  YOUR_QUEUE: Queue;
  YOUR_DO_CLASS: DurableObjectNamespace;
}


export default {
  async fetch(req, env): Promise<Response> {
    // Assume each Durable Object is mapped to a userId in a query parameter
    // In a production application, this will be a userId defined by your application
    // that you validate (and/or authenticate) first.
    let url = new URL(req.url)
    let userIdParam = url.searchParams.get("userId")


    if (userIdParam) {
      // Get a stub that allows you to call that Durable Object
      let durableObjectStub = env.YOUR_DO_CLASS.getByName(userIdParam);


      // Pass the request to that Durable Object and await the response
      // This invokes the constructor once on your Durable Object class (defined further down)
      // on the first initialization, and the fetch method on each request.
      // We pass the original Request to the Durable Object's fetch method
      let response = await durableObjectStub.fetch(req);


      // This would return "wrote to queue", but you could return any response.
      return response;
    }
    return new Response("userId must be provided", { status: 400 });
  },
} satisfies ExportedHandler<Env>;


export class YourDurableObject implements DurableObject {
  constructor(private state: DurableObjectState, private env: Env) {}


  async fetch(req: Request): Promise<Response> {
    // Error handling elided for brevity.
    // Publish to your queue
    await this.env.YOUR_QUEUE.send({
      id: this.state.id.toString() // Write the ID of the Durable Object to your queue
      // Write any other properties to your queue
    });


    return new Response("wrote to queue")
  }