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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_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.

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) {
      // Create (or get) a Durable Object based on that userId.
      let durableObjectId = env.YOUR_DO_CLASS.idFromName(userIdParam);
      // Get a "stub" that allows you to call that Durable Object
      let durableObjectStub = env.YOUR_DO_CLASS.get(durableObjectId);


      // 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")
  }