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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.toml file as follows:

wrangler.toml
name = "my-worker"
[[queues.producers]]
queue = "my-queue"
binding = "YOUR_QUEUE"
[durable_objects]
bindings = [
{ name = "YOUR_DO_CLASS", class_name = "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.

src/worker.ts
interface Env {
YOUR_QUEUE: Queue;
YOUR_DO_CLASS: DurableObject;
}
export default {
async fetch(req: Request, env: Environment): 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;
}
}
}
export class YourDurableObject implements Durable Object {
constructor(public state: DurableObjectState, env: Env) {
this.state = state;
// Ensure you pass your bindings and environment variables into
// each Durable Object when it is initialized
this.env = env;
}
}
async fetch(request: Request) {
// Error handling elided for brevity.
// Publish to your queue
await this.env.YOUR_QUEUE.send({
id: this.state.id // Write the ID of the Durable Object to your queue
// Write any other properties to your queue
});
return new Response("wrote to queue")
}