Use KV from Durable Objects
Read and write to/from KV within a Durable Object
The following Worker script shows you how to configure a Durable Object to read from and/or write to a Workers KV namespace. This is useful when using a Durable Object to coordinate between multiple clients, and allows you to serialize writes to KV and/or broadcast a single read from KV to hundreds or thousands of clients connected to a single Durable Object using WebSockets.
Prerequisites:
- A KV namespace created via the Cloudflare dashboard or the wrangler CLI.
- A configured binding for the
kv_namespace
in the Cloudflare dashboard orwrangler.toml
file. - A Durable Object namespace binding.
Configure your wrangler.toml
file as follows:
wrangler.tomlname = "my-worker"
kv_namespaces = [ { binding = "YOUR_KV_NAMESPACE", id = "<id_of_your_namespace>" }
]
[durable_objects]
bindings = [ { name = "YOUR_DO_CLASS", class_name = "YourDurableObject" }
]
src/index.tsinterface Env { YOUR_KV_NAMESPACE: KVNamespace; YOUR_DO_CLASS: DurableObjectNamespace;
}
export default { async fetch(req: Request, env: Env): Promise<Response> { // Assume each Durable Object is mapped to a roomId in a query parameter // In a production application, this will likely be a roomId defined by your application // that you validate (and/or authenticate) first. let url = new URL(req.url) let roomIdParam = url.searchParams.get("roomId")
if (roomIdParam) { // Create (or get) a Durable Object based on that roomId. let durableObjectId = env.YOUR_DO_CLASS.idFromName(roomIdParam); // 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. // // You could pass the original Request to the Durable Object's fetch method // or a simpler URL with just the roomId. let response = await durableObjectStub.fetch(`http://do/${roomId}`);
// This would return the value you read from KV *within* the Durable Object. return response; } }
}
export class YourDurableObject implements DurableObject { constructor(public state: DurableObjectState, env: Env) { this.state = state; // Ensure you pass your bindings and environmental variables into // each Durable Object when it is initialized this.env = env; } }
async fetch(request: Request) { // Error handling elided for brevity. // Write to KV await this.env.YOUR_KV_NAMESPACE.put("some-key");
// Fetch from KV let val = await this.env.YOUR_KV_NAMESPACE.get("some-other-key");
return Response.json(val) }