Durable Object Namespace

Description

A Durable Object namespace is a set of Durable Objects that are backed by the same Durable Object class. There is only one Durable Object namespace per class. A Durable Object namespace can contain any number of Durable Objects.

The DurableObjectNamespace interface is used to obtain a reference to new or existing Durable Objects. The interface is accessible from the fetch handler on a Cloudflare Worker via the env parameter, which is the standard interface when referencing bindings declared in the wrangler.toml / wrangler.json file.

This interface defines several methods that can be used to create an ID for a Durable Object. Note that creating an ID for a Durable Object does not create the Durable Object. The Durable Object is created lazily after calling DurableObjectNamespace::get to create a DurableObjectStub from a DurableObjectId. This ensures that objects are not constructed until they are actually accessed.

JavaScript

import { DurableObject } from "cloudflare:workers";

// Durable Object
export class MyDurableObject extends DurableObject {
  ...
}

// Worker
export default {
  async fetch(request, env) {
    // Every unique ID refers to an individual instance of the Durable Object class
    const id = env.MY_DURABLE_OBJECT.idFromName("foo");

    // A stub is a client Object used to invoke methods defined by the Durable Object
    const stub = env.MY_DURABLE_OBJECT.get(id);
    ...
  }
}

TypeScript

import { DurableObject } from "cloudflare:workers";

export interface Env {
  MY_DURABLE_OBJECT: DurableObjectNamespace<MyDurableObject>;
}

// Durable Object
export class MyDurableObject extends DurableObject {
  ...
}

// Worker
export default {
  async fetch(request, env) {
    // Every unique ID refers to an individual instance of the Durable Object class
    const id = env.MY_DURABLE_OBJECT.idFromName("foo");

    // A stub is a client Object used to invoke methods defined by the Durable Object
    const stub = env.MY_DURABLE_OBJECT.get(id);
    ...
  }
} satisfies ExportedHandler<Env>;

Methods

idFromName

idFromName creates a unique DurableObjectId which refers to an individual instance of the Durable Object class. Named Durable Objects are the most common method of referring to Durable Objects.

const fooId = env.MY_DURABLE_OBJECT.idFromName("foo");
const barId = env.MY_DURABLE_OBJECT.idFromName("bar");

Parameters

• A required string to be used to generate a DurableObjectId corresponding to the name of a Durable Object.

Return values

• A DurableObjectId referring to an instance of a Durable Object class.

newUniqueId

newUniqueId creates a randomly generated and unique DurableObjectId which refers to an individual instance of the Durable Object class. IDs created using newUniqueId, will need to be stored as a string in order to refer to the same Durable Object again in the future. For example, the ID can be stored in Workers KV, another Durable Object, or in a cookie in the user's browser.

const id = env.MY_DURABLE_OBJECT.newUniqueId();
const euId = env.MY_DURABLE_OBJECT.newUniqueId({ jurisdiction: "eu" });

newUniqueId results in lower request latency at first use

The first time you get a Durable Object stub based on an ID derived from a name, the system has to take into account the possibility that a Worker on the opposite side of the world could have coincidentally accessed the same named Durable Object at the same time. To guarantee that only one instance of the Durable Object is created, the system must check that the Durable Object has not been created anywhere else. Due to the inherent limit of the speed of light, this round-the-world check can take up to a few hundred milliseconds. newUniqueId can skip this check.

After this first use, the location of the Durable Object will be cached around the world so that subsequent lookups are faster.

Parameters

• An optional object with the key jurisdiction and value of a jurisdiction string.

Return values

• A DurableObjectId referring to an instance of the Durable Object class.

idFromString

idFromString creates a DurableObjectId from a previously generated ID that has been converted to a string. This method throws an exception if the ID is invalid, for example, if the ID was not created from the same DurableObjectNamespace.

// Create a new unique ID
const id = env.MY_DURABLE_OBJECT.newUniqueId();
// Convert the ID to a string to be saved elsewhere, e.g. a session cookie
const session_id = id.toString();

...
// Recreate the ID from the string
const id = env.MY_DURABLE_OBJECT.idFromString(session_id);

Parameters

• A required string corresponding to a DurableObjectId previously generated either by newUniqueId or idFromName.

Return values

• A DurableObjectId referring to an instance of a Durable Object class.

get

get obtains a DurableObjectStub from a DurableObjectId which can be used to invoke methods on a Durable Object.

This method returns the stub immediately, often before a connection has been established to the Durable Object. This allows requests to be sent to the instance right away, without waiting for a network round trip.

const id = env.MY_DURABLE_OBJECT.newUniqueId();
const stub = env.MY_DURABLE_OBJECT.get(id);

Parameters

• A required DurableObjectId
• An optional object with the key locationHint and value of a locationHint string.

Return values

• A DurableObjectStub referring to an instance of a Durable Object class.

jurisdiction

jurisdiction creates a subnamespace from a namespace where all Durable Object IDs and references created from that subnamespace will be restricted to the specified jurisdiction.

const subnamespace = env.MY_DURABLE_OBJECT.jurisdiction("foo");
const euId = subnamespace.idFromName("foo");

Parameters

• A required jurisdiction string.

Return values

• A DurableObjectNamespace scoped to a particular geographic jurisdiction.

Related resources

• Durable Objects: Easy, Fast, Correct – Choose Three ↗.

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