Durable Objects spiegati
Comprenda i Durable Objects per applicazioni serverless stateful, mantenendo uno stato coerente a livello globale.
Durable Objects spiegati è una lezione Edge Computing with Cloudflare Workers & Deno gratuita su CoddyKit. Questa è la lezione 2 di 4. Puoi leggere la lezione completa qui gratuitamente — poi esercitati direttamente nel browser con un editor di codice integrato e un tutor IA disponibile 24/7. Fa parte del percorso di apprendimento Edge Computing with Cloudflare Workers & Deno, e i tuoi progressi si sincronizzano tra il web e l'app CoddyKit. Il corso Edge Computing with Cloudflare Workers & Deno include 4 lezioni in totale.
Parti di questa lezione non sono ancora state tradotte e vengono mostrate in inglese.
The State Problem at the Edge
Serverless functions, like Cloudflare Workers, are typically stateless. This means each request is processed independently, without remembering past interactions.
While great for scalability and cost-efficiency, what if you need to maintain a consistent piece of information across multiple requests or users globally? Think about a live chat room, a game lobby, or a shared counter.
Introducing Durable Objects
Cloudflare Durable Objects solve this fundamental challenge. They are a powerful primitive for building stateful serverless applications directly at the edge.
- They provide a single-instance, globally consistent object.
- Each Durable Object instance has a unique ID and its own private storage.
- They act like tiny, persistent servers that live at the edge.
Unique IDs & Global Consistency
The core concept behind Durable Objects is their unique identity. When you create or retrieve a Durable Object using a specific ID, Cloudflare ensures that only one instance of that object exists and runs globally.
No matter where a request originates from (e.g., Tokyo, New York, London), if it targets the same Durable Object ID, it will be routed to that single, consistent instance. This eliminates the need for complex distributed synchronization.
Anatomy of a Durable Object
A Durable Object is defined as a standard JavaScript class. It must have:
- A
constructor(state, env)method, wherestateprovides access to its storage andenvholds environment variables. - An
async fetch(request)method, which processes incoming HTTP requests, similar to a regular Worker.
It's essentially a self-contained, stateful mini-Worker.
Persistent Storage with state.storage
Each Durable Object instance has its own private, durable key-value storage, accessible via this.state.storage. This allows the object to persist data across invocations and even across restarts.
await this.state.storage.put('key', value): Stores data.await this.state.storage.get('key'): Retrieves data.await this.state.storage.delete('key'): Removes data.
Values can be any JSON-serializable type, making it versatile for various data needs.
Code: Counter Worker & DO
This example shows a Cloudflare Worker interacting with a simple Counter Durable Object. The DO maintains a count that persists across requests and is globally consistent.
To run this, you'd define the Counter Durable Object binding in your wrangler.toml file.
export class Counter {
constructor(state, env) {
this.state = state;
this.env = env;
}
async fetch(request) {
let url = new URL(request.url);
// Retrieve current count from storage, default to 0
let currentCount = (await this.state.storage.get("value")) || 0;
if (url.pathname === "/increment") {
currentCount++;
await this.state.storage.put("value", currentCount);
return new Response(`Count: ${currentCount}`);
} else if (url.pathname === "/decrement") {
currentCount--;
await this.state.storage.put("value", currentCount);
return new Response(`Count: ${currentCount}`);
} else if (url.pathname === "/get") {
return new Response(`Count: ${currentCount}`);
}
return new Response("Not found", { status: 404 });
}
}
export default {
async fetch(request, env) {
// Get a unique Durable Object ID based on a name
// 'COUNTER' is the binding name configured in wrangler.toml
let id = env.COUNTER.idFromName("global-counter");
// Get a 'stub' (a proxy) to interact with the Durable Object
let stub = env.COUNTER.get(id);
// Forward the incoming request to the Durable Object's fetch method
return stub.fetch(request);
}
};How the Counter Code Works
1. The Counter class defines the Durable Object's behavior, handling /increment, /decrement, and /get routes and persisting its value.
2. The main Worker's fetch handler:
- It uses
env.COUNTER.idFromName("global-counter")to obtain a deterministic ID for our counter. env.COUNTER.get(id)returns a stub, which is a network proxy to the Durable Object.stub.fetch(request)forwards the original request to the Durable Object instance, allowing it to process the request and update its state.
Global Consistency in Action
Imagine users from different locations (e.g., Europe, Asia, Americas) all interacting with the /increment endpoint of your Worker. Because they all target the "global-counter" ID, Cloudflare guarantees they will all interact with the exact same instance of the Counter Durable Object.
This ensures that the count is always consistent, regardless of the user's location, simplifying complex distributed state management that would otherwise be very challenging.
Common Use Cases for DOs
Durable Objects are ideal for scenarios requiring strong consistency and shared, mutable state at the edge:
- Real-time Collaboration: Shared whiteboards, document editing.
- Gaming: Game lobbies, player state, matchmaking.
- Live Chat: Chat rooms, message queues for real-time communication.
- Stateful APIs: Managing user sessions, shopping carts, or unique resource locks.
They bring traditional stateful patterns to the serverless edge, making complex applications simpler to build.
Quick Check: Durable Objects
Which of the following best describes the primary benefit of Cloudflare Durable Objects?
Recap: Durable Objects Explained
In this lesson, we explored Cloudflare Durable Objects, a powerful tool for stateful serverless applications.
- They provide globally consistent, single-instance state at the edge.
- Each DO has a unique ID and private, durable storage (
state.storage). - Workers interact with DOs by obtaining stubs and forwarding requests.
- They are ideal for real-time, collaborative, and stateful applications that demand strong consistency.
Durable Objects bridge the gap between stateless serverless and traditional stateful services, simplifying complex distributed systems.
Domande Frequenti
La lezione «Durable Objects spiegati» è gratuita?
Sì — il testo completo di «Durable Objects spiegati» è gratuito qui sul web. Per esercitarvi in modo interattivo (un editor di codice integrato e un tutor IA 24/7) e sbloccare il resto del corso Edge Computing with Cloudflare Workers & Deno, passa a CoddyKit PRO. Il corso Edge Computing with Cloudflare Workers & Deno include 4 lezioni in totale.
Cosa imparerò in «Durable Objects spiegati»?
Comprenda i Durable Objects per applicazioni serverless stateful, mantenendo uno stato coerente a livello globale. Eserciti Edge Computing with Cloudflare Workers & Deno con codice pratico che esegui direttamente nel browser, e un tutor IA 24/7 risponde alle tue domande mentre lavori sulla lezione.
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Tutte le lezioni di questo corso
- Cloudflare KV Store
- Durable Objects spiegati
- Integrazione di Deno con lo storage edge
- Eseguire query con D1 SQL all’edge