Durable Objects

Per-id serialized state and alarms, backed by synchronous storage calls.

Configuration

"durable_objects": { "COUNTER": "Counter" }

Binding name maps to a class name declared in the same file as your handler.

Usage

class Counter {
  constructor(state, env) { this.state = state; this.env = env; }
  // Synchronous, like every other binding: state.storage.* are blocking calls.
  fetch(request) {
    const n = (this.state.storage.get("n") || 0) + 1;
    this.state.storage.put("n", n);
    // Debounced: a burst of requests produces one alarm, not one per request.
    this.state.storage.setAlarm(Date.now() + 1000);
    return Response.json({ n });
  }
  // Runs later, with no request in flight.
  alarm() {
    this.env.DB.prepare("INSERT INTO rollup (n) VALUES (?)").bind(this.state.storage.get("n")).run();
  }
}
export default {
  fetch(request) {
    const id = env.COUNTER.idFromName("global");
    return env.COUNTER.get(id).fetch(request);
  },
};

Semantics

Related

• D1 — for data that outlives a single object’s id