Use the Alarms API
Use the Durable Objects Alarms API to batch requests to a Durable Object.
This example implements an alarm()
handler that wakes the Durable Object once every 10 seconds to batch requests to a single Durable Object. The alarm()
handler will delay processing until there is enough work in the queue.
// Worker
export default { async fetch(request, env) { let id = env.BATCHER.idFromName("foo"); return await env.BATCHER.get(id).fetch(request); },
};
const SECONDS = 1000;
// Durable Object
export class Batcher { constructor(state, env) { this.state = state; this.storage = state.storage; this.state.blockConcurrencyWhile(async () => { let vals = await this.storage.list({ reverse: true, limit: 1 }); this.count = vals.size == 0 ? 0 : parseInt(vals.keys().next().value); }); }
async fetch(request) { this.count++;
// If there is no alarm currently set, set one for 10 seconds from now // Any further POSTs in the next 10 seconds will be part of this batch. let currentAlarm = await this.storage.getAlarm(); if (currentAlarm == null) { this.storage.setAlarm(Date.now() + 10 * SECONDS); }
// Add the request to the batch. await this.storage.put(this.count, await request.text()); return new Response(JSON.stringify({ queued: this.count }), { headers: { "content-type": "application/json;charset=UTF-8", }, }); }
async alarm() { let vals = await this.storage.list(); await fetch("http://example.com/some-upstream-service", { method: "POST", body: Array.from(vals.values()), }); await this.storage.deleteAll(); this.count = 0; }
}
The alarm()
handler will be called once every 10 seconds. If an unexpected error terminates the Durable Object, the alarm()
handler will be re-instantiated on another machine. Following a short delay, the alarm()
handler will run from the beginning on the other machine.