---
title: Use the Alarms API
description: Use the Durable Objects Alarms API to batch requests to a Durable Object.
image: https://developers.cloudflare.com/dev-products-preview.png
---

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# Use the Alarms API

Use the Durable Objects Alarms API to batch requests to a Durable Object.

This example implements an `alarm()` handler that allows batching of requests to a single Durable Object.

When a request is received and no alarm is set, it sets an alarm for 10 seconds in the future. The `alarm()` handler processes all requests received within that 10-second window.

If no new requests are received, no further alarms will be set until the next request arrives.

* [  JavaScript ](#tab-panel-8653)
* [  Python ](#tab-panel-8654)

JavaScript

```
import { DurableObject } from "cloudflare:workers";
// Workerexport default {  async fetch(request, env) {    return await env.BATCHER.getByName("foo").fetch(request);  },};
// Durable Objectexport class Batcher extends DurableObject {  constructor(ctx, env) {    super(ctx, env);    this.storage = ctx.storage;    this.ctx.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() + 1000 * 10);    }
    // 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;  }}
```

Python

```
from workers import DurableObject, Response, WorkerEntrypoint, fetchimport time
# Workerclass Default(WorkerEntrypoint):  async def fetch(self, request):    stub = self.env.BATCHER.getByName("foo")    return await stub.fetch(request)
# Durable Objectclass Batcher(DurableObject):  def __init__(self, ctx, env):    super().__init__(ctx, env)    self.storage = ctx.storage
    @self.ctx.blockConcurrencyWhile    async def initialize():      vals = await self.storage.list(reverse=True, limit=1)      self.count = 0      if len(vals) > 0:          self.count = int(vals.keys().next().value)
  async def fetch(self, request):    self.count += 1
    # 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.    current_alarm = await self.storage.getAlarm()    if current_alarm is None:      self.storage.setAlarm(int(time.time() * 1000) + 1000 * 10)
    # Add the request to the batch.    await self.storage.put(self.count, await request.text())    return Response.json(      {"queued": self.count}    )
  async def alarm(self):    vals = await self.storage.list()    await fetch(      "http://example.com/some-upstream-service",      method="POST",      body=list(vals.values())    )    await self.storage.deleteAll()    self.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.

Finally, configure your Wrangler file to include a Durable Object [binding](https://developers.cloudflare.com/durable-objects/get-started/#4-configure-durable-object-bindings) and [migration](https://developers.cloudflare.com/durable-objects/reference/durable-objects-migrations/) based on the namespace and class name chosen previously.

* [  wrangler.jsonc ](#tab-panel-8655)
* [  wrangler.toml ](#tab-panel-8656)

JSONC

```
{  "$schema": "./node_modules/wrangler/config-schema.json",  "name": "durable-object-alarm",  "main": "src/index.ts",  "durable_objects": {    "bindings": [      {        "name": "BATCHER",        "class_name": "Batcher"      }    ]  },  "migrations": [    {      "tag": "v1",      "new_sqlite_classes": [        "Batcher"      ]    }  ]}
```

TOML

```
"$schema" = "./node_modules/wrangler/config-schema.json"name = "durable-object-alarm"main = "src/index.ts"
[[durable_objects.bindings]]name = "BATCHER"class_name = "Batcher"
[[migrations]]tag = "v1"new_sqlite_classes = [ "Batcher" ]
```

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