---
title: "How do I send a daily summary on a cron schedule?"
description: "Declare a UTC cron, accumulate values in KV, post a summary once per day"
---

> Documentation Index
> Fetch the complete documentation index at: https://docs.devicesdk.com/llms.txt
> Use this file to discover all available pages before exploring further.

# How do I send a daily summary on a cron schedule?

A common pattern for environmental devices: sample frequently, aggregate, send once per day.

## `devicesdk.ts`

```typescript
import { defineConfig } from "@devicesdk/cli";

export default defineConfig({
  projectId: "daily-summary",
  devices: {
main: {
  className: "DailySummary",
  main: "./src/devices/main.ts",
  deviceType: "pico-w",
  wifi: { ssid: "YOUR_WIFI_SSID", password: "YOUR_WIFI_PASSWORD" },
},
  },
});
```

Then set the webhook URL once:

```bash
devicesdk env set SUMMARY_WEBHOOK_URL=https://discord.com/api/webhooks/...
```

## `src/devices/main.ts`

```typescript
import { DeviceEntrypoint, type DeviceResponse } from "@devicesdk/core";

interface Window {
  startedAt: number;
  count: number;
  sumC: number;
  minC: number;
  maxC: number;
}

const FRESH: Window = {
  startedAt: 0,
  count: 0,
  sumC: 0,
  minC: Number.POSITIVE_INFINITY,
  maxC: Number.NEGATIVE_INFINITY,
};

export class DailySummary extends DeviceEntrypoint {
  crons = {
sample: "*/15 * * * *", // every 15 min UTC - collect a reading
summary: "0 8 * * *",    // every day at 08:00 UTC - post the summary
  };

  async onCron(name: string) {
if (name === "sample") {
  await this.env.DEVICE.getTemperature();
} else if (name === "summary") {
  await this.postSummary();
}
  }

  async onMessage(message: DeviceResponse) {
if (message.type !== "temperature_result") return;
const w = (await this.env.DEVICE.kv.get<Window>("window")) ?? {
  ...FRESH,
  startedAt: Date.now(),
};
const c = message.payload.celsius;
const next: Window = {
  startedAt: w.startedAt || Date.now(),
  count: w.count + 1,
  sumC: w.sumC + c,
  minC: Math.min(w.minC, c),
  maxC: Math.max(w.maxC, c),
};
await this.env.DEVICE.kv.put("window", next);
  }

  private async postSummary() {
const w = await this.env.DEVICE.kv.get<Window>("window");
if (!w || w.count === 0) {
  console.log("No samples in window - skipping summary.");
  return;
}
const url = await this.env.VARS.get("SUMMARY_WEBHOOK_URL");
if (!url) {
  console.error("SUMMARY_WEBHOOK_URL not set - run `devicesdk env set`.");
  return;
}

const avg = (w.sumC / w.count).toFixed(1);
const body = JSON.stringify({
  content: `📊 Daily summary: ${w.count} samples, avg ${avg}°C (min ${w.minC.toFixed(1)}, max ${w.maxC.toFixed(1)})`,
});

const res = await fetch(url, {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body,
});
if (!res.ok) {
  console.error(`Webhook POST failed: ${res.status} ${res.statusText}`);
  return;
}

// Reset the window for the next day.
await this.env.DEVICE.kv.put("window", { ...FRESH, startedAt: Date.now() });
  }
}
```

## What this demonstrates

- Multiple named crons in one device.
- Accumulating state in KV across many invocations (the runtime is stateless - your class instance does *not* persist between events).
- Posting to an external webhook with a properly-handled non-2xx response.
- Resetting the aggregation window after a successful post.

## Notes

- Crons fire in UTC. Pick a time that lines up with your timezone - `0 8 * * *` is 08:00 UTC, which is 09:00 BST or 03:00 CDT.
- If the webhook is down at 08:00, the script logs the failure and **doesn't reset the window**. The next day's run will include yesterday's samples too - consider whether that matches your intent.
- For multiple devices contributing to one summary, see the [two-device RPC recipe](../two-devices-rpc/).

Source: https://docs.devicesdk.com/recipes/daily-cron-summary/index.mdx