Resonate Countdown on Cloudflare Workers

A Countdown powered by the Resonate Typescript SDK and Cloudflare Workers. The countdown sends periodic notifications to ntfy.sh at configurable intervals.

Behind the Scenes

The Countdown is implemented with Resonate's Durable Execution framework, Distributed Async Await. The Countdown is a simple loop that can sleep for hours, days, or weeks. On yield ctx.sleep the countdown function suspends (terminates), immediately completing the Cloudflare Worker execution. After the specified delay, Resonate will resume (restart) the countdown function by triggering a new Cloudflare Worker execution.

export function* countdown(
	ctx: Context,
	count: number,
	delay: number,
	url: string,
) {
	for (let i = count; i > 0; i--) {
		// send notification to ntfy.sh
		yield* ctx.run(notify, url, `Countdown: ${i}`);
		// sleep creates a suspension point causing
		// the Cloudflare Worker execution to terminate
		yield* ctx.sleep(delay * 60 * 1000);
	}
	// send the last notification to ntfy.sh
	yield* ctx.run(notify, url, `Done`);
}

Key Concepts:

• Suspension and Resumption: Executions can be suspended for any amount of time
• Stateful executions on stateless infrastructure: Short-lived function instances executing one step of a long-lived execution coordinated by the Resonate Server.

---

Running the Example

You can run the Countdown locally on your machine with Cloudflares's Wrangler Framework or you can deploy the Countdown to Cloudflare Platform.

1. Running Locally

1.1. Prerequisites

Install the Resonate Server & CLI with Homebrew or download the latest release from Github.

brew install resonatehq/tap/resonate

1.2. Start Resonate Server

Start the Resonate Server. By default, the Resonate Server will listen at http://localhost:8001.

resonate dev

1.3. Setup the Countdown

Clone the repository

git clone https://github.com/resonatehq-examples/example-countdown-cloudflare-ts
cd example-countdown-cloudflare-ts

Install dependencies

npm install

1.4. Start the Countdown

Start the Cloudflare Worker. By default, the Cloudflare Worker will listen at http://localhost:8787.

npm run dev

1.5. Invoke the Countdown

The examples use ntfy.sh to send notifications. Create a unique channel name (to avoid receiving notifications from other users) and open the ntfy.sh channel in your browser.

echo https://ntfy.sh/resonatehq-$RANDOM

Start a countdown

resonate invoke <promise-id> --func countdown --arg <count> --arg <delay-in-minutes> --arg https://ntfy.sh/<channel> --target <function-url>

Example

resonate invoke countdown.1 --func countdown --arg 5 --arg 1 --arg https://ntfy.sh/resonatehq-17905 --target http://localhost:8787

1.6. Inspect the execution

Use the resonate tree command to visualize the countdown execution.

resonate tree countdown.1

Example output (while waiting on the second sleep):

countdown.1
├── countdown.1.0 🟢 (run)
├── countdown.1.1 🟢 (sleep)
├── countdown.1.2 🟢 (run)
└── countdown.1.3 🟡 (sleep)

2. Deploying to Cloudflare

This section guides you through deploying the countdown example to Cloudflare Platform using Workers for the countdown function.

2.1 Prerequisites

Resonate

Install the Resonate CLI with Homebrew or download the latest release from Github.

brew install resonatehq/tap/resonate

Cloudflare Platform

Ensure you have a Cloudflare Platform account.

Warning

Cloudflare Platform offers extensive configuration options. The instructions in this guide provide a baseline setup that you will need to adapt for your specific requirements, organizational policies, or security constraints.

2.1 Create a Hello World Worker

2.2 Deploy the Resonate Server to Workers

Expose the Resonate server running locally to the cloud

Step 1: ngrok url

ngrok http 8001

Step 2: Run the server locally

Configure the Resonate Server with its URL.

resonate dev --system-url <ngrok-url>

Example

resonate dev --system-url https://3d6a08125e17.ngrok-free.app

2.3 Deploy the Countdown to Workers

Paste the wrangler.toml at the root of this directory (replace the name with the name of your newly created worker)

name = "XXXXX-XXXXX-XXXX"
main = "src/index.ts"
compatibility_date = "2024-01-01"

Deploy it

npm run deploy

2.4 Invoke the Countdown

The examples use ntfy.sh to send notifications. Create a unique channel name (to avoid receiving notifications from other users) and open the ntfy.sh channel in your browser.

echo https://ntfy.sh/resonatehq-$RANDOM

Start a countdown

resonate invoke <promise-id> --func countdown --arg <count> --arg <delay-in-minutes> --arg https://ntfy.sh/<channel> --target $WORKER_URL

Example

resonate invoke countdown.1 --func countdown --arg 5 --arg 1 --arg https://ntfy.sh/resonatehq-22012 --target $WORKER_URL

2.5. Inspect the execution

Use the resonate tree command to visualize the countdown execution.

resonate tree countdown.1

Example output (while waiting on the second sleep):

countdown.1
├── countdown.1.0 🟢 (run)
├── countdown.1.1 🟢 (sleep)
├── countdown.1.2 🟢 (run)
└── countdown.1.3 🟡 (sleep)

Troubleshooting

If everything is configured correctly, you will see notifications in your ntfy.sh workspace.

If you are still having trouble please open an issue.