Resonate Countdown on Supabase Edge Functions

A Countdown powered by the Resonate Typescript SDK and Supabase Edge Functions. 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 Supabase Edge Function execution. After the specified delay, Resonate will resume (restart) the countdown function by triggering a new Supabase Edge Function 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 Supabase Edge Function 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 Supabase CLI or you can deploy the Countdown to Supabase 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

Install the Supabase CLI

1.2. Start Supabase locally

supabase start

1.3. Setup the Countdown

Clone the repository

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

Install dependencies

npm install

1.4. Serve the Countdown function

supabase functions serve countdown

1.5 Start the resonate server

resonate dev --system-url http://host.docker.internal:8001

1.6. 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://127.0.0.1:54321/functions/v1/countdown

1.7. 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 Supabase

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

2.1 Prerequisites

Resonate

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

brew install resonatehq/tap/resonate

Supabase

Install the Supabase CLI

2.1 Deploy your function

supabase functions deploy countdown --project-ref <PROJECT_ID>

2.2 Start the resonate server behind ngrok

ngrok http 8001

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

Example

resonate dev --system-url  https://583ef7749990.ngrok-free.app

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 $FUNCTION_URL

Example

resonate invoke countdown.1 --func countdown --arg 5 --arg 1 --arg https://ntfy.sh/resonatehq-17905 --target https://<orgID>.supabase.co/functions/v1/countdown

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.