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Countdown — Resonate example

Resonate Countdown

A Countdown powered by the Resonate TypeScript SDK. The countdown sends notifications to ntfy.sh, a simple HTTP-based notification service, at configurable intervals.

Countdown Workflow

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, and after the specified delay, Resonate will resume the countdown function.

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
		yield* ctx.sleep(delay * 60 * 1000);
	}
	// send the last notification to ntfy.sh
	yield* ctx.run(notify, url, `Done`);
}

Try yourself: Between notifications, kill the worker and restart. The countdown won't be affected and picks up exactly where it left off.

Countdown Workflow

Setup Dependencies:

1 Setup the Resonate Server

Install the Resonate Server

brew install resonatehq/tap/resonate

2 Setup the countdown

Clone the repository

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

Install dependencies

npm install

Running the Project

1. Start the Resonate Server

In Terminal #1, start the Resonate server in development mode listening on http://localhost:8001.

resonate dev
  • When you start the server in development mode, the server does not persist data on disk and will lose its state when you stop the process

2. Start the Worker

In Terminal #2, start the Resonate worker:

npm start

3. Invoke a Countdown

In Terminal #3, start the countdown, for example, counting down from 5, every minute, and posting notifications to https://ntfy.sh/resonatehq:

resonate invoke countdown.1 --func countdown --arg 5 --arg 1 --arg https://ntfy.sh/resonatehq

Parameters:

  • countdown.1: Unique ID for this countdown
  • --arg 5: Count down from 5
  • --arg 1: Wait 1 minute between counts
  • --arg https://ntfy.sh/resonatehq: Where to send notifications

Open https://ntfy.sh/resonatehq in your browser to see the notifications in real-time.

Checking Progress

Get details of a specific countdown:

resonate promises get countdown.1

View all promises:

resonate promises search --tags '{"resonate:origin":"countdown.1"}'

Learn More