resonate-durable-sleep-scheduled-work-typescript

Resonate Durable Sleep & Scheduled Work (TypeScript)

Overview

Resonate's ctx.sleep() creates suspension points where workflows pause without consuming resources. Unlike regular setTimeout() or sleep(), durable sleep survives crashes, restarts, and redeployments. The workflow suspends its state, and Resonate resumes it exactly where it left off after the delay expires.

Core principle: yield* ctx.sleep(milliseconds) suspends execution durably. Workflows can sleep for seconds, hours, days, or weeks without holding threads, connections, or memory.

Mental Model

Regular Sleep (Ephemeral):
  Process → sleep(10h) → [BLOCKS THREAD] → Resume
  Crash during sleep? → LOST, never resumes

Durable Sleep (Resonate):
  Workflow → yield* ctx.sleep(10h) → [SUSPENDS STATE] → Resume
  Crash during sleep? → Automatically resumes after delay
  Restart process? → Resumes from checkpoint after delay

No resources held during sleep - workflow exists only as durable state.

Basic Pattern: Simple Countdown

import { Context } from "@resonatehq/sdk";

function* countdown(
  ctx: Context,
  count: number,
  delayMinutes: number,
  notificationUrl: string
) {
  for (let i = count; i > 0; i--) {
    // Send notification
    yield* ctx.run(sendNotification, notificationUrl, `Countdown: ${i}`);

    // Durable sleep - workflow suspends here
    yield* ctx.sleep(delayMinutes * 60 * 1000);
  }

  // Send final notification
  yield* ctx.run(sendNotification, notificationUrl, "Done!");
}

async function sendNotification(
  _ctx: Context,
  url: string,
  message: string
) {
  await fetch(url, {
    method: "POST",
    body: message,
    headers: { "Content-Type": "text/plain" }
  });
}

Usage:

// Count down from 5, waiting 1 minute between each count
await resonate.run(
  "countdown-1",
  countdown,
  5,              // count
  1,              // delay in minutes
  "https://ntfy.sh/mychannel"
);

What happens:

1. Sends "Countdown: 5"
2. Sleeps 1 minute (workflow suspends, no resources held)
3. Resumes, sends "Countdown: 4"
4. Sleeps 1 minute
5. Repeats until "Done!"