Countdown webhooks

The same job, two ways

// Polling: one request per timer per interval, and you find out
// somewhere between 0 and 60 seconds late.
setInterval(async () => {
  for (const timerId of activeTimers) {          // 500 timers
    const { data } = await call(`/timers/${timerId}/status`);
    if (data.ended) await releaseReservation(timerId);
  }
}, 60_000);                                       // = 720,000 requests/day

// Webhooks: one request when it actually happens.
app.post("/webhooks/countdownshare", async (req, res) => {
  res.sendStatus(200);                            // acknowledge first
  await queue.add("release-reservation", req.body);
});

How they relate

  Destination                 Rule                      Delivery
  (account-level)             (per timer)               (per firing)

  "my order service"   <----  "1 hour left"      ---->  attempt 1: 500
   https://…/hooks           on timer A                attempt 2: 200 OK
   whsec_…                                             status: succeeded
        ^
        |               <----  "ended"           ---->  attempt 1: 200 OK
        |                     on timer A                status: succeeded
        |
        +-------------  <----  "ended"           ---->  …
                              on timer B

  One destination. Many rules across many timers.

Register, attach, test

// 1. Register the destination once. Keep the signing secret —
//    it is returned here and never again.
const { data: destination } = await call("/webhook-destinations", {
  method: "POST",
  body: JSON.stringify({
    name: "Order automation",
    url: "https://example.com/webhooks/countdownshare",
  }),
});

await secrets.store("COUNTDOWNSHARE_WEBHOOK_SECRET", destination.signing_secret);

// 2. Attach a rule to the timer you care about.
await call(`/timers/${timerId}/webhook-rules`, {
  method: "POST",
  body: JSON.stringify({
    name: "Reservation expired",
    webhook_destination_id: destination.id,
    condition: { field: "status", operator: "equals", value: "ended" },
    delivery: "once",
  }),
});

// 3. Confirm the plumbing before you rely on it.
await call(`/webhook-destinations/${destination.id}/test`, { method: "POST" });