Piye cara ngimplementasikake graceful shutdown?

Question

Accepted Answer

**Graceful shutdown** tegese mandhegke server kanthi bersih nalika nampa signal terminasi — ngrampungake request sing lagi ngoncat, nutup koneksi (DB, lsp.), lan mbukak sumber daya — tinimbang matikke kanthi cepet lan ngilangi pekerjaan sing aktif. Iki penting banget kanggo zero-downtime deploys lan reliability.

## Kenapa abrupt shutdown dadi masalah

```text
Without graceful shutdown, when the process is killed (deploy, scale-down, crash):
  ✗ In-flight requests are dropped → users get errors
  ✗ DB transactions left incomplete
  ✗ Connections not closed cleanly → leaks/locks
```

Sejatining deploys lan autoscaling, proses dihentikake terus-terusan — menggawane kanthi bersih iku sing nggawe deployments lancar.

## Implementasine

```js
import http from "http";
const server = http.createServer(app);
server.listen(3000);

async function shutdown(signal) {
  console.log(`${signal} received — shutting down gracefully`);

// 1. Stop accepting NEW connections; finish existing ones
  server.close(async () => {
    // 2. This callback runs once all active requests have completed
    await db.end();            // close database pool
    await redis.quit();        // close other connections
    console.log("clean shutdown complete");
    process.exit(0);           // exit successfully
  });

// 3. Safety net: force-exit if cleanup hangs too long
  setTimeout(() => {
    console.error("forced shutdown — cleanup timed out");
    process.exit(1);
  }, 10_000).unref();
}

// Listen for termination signals
process.on("SIGTERM", () => shutdown("SIGTERM")); // sent by orchestrators (k8s, Docker)
process.on("SIGINT", () => shutdown("SIGINT"));   // Ctrl+C in dev
```

Urut-urutane: tangkep signal → `server.close()` (mandhegke koneksi anyar, nguras sing wis ana) → tutup DB/Redis/sumber daya liyane → metu. **Timeout fallback** meksa metu yen ana sing macet, supaya koneksi sing buntung ora bisa ngalangi mandhegke selamanya.

## Signame

```text
SIGTERM → the standard "please terminate" signal from orchestrators on deploy/scale-down
SIGINT  → Ctrl+C (development)
SIGKILL → cannot be caught (force kill) — graceful shutdown can't help here
```

## Ing lingkungan containerized

```text
Kubernetes/Docker send SIGTERM, wait a grace period (e.g. 30s), THEN SIGKILL.
Your app must finish within that window → keep the shutdown timeout shorter.
Readiness probes should mark the pod unready so the load balancer stops sending traffic.
```

## Kenapa iki penting

Graceful shutdown iku sing ngaktifake **zero-downtime deployments** lan operasi sing bisa dipercaya ing lingkungan modern (luwih-luwih containerized/orchestrated), ing ngendi proses dihentikake lan diulang terus.

Tanpa iku, saben deploy utawa scale-down ngilangi request aktif lan risiko inkonsistensi data.

Ngimplementasikake urut-urutane tangkep-signal → stop-accepting → drain → close-resources → exit (kanthi safety net timeout) iku tandha Node services sing ready kanggo production lan kasusu operasional sing pentinge nanging sering ora dilirokake.