Graceful Shutdown for Node: Drain Correctly on Kubernetes and ECS

// src/shutdown.ts
import type { Server } from "node:http";

type Closer = () => Promise<void>;
const closers: Closer[] = [];
let shuttingDown = false;

export function onShutdown(fn: Closer) { closers.push(fn); }
export function isShuttingDown() { return shuttingDown; }

export function installShutdown(server: Server, budgetMs = 25_000) {
 const run = async (signal: string) => {
 if (shuttingDown) return;
 shuttingDown = true;
 console.log(JSON.stringify({ msg: "shutdown_start", signal }));
 readiness.set(false); // ✅ ALB/K8s stop new traffic
 const timer = setTimeout(() => {
 console.error(JSON.stringify({ msg: "shutdown_timeout" }));
 process.exit(1);
 }, budgetMs);
 try {
 await new Promise<void>((res) => server.close(() => res()));
 for (const c of closers) await c();
 clearTimeout(timer);
 process.exit(0);
 } catch (err) {
 console.error(err);
 process.exit(1);
 }
 };
 process.on("SIGTERM", () => void run("SIGTERM"));
 process.on("SIGINT", () => void run("SIGINT"));
}

// ❌ Ignoring SIGTERM — K8s waits, then SIGKILL mid-request
// no handler at all

// src/sqs-consumer.ts
import { onShutdown } from "./shutdown.js";

let running = true;
onShutdown(async () => {
 running = false; // ✅ stop long-polling
 await inFlight.drain(); // wait for handlers with AbortSignal
});

export async function loop(poll: () => Promise<Message[]>) {
 while (running) {
 const batch = await poll();
 await Promise.all(batch.map((m) => handle(m, AbortSignal.timeout(10_000))));
 }
}

# deployment.yaml excerpt
lifecycle:
 preStop:
 exec:
 command: ["sh", "-c", "sleep 10"]
terminationGracePeriodSeconds: 45