Graceful shutdown trong Node.js là gì? Tại sao quan trọng?

Question

Luyện Phỏng Vấn IT · Accepted Answer

Graceful shutdown đảm bảo zero data loss và zero error responses khi deploy/restart.

Implementation pattern: process.on('SIGTERM', async () => { server.close(async () => { await db.disconnect(); await redis.quit(); process.exit(0); }); }) — server.close() stop accepting new connections nhưng chờ existing connections finish.
Connection draining: set timeout 30s cho in-flight requests — nếu quá timeout force close.
Health check: Kubernetes gửi SIGTERM sau khi remove pod khỏi load balancer (readiness probe fails) → khoảng trống 5-10s để LB drain traffic trước khi process nhận SIGTERM — config terminationGracePeriodSeconds: 30 trong K8s.
Kubernetes flow: SIGTERM → preStop hook (sleep 5s để LB drain) → app nhận SIGTERM → graceful shutdown → SIGKILL nếu quá terminationGracePeriodSeconds.
Track in-flight: let connections = 0; app.use((req, res, next) => { connections++; res.on('finish', () => connections--); next(); }) — chờ connections về 0 hoặc timeout.

Pitfall: không handle SIGINT (Ctrl+C local dev) — thêm cả process.on('SIGINT', handler).