Cách xử lý unhandled Promise rejections trong Node.js?

Node.js 14 trở về trước: unhandled rejection chỉ print warning, process tiếp tục — silent failure nguy hiểm.

Node.js 15+: mặc định crash process với exit code 1 — breaking change.

Hierarchy xử lý đúng:

1. try/catch trong async functions là chính,
2. .catch() chain cho fire-and-forget promises,
3. process.on('unhandledRejection', (reason) => { logger.error('Unhandled rejection', reason); gracefulShutdown(1); }) là safety net cuối — không phải cơ chế chính. process.on('uncaughtException', (err) => { logger.error(err); gracefulShutdown(1); }) cho sync throws

Monitoring: gửi đến Sentry trước khi shutdown — Sentry.captureException(reason); await Sentry.flush(2000).

Graceful shutdown: stop accepting requests, wait for in-flight, close DB, exit.

Dùng ESLint rule @typescript-eslint/no-floating-promises để catch missing awaits lúc compile time — tốt hơn runtime detection.

Node.js 14 and earlier: unhandled rejections only print a warning and the process continues — silent failures are dangerous.

Node.js 15+: crashes the process with exit code 1 by default — a breaking change.

Proper handling hierarchy:

1. try/catch inside async functions is the primary mechanism,
2. .catch() chaining for fire-and-forget promises,
3. process.on('unhandledRejection', (reason) => { logger.error('Unhandled rejection', reason); gracefulShutdown(1); }) as a final safety net — not the primary mechanism. process.on('uncaughtException', (err) => { logger.error(err); gracefulShutdown(1); }) for synchronous throws

Monitoring: send to Sentry before shutting down — Sentry.captureException(reason); await Sentry.flush(2000).

Graceful shutdown: stop accepting requests, wait for in-flight requests, close DB connections, exit.

Use the ESLint rule @typescript-eslint/no-floating-promises to catch missing awaits at compile time — better than runtime detection.