Cross-Cutting Concerns — Series 2

Preview — 3 of 10 questions

What does bufferLogs: true accomplish?

javascript

const app = await NestFactory.create(AppModule, { bufferLogs: true });
app.useLogger(app.get(PinoLogger));
await app.listen(3000);

AIt batches log writes to reduce syscalls under load

BIt holds back everything Nest logs during bootstrap and replays it through the custom logger once useLogger() is called — otherwise those early lines would have already gone out through the default console logger, unstructured

CIt suppresses bootstrap logging entirely

DIt stores logs in memory so a later request can retrieve them

What does app.close() guarantee, and what does it not?

javascript

process.on('SIGTERM', async () => {
  await app.close();
});

AIt waits indefinitely for every open connection, including idle keep-alive ones, to close on its own

BIt aborts in-flight requests immediately so shutdown is instant

CIt has no effect unless enableShutdownHooks() was called

DIt stops accepting new connections and runs the shutdown hooks, but long-running handlers and idle keep-alive sockets can keep the process alive past the orchestrator's grace period — so a real drain also needs a readiness probe flipped to failing first, and bounded handler durations

Why should the liveness probe not check the database?

javascript

@Get('health/live')  live()  { return this.health.check([]); }
@Get('health/ready') ready() {
  return this.health.check([() => this.db.pingCheck('database')]);
}

ABecause liveness answers "should this process be restarted?" — and a database outage is not something a restart fixes, so making liveness depend on it turns a dependency blip into a restart storm across every instance

BBecause liveness probes are called too frequently for any I/O to be acceptable

CBecause Terminus forbids indicators on liveness endpoints

DBecause readiness and liveness must check disjoint sets of dependencies by specification

Answer all 10 questions (7 more), see explanations for every answer, and track your score.