Namespaced Config & Hooks — Series 3

Preview — 3 of 10 questions

With DB_POOL_SIZE unset, what does database.poolSize become?

javascript

ConfigModule.forRoot({
  validationSchema: Joi.object({ DB_POOL_SIZE: Joi.number().default(10) }),
  load: [registerAs('database', () => ({ poolSize: Number(process.env.DB_POOL_SIZE ?? 20) }))],
});

A10, because schema defaults take precedence over factory defaults

B20 — the factory reads process.env directly, and whether the schema's default has been written back to the environment is an implementation detail you should not depend on; keeping the default in exactly one place removes the ambiguity

CNaN, since neither default applies

DBoth are applied and the values are summed

What is the argument, and why is it useful?

javascript

@Injectable()
export class QueueService implements OnApplicationShutdown {
  onApplicationShutdown(signal?: string) {
    this.logger.log(`Shutting down after ${signal ?? 'programmatic close'}`);
  }
}

AThe exit code the process is about to return

BThe name of the module being destroyed

CThe number of milliseconds remaining in the grace period

DThe signal that triggered the shutdown — SIGTERM from an orchestrator, SIGINT from a local Ctrl-C — or undefined when app.close() was called directly; distinguishing them lets a deployment shutdown drain carefully while a local interrupt exits quickly

Which initialises first?

javascript

@Module({ imports: [CacheModule, SearchModule] })
export class AppModule {}
// both implement onModuleInit

ANeither order is guaranteed in a way you should depend on: Nest orders initialisation by the dependency graph, and two modules with no relationship between them have no defined relative order — if one genuinely needs the other ready, that dependency should be declared with an imports entry rather than inferred from position

BCacheModule, because it appears first in the array

CSearchModule, because initialisation walks the array in reverse

DBoth run concurrently, so either may finish first

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