Kepiye NestJS nyukupi microservices?

Question

IT Interview Practice · Accepted Answer

NestJS duwe **dukungan microservices sing built-in** — bisa tumaksi minangka microservice sing komunikasi liwat macem-macem **transports** (TCP, Redis, NATS, RabbitMQ, Kafka, gRPC) kejaba HTTP, nganggo model programming sing konsisten lan berbasis pesan. Struktur NestJS sing padha (modules, services, DI) tetap berlaku; mung transport lan message patterns sing ganti.

## Nggawe microservice

```ts
// a microservice listens on a transport instead of HTTP
const app = await NestFactory.createMicroservice(AppModule, {
  transport: Transport.TCP,             // or REDIS, NATS, RMQ, KAFKA, GRPC
  options: { host: "0.0.0.0", port: 3001 },
});
await app.listen();
```

## Message patterns vs event patterns

```ts
@Controller()
export class MathController {
  // REQUEST-RESPONSE: respond to a message and RETURN a result (RPC-style)
  @MessagePattern({ cmd: "sum" })
  sum(data: number[]): number {
    return data.reduce((a, b) => a + b, 0);   // the caller awaits this result
  }

// EVENT-BASED: react to an event, NO response expected (fire-and-forget)
  @EventPattern("order_created")
  handleOrderCreated(data: OrderDto) {
    this.processOrder(data);                   // just react; nothing returned
  }
}
```

Rong gaya komunikasi: **`@MessagePattern`** kanggo request-response (sing njaluk nantung hasil, kaya RPC) lan **`@EventPattern`** kanggo events (fire-and-forget, decoupled — publisher ora nantung).

## Njaluk microservice liyane (client)

```ts
@Injectable()
export class AppService {
  constructor(@Inject("MATH_SERVICE") private client: ClientProxy) {}

async getSum() {
    // send() → request-response (returns an Observable of the result)
    return this.client.send({ cmd: "sum" }, [1, 2, 3]);
    // emit() → fire an event (no response)
    this.client.emit("order_created", orderData);
  }
}
```

`ClientProxy` (dikonfigurasi liwat `ClientsModule`) ngirim messages/events menyang services liyane — `send()` kanggo request-response, `emit()` kanggo events.

## Hybrid applications

```ts
// an app can serve HTTP AND connect microservice transports simultaneously
const app = await NestFactory.create(AppModule);
app.connectMicroservice({ transport: Transport.RMQ, options: {...} });
await app.startAllMicroservices();
await app.listen(3000);   // HTTP too
```

## Pilihan transport penting

```text
TCP   → simple direct service-to-service
Redis/NATS → lightweight pub/sub messaging
RabbitMQ/Kafka → robust message queues/streams (durability, retries, decoupling)
gRPC  → high-performance, strongly-typed RPC (protobuf)
→ Async message brokers (RMQ/Kafka) give decoupling & resilience; gRPC gives speed+typing.
```

## Apa gunane

Dukungan microservices NestJS sing built-in penting amarga ngidini sampeyan nggawe sistem terdistribusi nganggo struktur NestJS sing *padha* familiar (modules, providers, DI, decorators) sanajan ngganti HTTP karo transports berbasis pesan — kauntungan produktivitas lan konsistensi sing gedhé.

Mahami iki penting kanggo merancang sistem scalable: pembedahan **message-pattern (request-response) vs event-pattern (fire-and-forget)** langsung nyawiji karo pilihan komunikasi microservices sing fundamental — RPC-style calls sing sinkron versus events asinkron lan decoupled (sing terakhir, liwat message brokers, nyediyakake resilience lan loose coupling sing agawe microservices kuat).
"); Ngertos carane nggawe microservices, nemtokake message/event handlers, njaluk services liyane liwat `ClientProxy`, nggawe hybrid HTTP+microservice apps, lan milih transports (pub/sub sing ringan versus durable queues kaya Kafka/RabbitMQ versus gRPC sing high-performance) penting kanggo senior-level knowledge kanggo design distributed back-ends.

Kandhane microservices nambah kompleksitas (lan ora mesthi bener nanding monolith), NestJS agawe implementasi bersih lan konsisten, nggawe topik arsitektur iki penting kanggo nggawe sistem NestJS terdistribusi lan scale gedhé.

Nggawe microservice

Message patterns vs event patterns

Njaluk microservice liyane (client)

Hybrid applications

Pilihan transport penting

Apa gunane

Pitakon sing gegandhengan