Why do I need to define queue name while creating microservice?

Question

I want to have a hybrid NestJS app, HTTP + RabbitMQ. But don't get if I should create different microservices for each queue.

I have followed NestJS' RabbitMQ guide (https://docs.nestjs.com/microservices/rabbitmq) and GitHub example (https://github.com/nestjs/nest/tree/master/sample/03-microservices).

main.ts

app.connectMicroservice({
    transport: Transport.RMQ,
    options: {
      urls: [`amqp://user:user@hostname:5672`],
      queue: "cats_queue",
      queueOptions: { durable: false },
      prefetchCount: 1,
    }
  });
...
await app.startAllMicroservicesAsync();

app.module.ts (module import)

ClientsModule.register([{
      name: "CATS_QUEUE", transport: Transport.RMQ, options: {
        urls: [`amqp://user:user@hostname:5672`],
        queue: "cats_queue",
        queueOptions: { durable: false },
        prefetchCount: 1
      }
    }])

app.controller.ts

constructor(
    @Inject("CATS_QUEUE") private readonly client: ClientProxy
  ) {
  }
  @Get("mq")
  mq(): Observable<number> {
    const pattern = { cmd: "sum" };
    const data = [1, 2, 3, 4, 5];
    return this.client.send<number>(pattern, data);
  }

  @MessagePattern({ cmd: "sum" })
  sum(data: number[]): number {
    console.log("MESSAGE RECEIVED : " + data.toString());
    return (data || []).reduce((a, b) => a + b);
  }

As I understood, I need to define ClientsModule.register() for each queue in app.module.ts. But why I also need to define RabbitMQ queue name while creating microservice? Do I need to create different microservices for each queue?

Answer 1

I'm not a NestJS user, but it seems logical that when you use queues to send messages between your microservices, you will need a queue for each microservice (not the other way around).

Queues are used to send (TO) and receive(Process) messages between independent components asynchronously.

Does that make sense?