nest-multi-transport

This module will allow you to pre-configure topics (initially tested for Kafka, but other transports should work)

@Controller()
export class KafkaController {
  /**
  * @param {string} stands for Global topics map key. handles <string|string[]> as value
  */
  @KafkaTopics('DYNAMIC_TOPICS_KEY') 
  async process(@Payload() data, @Ctx() context: KafkaContext) {
    console.log("Process message with dynamically defined topics.");
  }
}

#How it works

1. Specific "controller" decorator is created to add kafka topic candidate metadata.
2. Once await app.init() is called nestjs initialize all modules, providers and so on
3. OnModuleInit lifecycle hook runs and adds topics to map

@Injectable()
export class SomeService implements OnModuleInit {
  constructor(
    @Inject("KAFKA_TOPICS_MAP") private readonly kafkaTopicsMap: Map<string|symbol, string|string[]>
  ){ }

   async onModuleInit() {
    // You could fetch it from database or external API. Next lines are just for exampple
    this.kafkaTopicsMap.set("DYNAMIC_TOPICS_KEY", [
      'some_topic_1',
      'some_topic_2',
    ])
  }

4. Then KafkaDecoratorProcessorService processes all controller methods that decorated with specific decorator (ref 1st step) and decorates it with vanilla nestjs EventPattern.

Reflect.decorate(
  [EventPattern(topics)],
  type.prototype,
  prop,
  Reflect.getOwnPropertyDescriptor(type.prototype, prop),
);

Initial implementation roadmap

• define module (root or feature?)
• define topics map
• process topics on specific controllers