@melkonline/nestjs-microservices-cqrs

A progressive Node.js framework for building efficient and scalable server-side applications.

nestjs-microservices-cqrs

Description

NestJS Microservices CQRS

NestJS Microservices CQRS - Modified CQRS module to subscribe/publish Events globally instead of locally

How It Works?

Overriding @nestjs/cqrs module, its EventBus is changed in order to subscribe to events globally when registering Handlers.

Publishing Events will emit them instead of executing their corresponding handlers.

By default, any Event to which at least one Handler is registered, will be subscribed Globally.

Also, publish method of this module's EventBus will publish the Event globally, and not locally.

Therefore, the Handler will be executed after we received the Event from the network.

Installation

$ npm install --save @melkonline/nestjs-microservices-cqrs

Quick Start

In your main.ts:

import { NestjsMicroservicesCqrs } from "@melkonline/nestjs-microservices-cqrs";

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  app.connectMicroservice(app.get(NestjsMicroservicesCqrs).init(microserviceConfig), {
    inheritAppConfig: true,
  });
  await app.startAllMicroservices();
  app.get(NestjsMicroservicesCqrs).run();
  app.listen(3456);
}
bootstrap();

In your app.module.ts:

import { NestjsMicroservicesCqrsModule } from '@melkonline/nestjs-microservices-cqrs';

@Module({
  imports: [
      /** All other modules */
      NestjsMicroservicesCqrsModule
  ],
  controllers: [/* ...Controllers */],
  providers: [
      /**
        ...Services
        ...CommandHandlers
        ...EventHandlers
       */
  ],
})
export class AppModule {}

In your Event:

import { SerializableEvent, ISerializableEvent } from '@melkonline/nestjs-microservices-cqrs';

export class TaskCreatedEvent extends SerializableEvent implements ISerializableEvent {
  constructor(public readonly createTaskDto: CreateTaskDto) {
    super();
  }
}

Using EventBus:

import { EventBus } from '@melkonline/nestjs-microservices-cqrs';
@Controller()
export class AppController {
  constructor(
    private readonly appService: AppService,
    private readonly eventBus: EventBus,
  ) {}

  @Get('test')
  test() {
    const data = new CreateTaskDto();
    data.type = 'testing the module';
    return this.eventBus.publish(new TaskCreatedEvent(data));
  }
}

Still Want local Events?

Simply add @LocalEvent() decorator to your Event class.

import { LocalEvent } from '@melkonline/nestjs-microservices-cqrs';

@LocalEvent()
export class TaskCreatedEvent implements IEvent {
  constructor(public readonly data: CreateTaskDto) {}
}

Such events will be neither subscribed, nor published globally, instead they will work locally as traditional.

Microservice Route Is Also Available:

Beside subscribing to the Event via Handler, you still can subscribe as a route via @EventPattern() decorator as traditional:

@Controller()
export class AppController {
  constructor(
    private readonly appService: AppService,
    private readonly eventBus: EventBus,
  ) {}

  @EventPattern('TaskCreatedEvent')
  someOtherWayToHandleOurEvent(@Payload() message) {
    console.log('someOtherWayToHandleOurEvent', message);
  }
}

License

NestJS Microservices CQRS is MIT licensed.