Pub/Sub Wrapper for NestJS

Description

This is a custom transport strategy wrapper for Google Cloud Pub/Sub within the NestJS framework. In other words, it provides a simple way to publish and subscribe to a topic.

Installation

This service is built with Node (v16.14.2 using npm@8.5.0) and NestJS.

npm install @softrizon/pubsub

Usage

Publish messages

• Module configuration

import { Module } from '@nestjs/common';
import { PubSubModule } from '@softrizon/pubsub';
import { MessageService } from './message.service';

@Module({
  imports: [
    PubSubModule.forRoot({
      defaultTopicName: 'my-topic',
      defaultFormat: 'my-format',
      config: { projectId: 'my-project' },
    }),
  ],
  providers: [MessageService],
})
export class AppModule {}

• Inject the service (e.g., MessageService) to emit messages.

import { Injectable } from '@nestjs/common';
import { PubSubService } from '@softrizon/pubsub';

@Injectable()
export class MessageService {
  constructor(private pubsub: PubSubService) {}

  emit<T = any>(pattern: string, data: T): void {
    const emitOptions = {
      event: pattern;
      data: data;
      topic: 'another-topic'; // optional, default: defaultTopicName
      format: 'another-format'; // optional, default: defaultFormat
    }
    this.pubsub.emit(emitOptions);
  }
}

Subscribe on messages

• Server configuration

import { NestFactory } from '@nestjs/core';
import { MicroserviceOptions } from '@nestjs/microservices';
import { PubSubServer } from '@softrizon/pubsub';
import { AppModule } from './app.module';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);

  app.connectMicroservice<MicroserviceOptions>({
    strategy: new PubSubServer({
      config: { projectId: 'my-project' },
      topic: 'my-topic',
      subscriptions: ['my-subscription'],
    }),
  });

  app.startAllMicroservices();
  await app.listen(3000);
}
bootstrap();

• Subscribe to message pattern

import { Controller } from '@nestjs/common';
import { MessagePattern, Payload } from '@nestjs/microservices';

@Controller()
export class MessagesEventController {
  @MessagePattern({ event: 'MY_PATTERN', format: 'JSON_API_V1' })
  async doSomething(@Payload() data: any): Promise<void> {
    // do something with data...
  }
}

Note: Do not forget to register the controller in the corresponding module. In the example above, the message pattern is an object with the keys event and format. This is a practice useful for filtering events in the one-to-many pubsub architecture. If you don't need this kind of filtering, you may need to extend PubSubServer and override the handleMessage and getData methods.

Read more

Visit the main page to learn more about its key features, configurations, limitations, and API.

Author

Developed by Softrizon.

License

This project is MIT-licensed.