Description

NATS v2 strategy and client module for Nest

Installation

$ npm i --save @nestjs-ex/nats-strategy

Usage

To use the Nats transporter, pass the following options object to the createMicroservice() method:

import { NestFactory } from '@nestjs/core';
import { NatsStrategy } from '@nestjs-ex/nats-strategy';
import { AppModule } from './app.module';

async function bootstrap() {
  const app = await NestFactory.createMicroservice(
    AppModule,
    {
      strategy: new NatsStrategy({
        servers: '127.0.0.1:4222',
        user: 'jenny',
        pass: '867-5309',
      })
    },
  );
  app.listen(() => console.log('Microservice is listening'));
}
bootstrap();

Client

To create a client instance with the NatsClientModule, import it and use the register() method to pass an options object with the same properties shown above in the createMicroservice() method.

@Module({
  imports: [
    NatsClientModule.register({
      servers: '127.0.0.1:4222',
      user: 'jenny',
      pass: '867-5309',
      name: 'example-client'
    }),
  ]
  ...
})

Once the module has been imported, we can inject an instance of the NatsClient shown above

constructor(
  private client: NatsClient
) {}

Quite often you might want to asynchronously pass your module options instead of passing them beforehand. In such case, use registerAsync() method, that provides a couple of various ways to deal with async data.

1. Use factory

NatsClientModule.registerAsync({
  useFactory: () => ({
    servers: '127.0.0.1:4222',
    user: 'jenny',
    pass: '867-5309',
    name: 'example-client'
  })
});

Obviously, our factory behaves like every other one (might be async and is able to inject dependencies through inject).

NatsClientModule.registerAsync({
  imports: [ConfigModule],
  useFactory: async (configService: ConfigService) => ({
    servers: configService.getString('NATS_SERVERS'),
    name: configService.getString('NATS_NAME')
  }),
  inject: [ConfigService],
}),

2. Use class

NatsClientModule.registerAsync({
  useClass: NatsClientConfigService
});

Above construction will instantiate NatsClientConfigService inside NatsClientModule and will leverage it to create options object.

class NatsClientConfigService implements NatsClientOptionsFactory {
  createNatsClientOptions(): NatsClientModuleOptions {
    return {
      servers: '127.0.0.1:4222',
      user: 'jenny',
      pass: '867-5309',
      name: 'example-client'
    };
  }
}

3. Use existing

NatsClientModule.registerAsync({
  imports: [ConfigModule],
  useExisting: ConfigService,
}),

It works the same as useClass with one critical difference - NatsClientModule will lookup imported modules to reuse already created ConfigService, instead of instantiating it on its own.

Stay in touch

• Author - Thanh Pham

License

Nest is MIT licensed.