Hybrid application

A hybrid application is one that both listens for HTTP requests, as well as makes use of connected microservices. The INestApplication instance can be connected with INestMicroservice instances through the connectMicroservice() method.

const app = await NestFactory.create(AppModule);
const microservice = app.connectMicroservice({
  transport: Transport.TCP,
});

await app.startAllMicroservicesAsync();
await app.listen(3001);

To connect multiple microservice instances, issue the call to connectMicroservice() for each microservice:

const app = await NestFactory.create(AppModule);
// microservice #1
const microserviceTcp = app.connectMicroservice<MicroserviceOptions>({
  transport: Transport.TCP,
  options: {
    port: 3001,
  },
});
// microservice #2
const microserviceRedis = app.connectMicroservice<MicroserviceOptions>({
  transport: Transport.REDIS,
  options: {
    url: 'redis://localhost:6379',
  },
});

await app.startAllMicroservicesAsync();
await app.listen(3001);

To bind @MessagePattern() to only one transport strategy (for example, MQTT) in a hybrid application with multiple microservices, we can pass the second argument of type Transport which is an enum with all the built-in transport strategies defined.

@MessagePattern('time.us.*', Transport.NATS)
getDate(@Payload() data: number[], @Ctx() context: NatsContext) {
  console.log(`Subject: ${context.getSubject()}`); // e.g. "time.us.east"
  return new Date().toLocaleTimeString(...);
}
@MessagePattern({ cmd: 'time.us' }, Transport.TCP)
getTCPDate(@Payload() data: number[]) {
  return new Date().toLocaleTimeString(...);
}

@Bind(Payload(), Ctx())
@MessagePattern('time.us.*', Transport.NATS)
getDate(data, context) {
  console.log(`Subject: ${context.getSubject()}`); // e.g. "time.us.east"
  return new Date().toLocaleTimeString(...);
}
@Bind(Payload(), Ctx())
@MessagePattern({ cmd: 'time.us' }, Transport.TCP)
getTCPDate(data, context) {
  return new Date().toLocaleTimeString(...);
}

Hint@Payload(), @Ctx(), Transport and NatsContext are imported from @nestjs/microservices.

Sharing configuration#

By default a hybrid application will not inherit global pipes, interceptors, guards and filters configured for the main (HTTP-based) application. To inherit these configuration properties from the main application, set the inheritAppConfig property in the second argument (an optional options object) of the connectMicroservice() call, as follow:

const microservice = app.connectMicroservice({
  transport: Transport.TCP
}, { inheritAppConfig: true });