Hybrid application

A hybrid application is one that listens for requests from two or more different sources. This can combine an HTTP server with a microservice listener or even just multiple different microservice listeners. The default createMicroservice method does not allow for multiple servers so in this case each microservice must be created and started manually. In order to do this, the INestApplication instance can be connected with INestMicroservice instances through the connectMicroservice() method.

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

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

info Hint the app.listen(port) method starts an HTTP server on the specified address. If your application does not handle HTTP requests then you should use the app.init() method instead.

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: {
    host: 'localhost',
    port: 6379,
  },
});

await app.startAllMicroservices();
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.

@@filename()
@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(...);
}
@@switch
@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(...);
}

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

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<MicroserviceOptions>(
  {
    transport: Transport.TCP,
  },
  { inheritAppConfig: true },
);

Sharing configuration​

Sharing configuration