Hybrid application

A hybrid application listens for requests from two or more different sources. It can combine an HTTP server with a microservice listener, or combine several different microservice listeners. The createMicroservice() method doesn't support multiple servers, so in this case you create and start each microservice manually. To do this, connect INestMicroservice instances to the INestApplication instance with the connectMicroservice() method.

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

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

Hint The app.listen(port) method starts an HTTP server on the specified port. If your application doesn't handle HTTP requests, use the app.init() method instead.

Notice The order of these calls matters. With await app.startAllMicroservices() first (as above), the microservices begin consuming messages before the application's lifecycle hooks (such as onModuleInit and onApplicationBootstrap) have completed. Call app.listen() (or app.init()) before startAllMicroservices() if your handlers must not receive messages until every module has fully initialized.

To connect multiple microservice instances, call connectMicroservice() once for each microservice:

const app = await NestFactory.create(AppModule);
// microservice #1
const microserviceTcp = app.connectMicroservice<MicroserviceOptions>({
  transport: Transport.TCP,
  options: {
    port: 3002,
  },
});
// microservice #2
const microserviceRedis = app.connectMicroservice<MicroserviceOptions>({
  transport: Transport.REDIS,
  options: {
    host: 'localhost',
    port: 6379,
  },
});

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

In a hybrid application with multiple microservices, you can bind @MessagePattern() to a single transport strategy (for example, NATS) by passing a second argument that identifies the transport. For the built-in strategies, this is a value of the Transport enum; for a custom transporter, it is the transportId symbol of its server class.

@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(...);
}
@MessagePattern('topic.time.us', XYZServer.Transport) // XYZServer is a custom transporter
getXYZDate(@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(...);
}

@Bind(Payload())
@MessagePattern('topic.time.us', XYZServer.Transport)
getXYZDate(data) {
  return new Date().toLocaleTimeString(...);
}

Hint@Payload(), @Ctx(), Transport and NatsContext are imported from @nestjs/microservices. XYZServer.Transport here stands for the transportId symbol exposed by the custom transporter.

Sharing configuration#

By default, connected microservices don't inherit the global pipes, interceptors, guards, and filters configured for the main (HTTP-based) application. This applies both to enhancers registered with the useGlobal*() methods and to those registered as providers with the APP_PIPE, APP_INTERCEPTOR, APP_GUARD, and APP_FILTER tokens. To inherit this configuration, set the inheritAppConfig property in the options object passed as the second argument of connectMicroservice():

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

Hint A connected microservice registers its message handlers as soon as connectMicroservice() is called. When you use inheritAppConfig, call app.useGlobalPipes(), app.useGlobalGuards(), and the other useGlobal*() methods beforeconnectMicroservice(), otherwise the enhancers they register won't apply to the microservice's handlers.