NestJS - Communication between 2 microservice - nestjs

Question

I built a Http app and 2 microservices using TCP protocol.
This is my application diagram.
// Http App/app.service.ts
constructor() {
this.accountService = ClientProxyFactory.create({
transport: Transport.TCP,
options: {
host: 'localhost',
port: 8877,
},
});
this.friendService = ClientProxyFactory.create({
transport: Transport.TCP,
options: {
host: 'localhost',
port: 8080,
},
});
}
I tried to send message from Account Service to Friend Service by #Messagepattern().
ClientProxy is set up each service. But it doesn't work.
I read offical documentaion #nestjs/microservices, But i don't know which one is appropriate.
Is there right way to send message from one microservice to another microservice?

Answer 1

You need to set up a message broker, something like RabbitMQ or Kafka, ie for RabbitMQ enter the command below and create a RabbitMQ container.
docker run -it --rm --name rabbitmq -p 0.0.0.0:5672:5672 -p 0.0.0.0:15672:15672 -d rabbitmq:3-management
Then pass RabbitMQ options to your main.ts bootstrap function:
async function bootstrap() {
const rabbitmqPort = 5672
const rabbitmqHost = 127.0.0.1
const app = await NestFactory.create(AppModule);
app.connectMicroservice<MicroserviceOptions>({
transport: Transport.RMQ,
options: {
urls: [
`amqp://${rabbitmqHost}:${rabbitmqPort}`,
],
queue: 'myqueue',
queueOptions: {
durable: false,
},
},
});
app
.startAllMicroservices(() => {
logger.log('Microservice is listening!');
})
.listen(3000, () => {
logger.log('Api Server is listening on 3000');
});
}
bootstrap();
For receiving messages:
#MessagePattern('my_pattern')
async myController(
#Payload() data: MYDTO,
): Promise<MY TYPE> {
return await this.accountService.myFunction(data);
}
Now when a client sends a message on myqueue with my_pattern pattern, the data that client sends will be data which comes from #playload() annotation.
For sending messages on any queue you need to add RabbitMQ configurations to your application module, ie account.module.ts, by the assumption that you want to send a message on FriendService
const rabbitmqPort = 5672
const rabbitmqHost = 127.0.0.1
#Module({
imports: [
ClientsModule.registerAsync([
{
name: 'Friend',
useFactory: {
transport: Transport.RMQ,
options: {
urls: [
`amqp://${rabbitmqHost}:${rabbitmqPort}`,
],
queue: 'friend_queue',
queueOptions: {
durable: false,
},
},
}
},
]),
],
controllers: [AccountController],
providers: [AccountService],
})
export class AccountModule {}
And then inject Friend client to your service constructor like this:
#Inject('Friend')
private friendClient: ClientProxy,
Send messages like this:
const myVar = await this.friendClient.send('Some_pattern', {SOME DATA}).toPromise();
Set up all the above configurations for your both microservices and it shall work.