Nest.js Microservices

How

Why

What

Nest.js Microservices

Motivation & advantages

Code reuse - Each service can serve many apps

Why

Scalable R&D - Each service can be managed by a separate team
Separate repositories, testing & deployment schedule

Resources - Easier for DevOps to manage the load separately
Scale each process individually
Some services are more popular than others

Challenges & tradeoffs

Testing - integration testing are more complex

Why

Memory allocation -

Monoliths are easier - using DI - same process - the same memory

Microservices run on separate processes - separate memory

They need a standard way to communicate with each other

Monoliths - DI

Injecting a reference to an instantiated object stored in the same memory process, then invoking methods on it...

import { PetsService } from './pets.service';

@Controller('pets')
export class PetsController {
  
  constructor(private readonly petsService: PetsService) {}

  @Get()
  getAllPets() {
    return this.petsService.getAllPets();
  }

}

How

Microservices - DI

Injecting a microservice client proxy, who knows how to communicate with it and get results.

import { Inject, Injectable } from '@nestjs/common';
import { ClientProxy } from '@nestjs/microservices';

@Injectable()
export class AppService {
  constructor(@Inject('SOME_SERVICE') private client: ClientProxy) {}

  async getHello() {
    return await this.client.send<string>('hello', {});
  }

}

How

Supported

Transports

How

Basic TCP

direct

Redis

MQTT

NATS

RabbitMQ

Kafka

Message
Brokers

gRPC

Remote
Procedure call

How

Tight coupling -

The client app needs to know about the microservice existence
and how to contact it. This info will be stored in config files...
When you have dozens or hundreds of microservices, it becomes a problem
as things move and change all the time...

How

Loose coupling -

A message broker like Redis helps us decouple the different microservices from our apps. Managing many microservices becomes a lot easier when we route all of our communication through a single address. That goes for monitoring as well...

Demo time!

How