NodeJS Microservices with NestJS, Kafka, and Kubernetes - Part 1

api-request.sh

curl --location --request POST 'http://localhost:3000/services' \
--header 'Content-Type: application/json' \
--data-raw '{
    "name": "Web Development",
    "description": "description for Web Development"
}'

create-nestjs-api.sh

npm i -g @nestjs/cli
mkdir microservices-nestjs-k8
cd microservices-nestjs-k8
git init 
# make sure to create the repository on github under your account and add the remote origin
git remote add origin https://github.com/thiagotigaz/microservices-nestjs-k8.git
nest new -g api
cd api
npm i @nestjs/microservices kafkajs class-validator @nestjs/mapped-types
npm run start

create-service.dto.ts

import { IsNotEmpty, IsString, MaxLength } from 'class-validator';

export class CreateServiceDto {
  @MaxLength(64)
  @IsString()
  @IsNotEmpty()
  name: string;

  @MaxLength(255)
  @IsString()
  @IsNotEmpty()
  description: string;

  tags: string[];
}

services.module.ts

import { Module } from '@nestjs/common';
import { ServicesService } from './services.service';
import { ServicesController } from './services.controller';
import { ClientKafka, ClientsModule, Transport } from '@nestjs/microservices';

@Module({
  imports: [
    ClientsModule.register([
      {
        name: 'CLIENT_KAFKA',
        transport: Transport.KAFKA,
        options: {
          client: {
            clientId: 'services',
            brokers: ['host.docker.internal:9094'],
          },
          consumer: {
            groupId: 'services',
          },
        },
      },
    ]),
  ],
  controllers: [ServicesController],
  providers: [
    ServicesService,
    {
      provide: 'KAFKA_PRODUCER',
      useFactory: async (kafkaClient: ClientKafka) => {
        return kafkaClient.connect();
      },
      inject: ['CLIENT_KAFKA'],
    },
  ],
})
export class ServicesModule {}

services.service.ts

import { Inject, Injectable } from '@nestjs/common';
import { CreateServiceDto } from './dto/create-service.dto';
import { UpdateServiceDto } from './dto/update-service.dto';
import { Producer } from '@nestjs/microservices/external/kafka.interface';

@Injectable()
export class ServicesService {
  constructor(@Inject('KAFKA_PRODUCER') private kafkaProducer: Producer) {}

  create(createServiceDto: CreateServiceDto) {
    const id = Math.floor(Math.random() * 100);
    this.sendKafkaEvent(`${id}`, {
      eventType: 'ServiceCreated',
      id,
      ...createServiceDto,
    });
    return 'This action adds a new service';
  }

  findAll() {
    return `This action returns all services`;
  }

  findOne(id: number) {
    return `This action returns a #${id} service`;
  }

  update(id: number, updateServiceDto: UpdateServiceDto) {
    updateServiceDto.id = id;
    this.sendKafkaEvent(`${id}`, {
      eventType: 'ServiceUpdated',
      ...updateServiceDto,
    });
    return `This action updates a #${id} service`;
  }

  remove(id: number) {
    this.sendKafkaEvent(`${id}`, { eventType: 'ServiceDeleted', id });
    return `This action removes a #${id} service`;
  }

  sendKafkaEvent(key, value) {
    this.kafkaProducer.send({
      topic: 'services',
      messages: [{ key, value: JSON.stringify(value) }],
    });
  }
}

update-service.dto.ts

import { PartialType } from '@nestjs/mapped-types';
import { CreateServiceDto } from './create-service.dto';
import { IsNotEmpty } from 'class-validator';

export class UpdateServiceDto extends PartialType(CreateServiceDto) {
  @IsNotEmpty()
  id: number;
}