NodeJS Microservices with NestJS, Kafka, and Kubernetes - Part 2

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-microservices-app.sh

# make sure you are on the root of the repository
nest new -g microservices
cd microservices
npm i @nestjs/microservices kafkajs @nestjs/mapped-types class-transformer class-validator @nestjs/event-emitter

create-service.dto.ts

import { IsNotEmpty, IsString, MaxLength } from 'class-validator';
import { EventDto } from './event.dto';
import { PartialType } from '@nestjs/mapped-types';

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

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

  tags: string[];
}

delete-service.dto.ts

import { PartialType } from '@nestjs/mapped-types';
import { IsNotEmpty } from 'class-validator';
import { EventDto } from './event.dto';

export class DeleteServiceDto extends PartialType(EventDto) {
  @IsNotEmpty()
  id: number;
}

event.dto.ts

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

export class EventDto {
  @IsString()
  @IsNotEmpty()
  eventType: string;
}

kafka-service.dto.ts

import { Type } from 'class-transformer';
import { IsNotEmpty, ValidateNested } from 'class-validator';
import { CreateServiceDto } from './create-service.dto';
import { UpdateServiceDto } from './update-service.dto';
import { DeleteServiceDto } from './delete-service.dto';
import { EventDto } from './event.dto';

export class KafkaServiceDto {
  @Type(() => EventDto, {
    discriminator: {
      property: 'eventType',
      subTypes: [
        { value: CreateServiceDto, name: 'ServiceCreated' },
        { value: UpdateServiceDto, name: 'ServiceUpdated' },
        { value: DeleteServiceDto, name: 'ServiceDeleted' },
      ],
    },
    keepDiscriminatorProperty: true,
  })
  @ValidateNested()
  @IsNotEmpty()
  value: CreateServiceDto | UpdateServiceDto | DeleteServiceDto;
}

nestjs-generate-controller-services.sh

 nest g co services

services.controller.ts

import { Controller, Logger, ValidationPipe } from '@nestjs/common';
import { EventPattern, Payload } from '@nestjs/microservices';
import { KafkaServiceDto } from './dto/kafka-service.dto';

import { CreateServiceDto } from './dto/create-service.dto';
import { UpdateServiceDto } from './dto/update-service.dto';
import { EventEmitter2, OnEvent } from '@nestjs/event-emitter';
import { DeleteServiceDto } from './dto/delete-service.dto';

@Controller()
export class ServicesController {
  constructor(private eventEmitter: EventEmitter2) {}

  @EventPattern('services')
  serviceEvent(@Payload(new ValidationPipe()) { value }: KafkaServiceDto) {
    Logger.debug(value, 'ServicesController - serviceEvent');
    this.eventEmitter.emit(value.eventType, value);
  }

  @OnEvent('ServiceCreated')
  handleServiceCreatedEvent(createServiceDto: CreateServiceDto) {
    Logger.debug(
      createServiceDto,
      'ServicesController - handleServiceCreatedEvent',
    );
  }

  @OnEvent('ServiceUpdated')
  handleServiceUpdatedEvent(updateServiceDto: UpdateServiceDto) {
    Logger.debug(
      updateServiceDto,
      'ServicesController - handleServiceUpdatedEvent',
    );
  }

  @OnEvent('ServiceDeleted')
  handleServiceDeletedEvent(deleteServiceDto: DeleteServiceDto) {
    Logger.debug(
      deleteServiceDto,
      'ServicesController - handleServiceDeletedEvent',
    );
  }
}

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;
}