Service Discovery POC

This POC is part of article published: https://www.linkedin.com/pulse/client-side-load-balance-spring-boot-microservice-docker-rodrigues/?published=t

These projects illustrate the service discovery & client load balance with microservices inter dependent.

• Components
  • eureka-service: Netflix OSS Service discovery
  • region-service: microservice exposing region services. This microservice depends on country-service
  • country-service: microservice exposing country services
• Features
  • Spring Boot: Spring Boot application
  • Eureka: service discovery
  • Ribbon: client side load balance
  • Feign: declarative rest client
  • Hystrix: circuit breaker implementation
  • H2: In Memory database
  • Spring Data JPA: declarative JPA implementation

Eureka Server

Default Eureka Server which runs on port 8761

Region Service

This microservice run on port 8080 and expose the following service:

  /region                     GET find all regions
  /region/{id}                GET find region by id
  /region/{id}/countries      GET find region and its countries, by region id

Below is the ribbon/feign client acting as country-service proxy

@RibbonClient("country-service")
@FeignClient("country-service")
public interface CountryServiceProxy {

    @GetMapping("country/region/{id}")
    List<CountryDTO> findByRegionId(@PathVariable("id") Integer id);
}

And here, the hystrix fallback defined for findByRegionId (countries by region id). When the service is down, the fallback method will return an empty country list

@Service
public class CountryService {
    
  // omitted
  
  @HystrixCommand(fallbackMethod= "findByRegionIdFallback")
  public List<CountryDTO> findByRegionId(Integer id) {
    return countryServiceProxy.findByRegionId(id);
  }

  public List<CountryDTO>  findByRegionIdFallback(Integer id, Throwable throwable){
    log.error("calling fallback..", throwable);
    return List.of(new CountryDTO());
  }
}

Country Service

This microservice run on ports 8081-8082 and expose the following services:

  /country                    GET find all countries
  /country/{id}               GET find country by id
  /country/region/{id}        GET find countries by region id (region-service dependent)

Build & Run with Docker

  $ cd service-discovery
  $ mvn clean pakage
  $ docker-compose up -d --build --scale country-service=2
  $ docker-compose ps

Test

• Check client registration on Eureka Server: http://localhost:8761
• Access http://localhost:8080/region/1/countries
• Check logs from country-service instance #1 and #2 and see the request being balanced

  $ docker ps -a --filter="name=country"
  $ docker logs <container id>

• Scale down country service to run one instance only

  $ docker-compose up -d --build --scale country-service=1
  $ docker-compose ps

• Access http://localhost:8080/region/1/countries

Environment

  $ uname -mprs
  Darwin 20.6.0 arm64 arm
  
  $ docker -v
  Docker version 20.10.11, build dea9396
  
  $ docker-compose -v
  docker-compose version 1.29.2, build 5becea4c
  
  $ java -version
  java version "11.0.13" 2021-10-19 LTS
  Java(TM) SE Runtime Environment 18.9 (build 11.0.13+10-LTS-370)
  Java HotSpot(TM) 64-Bit Server VM 18.9 (build 11.0.13+10-LTS-370, mixed mode)