Microservices Registration and Discovery using Spring Cloud and Eureka

January 17, 2021

Microservices Registration and Discovery using Spring Cloud, Eureka

This blog post walks through an implementation pattern and a working setup with multiple microservices where they get registered with Eureka and the client can discover them and invoke them.

What is Eureka

Eureka is a REST-based service that provides support for discovering other services so that clients can use the Eureka service to discover and call them.

Why we need Discovery Service

In a microservices architecture, each service typically runs on a different URL or IP address. Clients need a way to know when new microservices are added or existing ones go down for maintenance. Discovery service provides that mechanism—services register themselves, and clients query the discovery service to know available microservices.

Project Achievement

In this project, we will build:

  • A Eureka Discovery Service
  • An Article Microservice (CRUD operations)
  • A Client Microservice (consumes the Article service)

Goal: invoke a target service without hardcoding URLs, IPs, or ports, by resolving via service discovery.

Technology Used

  • Java 11
  • Apache Maven 3.5.0
  • Spring Boot 2.2.6
  • Spring Cloud Hoxton.SR1
  • Netflix Ribbon 2.3.0
  • Open Feign
  • JSON

Discovery Server

Add the Eureka Discovery Server dependency:



  org.springframework.cloud
  spring-cloud-starter-netflix-eureka-server

application.properties:


server.port=8761
eureka.client.serviceUrl.defaultZone=http://127.0.0.1:8761/eureka/
eureka.client.healthcheck.enabled=true

Main Application:


@EnableEurekaServer
@SpringBootApplication
public class ServiceDiscovery {
  public static void main(String[] args) {
    SpringApplication.run(ServiceDiscovery.class, args);
  }
}

Article Service

Add Eureka Client dependency:



  org.springframework.cloud
  spring-cloud-starter-netflix-eureka-client

application.properties:


server.port=9051
eureka.client.serviceUrl.defaultZone=http://127.0.0.1:8761/eureka/
eureka.client.register-with-eureka=true
spring.application.name=article-service

Main Application:


@SpringBootApplication
@EnableEurekaClient
@EnableDiscoveryClient
public class ArticleMicroservice {
  public static void main(String args[]) {
    SpringApplication.run(ArticleMicroservice.class, args);
  }
}

REST Endpoints:

  • GET /api/articles
  • GET /api/articles/{id}
  • POST /api/articles
  • DELETE /api/articles/{id}

Sample Response


[
  {
    "id": "America-Travel",
    "name": "America Travel",
    "description": "Places to travel in America ...",
    "category": "Travel"
  }
]

Article Client Service

This is another Spring Boot service that discovers and calls the Article service using Ribbon/Feign.

Consumer Controller Example:


@RestController
public class RibbonController {
  @Autowired
  private RestTemplate restTemplate;

  @RequestMapping(value = "render", method = RequestMethod.GET,
                  produces = MediaType.APPLICATION_JSON_VALUE)
  public ResponseEntity<String> renderArticles() throws Exception {
    JsonNode repos =
      restTemplate.getForObject("http://article-service-consumer/api/articles", JsonNode.class);
    ...
  }
}

Start Microservices

  1. Clone repo: git clone https://github.com/siddharthagit/spring-boot-sdc
  2. Run each service: mvn spring-boot:run
  3. Check discovery server: http://localhost:8761
  4. Call consumer service: http://localhost:9053/render

Conclusion

We demonstrated how to use Spring Cloud Eureka for service discovery. The client can invoke services without hardcoding addresses, relying on the discovery service to resolve them dynamically.

References

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