Spring Cloud Eureka Tutorial

Overview

Spring Cloud Eureka is a service discovery tool that helps in locating services in a microservices architecture. It allows services to register themselves and discover other services without hardcoding their locations.

Key Features of Spring Cloud Eureka

Spring Cloud Eureka offers several features that facilitate building and deploying microservices:

• Service Registration: Allows services to register themselves with the Eureka server.
• Service Discovery: Enables services to discover other services registered with the Eureka server.
• Health Checks: Monitors the health status of services and removes unhealthy instances.
• Load Balancing: Distributes requests across multiple instances of a service.

Setting Up Eureka Server

To set up a Eureka server, follow these steps:

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

// application.properties
server.port=8761
eureka.client.register-with-eureka=false
eureka.client.fetch-registry=false

The application.properties file configures the server to run on port 8761 and disables its own registration with Eureka.

Setting Up Eureka Client

To set up a Eureka client, follow these steps:

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

// application.properties
eureka.client.service-url.defaultZone=http://localhost:8761/eureka/
spring.application.name=eureka-client

The application.properties file configures the client to connect to the Eureka server and sets the application name.

Service Registration and Discovery

Once the Eureka client is configured, it will automatically register itself with the Eureka server and can discover other registered services.

// ExampleService.java
@Service
public class ExampleService {
    private final RestTemplate restTemplate;

    @Autowired
    public ExampleService(RestTemplate restTemplate) {
        this.restTemplate = restTemplate;
    }

    public String callAnotherService() {
        return restTemplate.getForObject("http://another-service/endpoint", String.class);
    }
}

// RestTemplateConfig.java
@Configuration
public class RestTemplateConfig {
    @Bean
    @LoadBalanced
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

In this example, the ExampleService class uses a load-balanced RestTemplate to call another service registered with Eureka.

Health Checks

Eureka can perform health checks on registered services to ensure they are healthy. Add the Spring Boot Actuator dependency to enable health checks:

// build.gradle
dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-actuator'
}

// application.properties
management.endpoints.web.exposure.include=health,info

The application.properties file configures the Actuator to expose health and info endpoints.

Key Points

Conclusion

Spring Cloud Eureka is a powerful tool for service discovery and registration in a microservices architecture. By leveraging its features, developers can build scalable and resilient microservices that can easily discover and communicate with each other. Happy coding!