Service Discovery with Eureka

In a microservices architecture, multiple services interact with each other. Each service typically runs on a different host or port, which can change dynamically. Service Discovery solves the problem of how services can find each other in such an environment. Eureka, developed by Netflix, is one of the most popular tools for this purpose.

Eureka is a REST-based service that helps in the registration and discovery of services. It works as a service registry where all microservices can register themselves, and other services can discover and communicate with them easily. Eureka provides two main components:

• Eureka Server: Acts as a registry for all available services.
• Eureka Client: Registers with the Eureka Server and looks up other services.

Working of Eureka

• Service Registration: When a microservice starts, it registers itself with the Eureka Server, providing metadata such as service name, host, and port.
• Service Discovery: Other microservices that need to communicate with the registered service query the Eureka Server to find the service and its current location.
• Heartbeat Mechanism: Eureka clients send periodic heartbeats to the server to let it know that they are still alive. If the heartbeat is missed, the service is considered down.

Setting up Eureka in Spring Boot

• Add dependencies to your Spring Boot pom.xml for both the Eureka Server and Client.

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  <!-- Eureka Server Dependency --> <dependency>     <groupId>org.springframework.cloud</groupId>     <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId> </dependency>

• Enable Eureka Server in your main application class by adding @EnableEurekaServer.
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  @SpringBootApplication @EnableEurekaServer public class EurekaServerApplication {     public static void main(String[] args) {         SpringApplication.run(EurekaServerApplication.class, args);     } }

• Configure Eureka Client by adding the necessary properties in application.yml.
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  spring:   application:     name: service-name eureka:   client:     serviceUrl:       defaultZone: http://localhost:8761/eureka

• Start Eureka Server and clients. The Eureka dashboard at http://localhost:8761 will show all the registered services.

Benefits of Eureka

• Fault Tolerance: Eureka’s self-preservation mode ensures the system keeps running even if some services fail or stop sending heartbeats.
• Dynamic Scaling: Services can be added or removed without manually updating the configuration.
• Load Balancing: Eureka clients often integrate with load balancing tools like Ribbon, distributing requests evenly across available instances.