Spring Cloud Ribbon is a client-side load balancing library built on top of Netflix Ribbon. It distributes incoming HTTP requests across multiple service instances registered in a service registry—such as Eureka—to prevent overloading any single node. When multiple replicas of a service (e.g., eureka-client-8762 and eureka-client-8763) are deployed and registered with Eureka, Ribbon transparently selects an appropriate instance for each outbound request using configurable strategies. Ribbon supports out-of-the-box algorithms—including round-robin (default), random, and weighted response time—and allows developers to plug in custom logic via implementations of IRule. #### 2. Integration Example

Project Setup

We assume two upstream services—user-service (running on ports 8762 and 8763)—are already registered in Eureka at http://localhost:8761/eureka. Now we build a consumer service named load-balancer-consumer (port 8764) that uses Ribbon to route requests. ##### Maven Depandencies

Add the following to pom.xml: ``` <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>

##### Configuration Fille

`application.yml`: ```
server:
  port: 8764

spring:
  application:
    name: load-balancer-consumer

eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka

Main Application Class

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

RestTemplate Configuration with Load Balancing

Create RestTemplateConfig.java under com.dzbiao.config: ``` @Configuration public class RestTemplateConfig {

@Bean
@LoadBalanced
public RestTemplate createBalancedClient() {
    return new RestTemplate();
}

}

##### Controller for Testing

In the same package as the main class, add: ```
@RestController
@RequestMapping("/api")
public class UserController {

    private final RestTemplate balancedClient;

    public UserController(RestTemplate balancedClient) {
        this.balancedClient = balancedClient;
    }

    @GetMapping("/user")
    public String fetchUserInfo() {
        // 'user-service' resolves to available Eureka instances
        return balancedClient.getForObject("http://user-service/user", String.class);
    }
}

Verification

After launching all four applications (Eureka server on 8761, two user-service instances on 8762/8763, and the consumre on 8764), access http://localhost:8764/api/user. Repeated calls will alternate responses indicating either 8762 or 8763, confirming round-robin distribution managed by Ribbon.