Microservice Components: Load Balancing Ribbon

1. Introduction of Ribbon

In microservices, usually an application system needs to deploy multiple instances, which are distributed in different running containers. In order to avoid all requests being concentrated on one machine, so that requests are evenly distributed on multiple instance application systems, the load balancing component Ribbon is needed at this time.

2. Ribbon use

2-1 Start the eureka registry

@SpringBootApplication
@EnableEurekaServer
public class EurekaApplication {

    public static void main(String[] args) {
        SpringApplication.run(EurekaApplication.class, args);
    }
}

Start springboot-eureka-peer1

server.port=8761

spring.application.name=springboot-eureka-peer1

eureka.instance.hostname=localhost
eureka.client.serviceUrl.defaultZone=http://localhost:8762/eureka/,http://localhost:8761/eureka/

Start springboot-eureka-peer2

server.port=8762

spring.application.name=springboot-eureka-peer2

eureka.instance.hostname=localhost
eureka.client.serviceUrl.defaultZone=http://localhost:8761/eureka/,http://localhost:8762/eureka/

2-2 Start the service provider

java -jar -Dserver.port=8071 microservice-provider-user-0.0.1-SNAPSHOT.jar
java -jar -Dserver.port=8072 microservice-provider-user-0.0.1-SNAPSHOT.jar

2-3 View service registration status

http://mengka-host.local:8762/

2-4 Start the service call client

/**
   * Instantiate RestTemplate and enable load balancing capability through @LoadBalanced annotation.
   * @return restTemplate
   */
  @Bean
  @LoadBalanced
  public RestTemplate restTemplate() {
    return new RestTemplate();
  }

@Service
public class RibbonService {
  @Autowired
  private RestTemplate restTemplate;

  public User findById(Long id) {
    // http://serviceId/url of the service provider
    return this.restTemplate.getForObject("http://microservice-provider-user/" + id, User.class);
  }
}

eureka.client.serviceUrl.defaultZone=http://localhost:8761/eureka/,http://localhost:8762/eureka/

2-5 Call the findById interface service

http://127.0.0.1:8010/ribbon/1

Service calls are evenly distributed across 2 service provider machines:

3. Feign use

Feign is a declarative, templated HTTP client. Spring cloud adds annotation support to Feign, and integrates Ribbon and Eureka to provide load balancing, making it easier to write service invocation clients.

3-1 Start the service call client

使用@EnableFeignClients开启Feign

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

服务调用接口

@FeignClient(name = "microservice-provider-user")
public interface UserFeignClient {
  @RequestMapping("/{id}")
  public User findByIdFeign(@RequestParam("id") Long id);
}

eureka.client.serviceUrl.defaultZone=http://localhost:8761/eureka/,http://localhost:8762/eureka/

3-2 调用findById接口服务

http://127.0.0.1:8020/feign/2

服务调用均衡分布在2台服务提供者机器上：