二、微服务客户端负载均衡之Ribbon

Ribbon简介

• Ribbon是Netflix发布的负载均衡器，它有助于控制 HTTP 和 TCP 的客户端的行为。为Ribbon配置服务提供者地址后，Ribbon就可基于某种负载均衡算法，自动地帮助服务消费者去请求。Ribbon默认为我们提供了很多负载均衡算法，例如轮询、随机等。当然，我们也可为 Ribbon 实现自定义的负载均衡算法。

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为服务消费者整合Ribbon

1. 启动一个Eureka注册中心，启动两个Eureka服务提供者(参考传送门);

2. 创建服务消费者，在pom文件中添加依赖:

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>

3. 创建启动类:

// 添加注解，使其具备负载均衡能力
@LoadBalanced
@Bean
public RestTemplate restTemplate() {
    return new RestTemplate();
}

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

4. 创建 Controller:

@RestController
public class MovieRibbonController {

    private static final Logger LOGGER = LoggerFactory.getLogger(MovieRibbonController.class);

    @Autowired
    private RestTemplate restTemplate;

    @Autowired
    private LoadBalancerClient loadBalancerClient;


    @GetMapping("/user/{id}")
    public User findById(@PathVariable Long id) {
        return this.restTemplate.getForObject("http://microservice-provider-user/" + id, User.class);
    }

    @GetMapping("/log-user-instance")
    public void logUserInstance() {
        ServiceInstance serviceInstance = this.loadBalancerClient.choose("microservice-provider-user");
        // 打印当前节点
        MovieRibbonController.LOGGER.info(
                "{}:{}:{}",
                serviceInstance.getServiceId(),
                serviceInstance.getHost(),
                serviceInstance.getPort());
    }
}

5. 多次访问http://127.0.0.1:8010/log-user-instance，返回结果:

INFO 11146 --- [nio-8010-exec-2] c.itmuch.consumer.MovieRibbonController  : microservice-provider-user:192.168.200.104:9000
INFO 11146 --- [nio-8010-exec-4] c.itmuch.consumer.MovieRibbonController  : microservice-provider-user:192.168.200.104:9001
INFO 11146 --- [nio-8010-exec-6] c.itmuch.consumer.MovieRibbonController  : microservice-provider-user:192.168.200.104:9000
INFO 11146 --- [nio-8010-exec-8] c.itmuch.consumer.MovieRibbonController  : microservice-provider-user:192.168.200.104:9001
INFO 11146 --- [io-8010-exec-10] c.itmuch.consumer.MovieRibbonController  : microservice-provider-user:192.168.200.104:9000
INFO 11146 --- [nio-8010-exec-2] c.itmuch.consumer.MovieRibbonController  : microservice-provider-user:192.168.200.104:9001
INFO 11146 --- [nio-8010-exec-4] c.itmuch.consumer.MovieRibbonController  : microservice-provider-user:192.168.200.104:9000
INFO 11146 --- [nio-8010-exec-7] c.itmuch.consumer.MovieRibbonController  : microservice-provider-user:192.168.200.104:9001
INFO 11146 --- [nio-8010-exec-9] c.itmuch.consumer.MovieRibbonController  : microservice-provider-user:192.168.200.104:9000

• 可以看到，请求会均匀分布到两个微服务节点上。
• 不能将restTemplate.getForObject(...)与loadBalancerClient.choose(...)写在一个方法中，两者会有冲突——restTemplate实际上是一个Ribbon客户端，本身包含choose的行为。

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Ribbon自定义配置

指定名称配置

1. 创建Ribbon配置类:

@Configuration
public class RibbonConfiguration {
    @Bean
    public IRule ribbonRule() {
        // 负载均衡改为随机
        return new RandomRule();
    }
}

2. 创建空类:

@Configuration
@RibbonClient(name = "microservice-provider-user",configuration = RibbonConfiguration.class)
public class TestConfiguration {

}

3. 多次访问http://127.0.0.1:8010/log-user-instance，返回结果:

INFO 11193 --- [nio-8010-exec-1] c.itmuch.consumer.MovieRibbonController  : microservice-provider-user:192.168.200.104:9000
INFO 11193 --- [nio-8010-exec-3] c.itmuch.consumer.MovieRibbonController  : microservice-provider-user:192.168.200.104:9000
INFO 11193 --- [nio-8010-exec-5] c.itmuch.consumer.MovieRibbonController  : microservice-provider-user:192.168.200.104:9001
INFO 11193 --- [nio-8010-exec-7] c.itmuch.consumer.MovieRibbonController  : microservice-provider-user:192.168.200.104:9000
INFO 11193 --- [nio-8010-exec-9] c.itmuch.consumer.MovieRibbonController  : microservice-provider-user:192.168.200.104:9001
INFO 11193 --- [nio-8010-exec-1] c.itmuch.consumer.MovieRibbonController  : microservice-provider-user:192.168.200.104:9000
INFO 11193 --- [nio-8010-exec-4] c.itmuch.consumer.MovieRibbonController  : microservice-provider-user:192.168.200.104:9001

全局配置

• 可使用@RibbonClients注解提供默认配置:

@RibbonClients
public class RibbonClientDefaultConfigurationTestsConfig {
    public static class BazServiceList extends ConfigurationBasedServerList {
        public BazServiceList(IClientConfig config) {
            super.initWithNiwsConfig(config);
        }
    }
}

class DefaultRibbonConfig {
    @Bean
    public IRule ribbonRule() {
        return new BestAvailableRule();
    }

    @Bean
    public IPing ribbonPing() {
        return new PingUrl();
    }

    @Bean
    public ServerList<Server> ribbonServerList(IClientConfig config) {
        return new RibbonClientDefaultConfigurationTestsConfig.BazServiceList(config);
    }

    @Bean
    public ServerListSubsetFilter serverListFilter() {
        return new ServerListSubsetFilter();
    }
}

使用属性自定义Ribbon配置

• NFLoadBalancerClassName: 配置ILoadBalancer的实现类。
• NFLoadBalancerRuleClassName: 配置IRule的实现类。
• NFLoadBalancerPingClassName: 配置IPing的实现类。
• NIWSServerListClassName: 配置ServerList的实现类。
• NIWSServerListFilterClassName: 配置ServerListFilter的实现类。

指定名称配置

microservice-provider-user:
  ribbon:
    NFLoadBalancerClassName: com.netflix.loadbalancer.RandomRule

全局配置

ribbon:
  NFLoadBalancerClassName: com.netflix.loadbalancer.RandomRule

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该文章摘自《Spring Cloud 与 Docker 微服务架构实战(第二版)》

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