Spring Cloud（七）：Zuul

比眉伴天荒 2021-10-01 11:12 266阅读 0赞

*  [Demo 源码下载][Demo]
 *  本案例为源码分支的 ribbon 分支

## Ribbon 简介 ##

*  分布式系统中，各个微服务会部署多个实例，**如何将服务消费者均匀分摊到多个服务提供者实例上，就要使用到负载均衡器。Ribbon 是负载均衡器**，它提供了很多负载均衡算法，例如轮询、随即等，在配置服务提供者地址后，可以将服务消费者请求均匀的分发

![9434708-82a9e1d3bc3a20be.png][]

Ribbon

## 快速入门-服务消费者整合 Ribbon ##

*  添加 Ribbon 依赖库

<dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-ribbobn</artifactId>
    </dependency>

*  给 RestTemplate 添加 @LoadBalaced 注解，就可整合 RestTemplate 和 Ribbon

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

*  修改Controller，请求地址修改为 [http://film-user/user/][http_film-user_user] ，**当 Ribbon 和 Eureka 配合使用时，会自动将虚拟主机名映射成微服务的网络地址，并注入了 LoadBalancerClient 输出当前选择的微服务节点**

@RestController
    public class MovieController {
        private final Logger log = LoggerFactory.getLogger(MovieController.class);
    
        @Autowired
        private RestTemplate restTemplate;
    
        @Autowired
        private LoadBalancerClient loadBalancerClient;
    
        @GetMapping("/user/{id}")
        public UserEntity findById(@PathVariable int id){
            return this.restTemplate.getForObject("http://film-user/"+id,UserEntity.class);
        }
    
        @GetMapping("/log-instance")
        public void logInstance(){
            ServiceInstance serviceInstance = this.loadBalancerClient.choose("film-user");
            log.info("{}:{}:{}",serviceInstance.getServiceId(),serviceInstance.getHost(),serviceInstance.getPort());
        }
    }

*  测试：
    
     *  启动 Eureka Server
     *  启动 2 至多个 film-user
     *  启动 flim-consumer
     *  访问 [http://localhost:8761/][http_localhost_8761] 查看微服务是否注册成功
     *  访问 [http://localhost:8010/user/1][http_localhost_8010_user_1] 会返回如下结果
    
        {"id":1,"username":"account1","name":"张三","age":20,"balance":100.00}
    
     *  多次访问 [http://localhost:8010/log-instance][http_localhost_8010_log-instance] 控制台会输出以下信息，可以看到请求会均匀的分布到两个服务提供者实例上
    
        2017-12-17 20:47:53.975  INFO 12313 --- [nio-8010-exec-2] com.linyuan.controller.MovieController   : flim-user:linyuandembp:8764
        2017-12-17 20:47:54.215  INFO 12313 --- [nio-8010-exec-1] com.linyuan.controller.MovieController   : flim-user:linyuandembp:8763
        2017-12-17 20:47:54.445  INFO 12313 --- [nio-8010-exec-3] com.linyuan.controller.MovieController   : flim-user:linyuandembp:8764
        2017-12-17 20:47:54.690  INFO 12313 --- [nio-8010-exec-4] com.linyuan.controller.MovieController   : flim-user:linyuandembp:8763
        2017-12-17 20:47:54.935  INFO 12313 --- [nio-8010-exec-5] com.linyuan.controller.MovieController   : flim-user:linyuandembp:8764
 *  **注意：不能将 restTemplate.getForObject(...) 与 loadBalancerClient.choose(...) 写在同一方法中，因为 rest-Template 实际上就是一个 Ribbon 客户端，本身已经包含“choose”行为**

## 配置 Ribbon ##

*  **Ribbon 的配置是细粒度的，不同的客户端可以使用不同的配置**

### 代码方式 ###

*  创建 Ribbon 配置类

/**
     * 该类为配置类
     * 不应该被ComponentScan扫描
     */
    @Configuration
    public class RibbonConfiguration {
        @Bean
        public IRule ribbonRule(){
            //配置负载均衡的规则，更改为随机
            return new RandomRule();
        }
    }

*  使用 @RibbonClient 或 @RibbonClients 注解为服务提供者指定配置类

@SpringBootApplication
    @EnableDiscoveryClient
    @RibbonClient(name = "flim-user",configuration = RibbonConfiguration.class)
    public class FlimConsumerApplication {
        @Bean
        @LoadBalanced
        public RestTemplate restTemplate(){
            return new RestTemplate();
        }
        public static void main(String[] args) {
            SpringApplication.run(FlimConsumerApplication.class, args);
        }
    }

*  访问测试地址 [http://localhost:8010/log-instance][http_localhost_8010_log-instance] 可看见请求会随机分布到两微服务上

2017-12-17 21:08:52.769  INFO 12524 --- [nio-8010-exec-7] com.linyuan.controller.MovieController   : flim-user:linyuandembp:8763
    2017-12-17 21:08:52.946  INFO 12524 --- [nio-8010-exec-8] com.linyuan.controller.MovieController   : flim-user:linyuandembp:8763
    2017-12-17 21:08:53.138  INFO 12524 --- [nio-8010-exec-9] com.linyuan.controller.MovieController   : flim-user:linyuandembp:8763
    2017-12-17 21:08:53.319  INFO 12524 --- [io-8010-exec-10] com.linyuan.controller.MovieController   : flim-user:linyuandembp:8764
    2017-12-17 21:08:53.511  INFO 12524 --- [nio-8010-exec-1] com.linyuan.controller.MovieController   : flim-user:linyuandembp:8763

*  **注意：RibbonConfiguration 类不能被 @ComponentScan 扫描到，否则配置信息就会被所有 @RibbonClient 共享，因此如果只想自定义某个 Ribbon 客户端的配置，必须防止被 @ComponentScan 扫描**

### 配置文件方式 ###

*  通过配置文件方式配置 Ribbon 更加方便，配置的前缀是 <clientName>.ribbon.
    
     *  **NFLoadBalancerClassName**：配置 ILoadBalancer 的实现类
     *  **NFLoadBalancerRuleClassName**：配置 IRule 的实现类
     *  **NFLoadBalancerPingClassName**：配置 IPing 实现类
     *  **NIWSServerListClassName**：配置 ServerList 的实现类
     *  **NIWSServerListFilterClassName**：配置 ServerListFilter 的实现类

flim-user:
      ribbon:
        NFLoadBalancerRuleClassName: com.netflix.loadbalancer.RandomRule

*  **还有常用的 Ribbon 全局配置**

ribbon:
        ConnectionTimeout: #连接超时时间
        ReadTimeout: #读取超时时间
        OkToRetryOnAllOperatotions: #对所有操作请求都进行重试
        MaxAutoRetriesNextServer:  #切换服务器实例的重试次数
        MaxAutoRetries:   #对当前实例的重试次数
        ServerListRefreshInterval:   #刷新服务列表源的间隔时间

[Demo]: https://link.jianshu.com?t=https%3A%2F%2Fgitee.com%2FLinYuanTongXue%2FDEMO-SPRING-CLOUD
[9434708-82a9e1d3bc3a20be.png]: /images/20210811/e67a4b1048bb4be08f0a0806317c8f62.png
[http_film-user_user]: https://link.jianshu.com?t=http%3A%2F%2Ffilm-user%2Fuser%2F
[http_localhost_8761]: https://link.jianshu.com?t=http%3A%2F%2Flocalhost%3A8761%2F
[http_localhost_8010_user_1]: https://link.jianshu.com?t=http%3A%2F%2Flocalhost%3A8010%2Fuser%2F1
[http_localhost_8010_log-instance]: https://link.jianshu.com?t=http%3A%2F%2Flocalhost%3A8010%2Flog-instance