自定义Ribbon负载均衡

这里基于RandomRule修改

1. DeptConsumer80_App.java
   使用@RibbonClient对特定(name="MICROSERVICECLOUD-DEPT")的服务，指定特定(configuration = MyRibbonRule.class)的策略

@EnableEurekaClient
@SpringBootApplication
@RibbonClient(name = "MICROSERVICECLOUD-DEPT", configuration = MyRibbonRule.class)
public class DeptConsumer80_App {
    public static void main(String[] args) {
        SpringApplication.run(DeptConsumer80_App.class, args);
    }
}

2. MyRibbonRule.java
   警告：http://cloud.spring.io/spring-cloud-static/Greenwich.RELEASE/single/spring-cloud.html#_customizing_the_ribbon_client
   
   警告

简而言之就是，不能够与带有@ComponentScan或@SpringBootApplication注解的类，出现在同一包或其子包下。否则，会变成全局配置

@Configuration
public class MyRibbonRule {
    @Bean
    public IRule rule(){
        //return new RandomRule();
        return new MyRoundRule();
    }
}

工程结构图如下：

工程结构

3. MyRoundRule.java

/**
 * 基于RandomRule修改
 * 使用轮询的方式，每个实例调用5次
 * 然后再调用下一个实例
 */
public class MyRoundRule extends AbstractLoadBalancerRule {

    private int count = 0;//调用次数
    private int currentIndex = 0;//当前服务下标

    @SuppressWarnings({"RCN_REDUNDANT_NULLCHECK_OF_NULL_VALUE"})
    public Server choose(ILoadBalancer lb, Object key) {
        if (lb == null) {
            return null;
        } else {
            Server server = null;

            while(server == null) {
                if (Thread.interrupted()) {
                    return null;
                }

                List<Server> upList = lb.getReachableServers();
                List<Server> allList = lb.getAllServers();
                int serverCount = allList.size();
                if (serverCount == 0) {
                    return null;
                }

                //int index = this.rand.nextInt(serverCount);
                //server = (Server)upList.get(index);

                if(count < 5){
                    count++;
                    server = upList.get(currentIndex);
                }else {
                    count = 0;
                    currentIndex++;
                    if (currentIndex >= serverCount){
                        currentIndex = 0;
                    }
                }

                if (server == null) {
                    Thread.yield();
                } else {
                    if (server.isAlive()) {
                        return server;
                    }

                    server = null;
                    Thread.yield();
                }
            }

            return server;
        }
    }

    public Server choose(Object key) {
        return this.choose(this.getLoadBalancer(), key);
    }
    public void initWithNiwsConfig(IClientConfig clientConfig) {
    }
}