spring cloud中通过配置文件自定义Ribbon负载均衡策略

一、Ribbon中的负载均衡策略

1、Ribbon中支持的负载均衡策略

AvailabilityFilteringRule：过滤掉那些因为一直连接失败的被标记为circuit tripped的后端server，并过滤掉那些高并发的的后端server（active connections 超过配置的阈值） | 使用一个AvailabilityPredicate来包含过滤server的逻辑，其实就就是检查status里记录的各个server的运行状态

RandomRule：随机选择一个server

BestAvailabl：选择一个最小的并发请求的server，逐个考察Server，如果Server被tripped了，则忽略

RoundRobinRule：roundRobin方式轮询选择， 轮询index，选择index对应位置的server

WeightedResponseTimeRule：根据响应时间分配一个weight(权重)，响应时间越长，weight越小，被选中的可能性越低

RetryRule：对选定的负载均衡策略机上重试机制，在一个配置时间段内当选择server不成功，则一直尝试使用subRule的方式选择一个可用的server

ZoneAvoidanceRule：复合判断server所在区域的性能和server的可用性选择server

ResponseTimeWeightedRule：作用同WeightedResponseTimeRule，二者作用是一样的，ResponseTimeWeightedRule后来改名为WeightedResponseTimeRule

二、验证

1、自定义负载均衡策略

1. # 自定义负载均衡策略
   springboot-h2.ribbon.NFLoadBalancerRuleClassName=com.netflix.loadbalancer.RandomRule // 自定义使用随机策略，springboot-h2是服务应用名 

2、修改调用代码

package com.chhliu.springboot.restful.controller;  

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;  

import com.chhliu.springboot.restful.vo.User;  

@RestController
public class RestTemplateController {
    @Autowired
    private RestTemplate restTemplate;  

    @Autowired
    private LoadBalancerClient loadBalancerClient;  

    @GetMapping("/template/{id}")
    public User findById(@PathVariable Long id) {
        ServiceInstance serviceInstance = this.loadBalancerClient.choose("springboot-h2");
        System.out.println("===" + ":" + serviceInstance.getServiceId() + ":" + serviceInstance.getHost() + ":"
                + serviceInstance.getPort());// 打印当前调用服务的信息
        User u = this.restTemplate.getForObject("http://springboot-h2/user/" + id, User.class);
        System.out.println(u);
        return u;
    }
}  

3、测试

服务调用关系如下：

测试结果如下：

1. ===:springboot-h2:127.0.0.1:7902
   User [id=2, username=user2, name=李四, age=20, balance=100.00]
   ===:springboot-h2:127.0.0.1:7901
   User [id=2, username=user2, name=李四, age=20, balance=100.00]
   ===:springboot-h2:127.0.0.1:7902
   User [id=2, username=user2, name=李四, age=20, balance=100.00]
   ===:springboot-h2:127.0.0.1:7901
   User [id=2, username=user2, name=李四, age=20, balance=100.00]
   ===:springboot-h2:127.0.0.1:7902
   User [id=2, username=user2, name=李四, age=20, balance=100.00]
   ===:springboot-h2:127.0.0.1:7902
   User [id=2, username=user2, name=李四, age=20, balance=100.00]
   ===:springboot-h2:127.0.0.1:7902
   User [id=2, username=user2, name=李四, age=20, balance=100.00]
   ===:springboot-h2:127.0.0.1:7902
   User [id=2, username=user2, name=李四, age=20, balance=100.00]
   ===:springboot-h2:127.0.0.1:7902
   User [id=2, username=user2, name=李四, age=20, balance=100.00]
   ===:springboot-h2:127.0.0.1:7901
   User [id=2, username=user2, name=李四, age=20, balance=100.00]
   ===:springboot-h2:127.0.0.1:7901
   User [id=2, username=user2, name=李四, age=20, balance=100.00]
   ===:springboot-h2:127.0.0.1:7902
   User [id=2, username=user2, name=李四, age=20, balance=100.00]
   ===:springboot-h2:127.0.0.1:7902
   User [id=2, username=user2, name=李四, age=20, balance=100.00]
   ===:springboot-h2:127.0.0.1:7901
   User [id=2, username=user2, name=李四, age=20, balance=100.00]
   ===:springboot-h2:127.0.0.1:7901
   User [id=2, username=user2, name=李四, age=20, balance=100.00]
   发现选择7901端口服务和7902端口服务确实是随机的！