spring cloud 2020.0.1 LoadBalancer负载均衡算法切换

淩亂°似流年 2022-11-06 06:53 54阅读 0赞

## 0、前言 ##

这是学习尚硅谷 spring cloud中遇到的一个坑 多看文档地址：\[文档地址\]\[https://docs.spring.io/spring-cloud-commons/docs/current/reference/html/\#custom-loadbalancer-configuration\]

## 1、spring cloud 2020.0.1 LoadBalancer负载均衡算法切换 ##

springcloud 2020.0.1 版本之后 删除了eureka中的ribbon，替代ribbon的是spring cloud自带的LoadBalancer，默认使用的是轮询的方式

如果切换，需要我们进行配置

我们这里使用的是restTemplate作为访问工具

### 1.1 首先定义一个CustomLoadBalancerConfiguration.class 这个包可以在主启动类所在包及其子包下 这一点和ribbon不同 ###

package com.peach.springcloud.config;
    
    import org.springframework.cloud.client.ServiceInstance;
    import org.springframework.cloud.loadbalancer.core.RandomLoadBalancer;
    import org.springframework.cloud.loadbalancer.core.ReactorLoadBalancer;
    import org.springframework.cloud.loadbalancer.core.ServiceInstanceListSupplier;
    import org.springframework.cloud.loadbalancer.support.LoadBalancerClientFactory;
    import org.springframework.context.annotation.Bean;
    import org.springframework.core.env.Environment;
    
    //这里 不需要 @configuration注解  不需要 不需要
    public class CustomLoadBalancerConfiguration {
    
        @Bean
        ReactorLoadBalancer<ServiceInstance> randomLoadBalancer(Environment environment,
                                                                LoadBalancerClientFactory loadBalancerClientFactory) {
            String name = environment.getProperty(LoadBalancerClientFactory.PROPERTY_NAME);
    
            return new RandomLoadBalancer(loadBalancerClientFactory
                    .getLazyProvider(name, ServiceInstanceListSupplier.class),
                    name);
        }
    }

### 1.2 之后在我们注入restTemplate的地方使用注解@LoadBalancerClients 或者@LoadBalancerClient注解进行配置 ###

package com.peach.springcloud.config;
    
    import org.springframework.cloud.client.loadbalancer.LoadBalanced;
    import org.springframework.cloud.loadbalancer.annotation.LoadBalancerClient;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    import org.springframework.web.client.RestTemplate;
    
    @Configuration
    //在这里配置我们自定义的LoadBalancer策略 如果有大佬想自己扩展算法 需要实现ReactorServiceInstanceLoadBalancer接口
    //@LoadBalancerClients(defaultConfiguration = {name = "CLOUD-PAYMENT-SERVICE", configuration = CustomLoadBalancerConfiguration.class})
    //注意这里的name属性 需要和eureka页面中的服务提供者名字一直 此时页面中是大写
    @LoadBalancerClient(name = "CLOUD-PAYMENT-SERVICE",configuration = CustomLoadBalancerConfiguration.class)
    public class ApplicationContextConfig {
    
        //将这个对象放入ioc容器
        @Bean
        @LoadBalanced  //使用这个注解给restTemplate赋予了负载均衡的能力
        public RestTemplate getRestTemplate(){
            return new RestTemplate();
        }
    }

注意@LoadBalancerClients 或者@LoadBalancerClient注解中的name或者value属性一定要和eureka中注册的服务名一致 大小写一定要一致

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM1Nzk5NjY4_size_16_color_FFFFFF_t_70_pic_center]

### 1.3 之后访问页面就可以看到了 ###

### 1.4 自定义负载均衡算法 ###

我的做法很简单 看源码的RoundRobinLoadBalancer的实现 copy一下在最后选择的时候改变一下策略即可 看下面代码中的注释

package com.peach.springcloud.config;
    
    import org.apache.commons.logging.Log;
    import org.apache.commons.logging.LogFactory;
    import org.springframework.beans.factory.ObjectProvider;
    import org.springframework.cloud.client.ServiceInstance;
    import org.springframework.cloud.client.loadbalancer.DefaultResponse;
    import org.springframework.cloud.client.loadbalancer.EmptyResponse;
    import org.springframework.cloud.client.loadbalancer.Request;
    import org.springframework.cloud.client.loadbalancer.Response;
    import org.springframework.cloud.loadbalancer.core.*;
    import reactor.core.publisher.Mono;
    
    import java.util.List;
    import java.util.Random;
    import java.util.concurrent.atomic.AtomicInteger;
    
    //这个方法基本是copy的RoundRobinLoadBalancer自己改一改出来的
    public class PeachLoadBalancer implements ReactorServiceInstanceLoadBalancer {
        private static final Log log = LogFactory.getLog(RoundRobinLoadBalancer.class);
    
        final AtomicInteger position;//请求的次数
    
        final String serviceId; //服务名称 用于提示报错信息的
    
        private int flag = 0; //自己定义的计数器
    
        //两个参数的构造方法 需要服务名称和实例提供者 这个在方法中传递进来
        public PeachLoadBalancer(ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider,
                                      String serviceId) {
            //如果不传人请求次数就自己初始化 反正每次都+1
            this(new Random().nextInt(1000), serviceId,serviceInstanceListSupplierProvider);
        }
    
        public PeachLoadBalancer(int seedPosition, String serviceId, ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider) {
            this.position = new AtomicInteger(seedPosition);
            this.serviceId = serviceId;
            this.serviceInstanceListSupplierProvider = serviceInstanceListSupplierProvider;
        }
    
        ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider;
        @Override
        public Mono<Response<ServiceInstance>> choose(Request request) {
            //从服务提供者中获取到当前request请求中的serviceInstances并且遍历
            ServiceInstanceListSupplier supplier = serviceInstanceListSupplierProvider
                    .getIfAvailable(NoopServiceInstanceListSupplier::new);
            return supplier.get(request).next()
                    .map(serviceInstances -> processInstanceResponse(supplier, serviceInstances));
        }
    
        private Response<ServiceInstance> processInstanceResponse(ServiceInstanceListSupplier supplier,
                                                                  List<ServiceInstance> serviceInstances) {
            Response<ServiceInstance> serviceInstanceResponse = getInstanceResponse(serviceInstances);
            if (supplier instanceof SelectedInstanceCallback && serviceInstanceResponse.hasServer()) {
                ((SelectedInstanceCallback) supplier).selectedServiceInstance(serviceInstanceResponse.getServer());
            }
            return serviceInstanceResponse;
        }
    
        private Response<ServiceInstance> getInstanceResponse(List<ServiceInstance> instances) {
            if (instances.isEmpty()) {
                if (log.isWarnEnabled()) {
                    log.warn("No servers available for service: " + serviceId);
                }
                return new EmptyResponse();
            }
            //pos是当前请求的次数 这样可以自定义负载均衡的切换  这个每次+1的操作是复制的 最好是不删
            int pos = Math.abs(this.position.incrementAndGet());
    
            if (pos%4==0){
                //是4的倍数就切换
                flag += 1;
            }
            if (flag >= instances.size()){
                flag = 0;
            }
            //主要的就是这句代码设置负载均衡切换
            ServiceInstance instance = instances.get(flag);
            return new DefaultResponse(instance);
        }
    }

### 1.5之后在配置的地方也就是CustomLoadBalancerConfiguration配置类中返回我们自己的方案即可 ###

package com.peach.springcloud.config;
    
    import org.springframework.cloud.client.ServiceInstance;
    import org.springframework.cloud.loadbalancer.core.RandomLoadBalancer;
    import org.springframework.cloud.loadbalancer.core.ReactorLoadBalancer;
    import org.springframework.cloud.loadbalancer.core.ServiceInstanceListSupplier;
    import org.springframework.cloud.loadbalancer.support.LoadBalancerClientFactory;
    import org.springframework.context.annotation.Bean;
    import org.springframework.core.env.Environment;
    
    public class CustomLoadBalancerConfiguration {
    
        @Bean
        ReactorLoadBalancer<ServiceInstance> randomLoadBalancer(Environment environment,
                                                                LoadBalancerClientFactory loadBalancerClientFactory) {
            String name = environment.getProperty(LoadBalancerClientFactory.PROPERTY_NAME);
    
    //        这里返回了新的randomLoadBalancer
    
            //这里返回了我自己定义的方法
            return new PeachLoadBalancer(loadBalancerClientFactory.getLazyProvider(name, ServiceInstanceListSupplier.class), name);
    //        return new RandomLoadBalancer(loadBalancerClientFactory
    //                .getLazyProvider(name, ServiceInstanceListSupplier.class),
    //                name);
        }
    }

### 1.6 之后访问页面就可以看到了 ###

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