前言
spring-cloud-starter-netflix-ribbon已经不再更新了，最新版本是2.2.10.RELEASE，最后更新时间是2021年11月18日，详细信息可以看maven官方仓库：https://search.maven.org/artifact/org.springframework.cloud/spring-cloud-starter-netflix-ribbon，SpringCloud官方推荐使用spring-cloud-starter-loadbalancer进行负载均衡。我们在开发的时候，多人开发同一个微服务，都注册到同一个nacos，前端请求的时候，网关Gateway默认轮训请求注册中心的服务，OpenFeign也会轮询请求注册中心的服务，这样就会导致前端有时会无法请求到我们本地写的接口，而是请求到别人的服务中。所以我们可以重写Loadbalancer默认的负载均衡策略，实现自定义负载均衡策略，不管是Gateway还是OpenFeign都只能请求到我们自己本地的服务。
我的版本如下：
一、添加负载方式配置
1、定义负载均衡方式的枚举
public enum LoadBalancerTypeEnum { DEV, GATEWAY, ROUND_ROBIN, RANDOM;}2、添加配置类，默认使用轮训方式
import lombok.Data;import org.springframework.boot.context.properties.ConfigurationProperties;@Data@ConfigurationProperties(prefix = "spring.cloud.loadbalancer")public class LoadBalanceProperties { private LoadBalancerTypeEnum type = LoadBalancerTypeEnum.ROUND_ROBIN;}二、参考默认实现自定义
默认的负载均衡策略是这个类：
org.springframework.cloud.loadbalancer.core.RoundRobinLoadBalancer
我们参考这个类实现自己的负载均衡策略即可，RoundRobinLoadBalancer实现了ReactorServiceInstanceLoadBalancer这个接口，实现了choose这个方法，如下图：
在choose方法中调用了processInstanceResponse方法，processInstanceResponse方法中调用了getInstanceResponse方法，所以我们我们可以复制RoundRobinLoadBalancer整个类，只修改getInstanceResponse这个方法里的内容就可以实现自定义负载均衡策略。
在自定义的类中，我们实现了四种负载均衡策略
1、getRoundRobinInstance方法是直接复制的RoundRobinLoadBalancer类中的实现；
2、getRandomInstance方法参考org.springframework.cloud.loadbalancer.core.RandomLoadBalancer类中的实现；
3、getDevelopmentInstance方法是返回所有服务中和当前机器ip一致的服务，如果没有，则轮训返回；
4、getGatewayDevelopmentInstance方法是返回所有服务中和网关请求头中ip一致的服务。
import cn.hutool.core.convert.Convert;import cn.hutool.core.lang.TypeReference;import com.ruoyi.common.core.utils.StringUtils;import com.ruoyi.common.core.utils.ip.IpUtils;import com.ruoyi.common.loadbalance.config.LoadBalancerTypeEnum;import lombok.extern.slf4j.Slf4j;import org.springframework.beans.factory.ObjectProvider;import org.springframework.cloud.client.ServiceInstance;import org.springframework.cloud.client.loadbalancer.DefaultRequest;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.RequestData;import org.springframework.cloud.client.loadbalancer.RequestDataContext;import org.springframework.cloud.client.loadbalancer.Response;import org.springframework.cloud.loadbalancer.core.NoopServiceInstanceListSupplier;import org.springframework.cloud.loadbalancer.core.ReactorServiceInstanceLoadBalancer;import org.springframework.cloud.loadbalancer.core.SelectedInstanceCallback;import org.springframework.cloud.loadbalancer.core.ServiceInstanceListSupplier;import org.springframework.http.HttpHeaders;import reactor.core.publisher.Mono;import java.util.List;import java.util.Objects;import java.util.Random;import java.util.concurrent.ThreadLocalRandom;import java.util.concurrent.atomic.AtomicInteger;@Slf4jpublic class CustomSpringCloudLoadBalancer implements ReactorServiceInstanceLoadBalancer { private final String serviceId; private final AtomicInteger position; private final LoadBalancerTypeEnum type; private final ObjectProvider serviceInstanceListSupplierProvider; public CustomSpringCloudLoadBalancer(String serviceId, LoadBalancerTypeEnum type, ObjectProvider serviceInstanceListSupplierProvider) { this(serviceId, new Random().nextInt(1000), type, serviceInstanceListSupplierProvider); } public CustomSpringCloudLoadBalancer(String serviceId, int seedPosition, LoadBalancerTypeEnum type, ObjectProvider serviceInstanceListSupplierProvider) { this.serviceId = serviceId; this.position = new AtomicInteger(seedPosition); this.type = type; this.serviceInstanceListSupplierProvider = serviceInstanceListSupplierProvider; } @Override public Mono> choose(Request request) { ServiceInstanceListSupplier supplier = serviceInstanceListSupplierProvider.getIfAvailable(NoopServiceInstanceListSupplier::new); return supplier.get(request).next().map(serviceInstances -> processInstanceResponse(request, supplier, serviceInstances)); } private Response processInstanceResponse(Request request, ServiceInstanceListSupplier supplier, List serviceInstances) { Response serviceInstanceResponse = getInstanceResponse(request, serviceInstances); if (supplier instanceof SelectedInstanceCallback && serviceInstanceResponse.hasServer()) { ((SelectedInstanceCallback) supplier).selectedServiceInstance(serviceInstanceResponse.getServer()); } return serviceInstanceResponse; } private Response getInstanceResponse(Request request, List instances) { if (instances.isEmpty()) { if (log.isWarnEnabled()) { log.warn("No servers available for service: " + serviceId); } return new EmptyResponse(); } if (Objects.equals(type, LoadBalancerTypeEnum.ROUND_ROBIN)){ return this.getRoundRobinInstance(instances); }else if (Objects.equals(type, LoadBalancerTypeEnum.RANDOM)){ return this.getRandomInstance(instances); }else if (Objects.equals(type, LoadBalancerTypeEnum.DEV)){ return this.getDevelopmentInstance(instances); }else if (Objects.equals(type, LoadBalancerTypeEnum.GATEWAY)){ return this.getGatewayDevelopmentInstance(request, instances); } return this.getRoundRobinInstance(instances); } private Response getGatewayDevelopmentInstance(Request request, List instances) { //把request转为默认的DefaultRequest，从request中拿到请求的ip信息，再选择ip一样的微服务 DefaultRequest defaultRequest = Convert.convert(new TypeReference>() {}, request); RequestDataContext context = defaultRequest.getContext(); RequestData clientRequest = context.getClientRequest(); HttpHeaders headers = clientRequest.getHeaders(); String requestIp = IpUtils.getIpAddressFromHttpHeaders(headers); log.debug("客户端请求gateway的ip:{}", requestIp); //先取得和本地ip一样的服务，如果没有则按默认来取 for (ServiceInstance instance : instances) { String currentServiceId = instance.getServiceId(); String host = instance.getHost(); log.debug("注册服务：{}，ip：{}", currentServiceId, host); if (StringUtils.isNotEmpty(host) && StringUtils.equals(requestIp, host)) { return new DefaultResponse(instance); } } return getRoundRobinInstance(instances); } private Response getDevelopmentInstance(List instances) { //获取本机ip String hostIp = IpUtils.getHostIp(); log.debug("本机Ip:{}", hostIp); //先取得和本地ip一样的服务，如果没有则按默认来取 for (ServiceInstance instance : instances) { String currentServiceId = instance.getServiceId(); String host = instance.getHost(); log.debug("注册服务：{}，ip：{}", currentServiceId, host); if (StringUtils.isNotEmpty(host) && StringUtils.equals(hostIp, host)) { return new DefaultResponse(instance); } } return getRoundRobinInstance(instances); } private Response getRandomInstance(List instances) { int index = ThreadLocalRandom.current().nextInt(instances.size()); ServiceInstance instance = instances.get(index); return new DefaultResponse(instance); } private Response getRoundRobinInstance(List instances) { // 每一次计数器都自动+1，实现轮询的效果 int pos = this.position.incrementAndGet() & Integer.MAX_VALUE; ServiceInstance instance = instances.get(pos % instances.size()); return new DefaultResponse(instance); }} 其中的工具类如下：
import java.net.InetAddress;import java.net.URL;import java.net.UnknownHostException;import java.util.List;import java.util.Objects;import javax.servlet.http.HttpServletRequest;import cn.hutool.core.collection.CollectionUtil;import cn.hutool.core.util.URLUtil;import org.springframework.http.HttpHeaders;public class IpUtils{ public static String getHostIp(){ try{ return InetAddress.getLocalHost().getHostAddress(); }catch (UnknownHostException e){ } return "127.0.0.1"; } public static String getIpAddressFromHttpHeaders(HttpHeaders httpHeaders){ if (httpHeaders == null){ return "unknown"; } //前端请求自定义请求头，转发到哪个服务 List ipList = httpHeaders.get("forward-to"); String ip = CollectionUtil.get(ipList, 0); //请求自带的请求头 if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)){ ipList = httpHeaders.get("x-forwarded-for"); ip = CollectionUtil.get(ipList, 0); } //从referer获取请求的ip地址 if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)){ //从referer中获取请求的ip地址 List refererList = httpHeaders.get("referer"); String referer = CollectionUtil.get(refererList, 0); URL url = URLUtil.url(referer); if (Objects.nonNull(url)){ ip = url.getHost(); }else { ip = "unknown"; } } if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)){ ipList = httpHeaders.get("Proxy-Client-IP"); ip = CollectionUtil.get(ipList, 0); } if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)){ ipList = httpHeaders.get("X-Forwarded-For"); ip = CollectionUtil.get(ipList, 0); } if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)){ ipList = httpHeaders.get("WL-Proxy-Client-IP"); ip = CollectionUtil.get(ipList, 0); } if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)){ ipList = httpHeaders.get("X-Real-IP"); ip = CollectionUtil.get(ipList, 0); } return "0:0:0:0:0:0:0:1".equals(ip) ? "127.0.0.1" : getMultistageReverseProxyIp(ip); }} getIpAddressFromHttpHeaders方法中，是从请求头总拿到了自定义的请求头forward-to，要想实现此功能，就需要前端发送请求的时候携带这个请求头，例如
在若依的request.js中可以这么写： config.headers['forward-to'] = '192.168.0.145'
三、配置负载均衡策略
默认的配置在这里：
org.springframework.cloud.loadbalancer.annotation.LoadBalancerClientConfiguration
我们参考这个配置，实现自己的配置。启用上面写好的配置类LoadBalanceProperties，然后传到自定义的负载均衡策略类CustomSpringCloudLoadBalancer，其他的复制就可以。
import com.ruoyi.common.loadbalance.core.CustomSpringCloudLoadBalancer;import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;import org.springframework.boot.context.properties.EnableConfigurationProperties;import org.springframework.cloud.client.ServiceInstance;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.context.annotation.Configuration;import org.springframework.core.env.Environment;@SuppressWarnings("all")@Configuration(proxyBeanMethods = false)@EnableConfigurationProperties(LoadBalanceProperties.class)public class CustomLoadBalanceClientConfiguration { @Bean @ConditionalOnBean(LoadBalancerClientFactory.class) public ReactorLoadBalancer customLoadBalancer(LoadBalanceProperties loadBalanceProperties, Environment environment, LoadBalancerClientFactory loadBalancerClientFactory) { String name = environment.getProperty(LoadBalancerClientFactory.PROPERTY_NAME); return new CustomSpringCloudLoadBalancer(name, loadBalanceProperties.getType(), loadBalancerClientFactory.getLazyProvider(name, ServiceInstanceListSupplier.class)); }} 然后使用LoadBalancerClients注解加载一下配置
import org.springframework.cloud.loadbalancer.annotation.LoadBalancerClients;@LoadBalancerClients(defaultConfiguration = CustomLoadBalanceClientConfiguration.class)public class CustomLoadBalanceAutoConfiguration {}四、使用
将以上代码独立成一个模块，然后再其他微服务中的pom文件中引入，然后添加对应的配置就可以实现自定义负载均衡了
1、在微服务中配置如下即可实现调用其他服务时，调用自己本地开发环境的微服务
spring.cloud.loadbalancer.type=dev
2、在网关中配置如下即可实现调用固定某个服务
spring.cloud.loadbalancer.type=gateway
写在最后的话
最开始只有想法，但是不知道怎么实现，百度也没找到合适的方案。所以就开始看源码，研究了一下，然后照着源码写，测试了一下真的就实现了。所以，多看看源码还是有好处的。
来源地址：https://blog.csdn.net/WayneLee0809/article/details/128557770
