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：

<spring-boot.version>2.7.3</spring-boot.version>
<spring-cloud.version>2021.0.4</spring-cloud.version>
<spring-cloud-alibaba.version>2021.0.4.0</spring-cloud-alibaba.version>

一、添加负载方式配置

1、定义负载均衡方式的枚举

public enum LoadBalancerTypeEnum {

    /**
     * 开发环境，获取自己的服务
     */
    DEV,

    /**
     * 网关，根据请求地址获取对应的服务
     */
    GATEWAY,

    /**
     * 轮循
     */
    ROUND_ROBIN,

    /**
     * 随机
     */
    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;

/**
 * 负载均衡配置项
 */
@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;

/**
 * 自定义 SpringCloud 负载均衡算法
 * 负载均衡算法的默认实现是 {@link org.springframework.cloud.loadbalancer.core.RoundRobinLoadBalancer}
 *
 */
@Slf4j
public class CustomSpringCloudLoadBalancer implements ReactorServiceInstanceLoadBalancer {

    private final String serviceId;
    private final AtomicInteger position;
    private final LoadBalancerTypeEnum type;
    private final ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider;

    public CustomSpringCloudLoadBalancer(String serviceId,
                                         LoadBalancerTypeEnum type,
                                         ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider) {
        this(serviceId, new Random().nextInt(1000), type, serviceInstanceListSupplierProvider);
    }

    public CustomSpringCloudLoadBalancer(String serviceId,
                                         int seedPosition,
                                         LoadBalancerTypeEnum type,
                                         ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider) {
        this.serviceId = serviceId;
        this.position = new AtomicInteger(seedPosition);
        this.type = type;
        this.serviceInstanceListSupplierProvider = serviceInstanceListSupplierProvider;
    }

    @Override
    public Mono<Response<ServiceInstance>> choose(Request request) {
        ServiceInstanceListSupplier supplier = serviceInstanceListSupplierProvider.getIfAvailable(NoopServiceInstanceListSupplier::new);
        return supplier.get(request).next().map(serviceInstances -> processInstanceResponse(request, supplier, serviceInstances));
    }

    private Response<ServiceInstance> processInstanceResponse(Request request,
                                                              ServiceInstanceListSupplier supplier,
                                                              List<ServiceInstance> serviceInstances) {
        Response<ServiceInstance> serviceInstanceResponse = getInstanceResponse(request, serviceInstances);
        if (supplier instanceof SelectedInstanceCallback && serviceInstanceResponse.hasServer()) {
            ((SelectedInstanceCallback) supplier).selectedServiceInstance(serviceInstanceResponse.getServer());
        }
        return serviceInstanceResponse;
    }

    private Response<ServiceInstance> getInstanceResponse(Request request, List<ServiceInstance> 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);
    }

    /**
     * 获取网关本机实例
     *
     * @param instances 实例
     * @return {@link Response }<{@link ServiceInstance }>
     * @author : lwq
     * @date : 2022-12-15 14:22:13
     */
    private Response<ServiceInstance> getGatewayDevelopmentInstance(Request request, List<ServiceInstance> 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<RequestDataContext> defaultRequest = Convert.convert(new TypeReference<DefaultRequest<RequestDataContext>>() {}, 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);
    }


    /**
     * 获取本机实例
     *
     * @param instances 实例
     * @return {@link Response }<{@link ServiceInstance }>
     * @author : lwq
     * @date : 2022-12-15 14:22:13
     */
    private Response<ServiceInstance> getDevelopmentInstance(List<ServiceInstance> 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);
    }

    /**
     * 使用随机算法
     * 参考{link {@link org.springframework.cloud.loadbalancer.core.RandomLoadBalancer}}
     *
     * @param instances 实例
     * @return {@link Response }<{@link ServiceInstance }>
     * @author : lwq
     * @date : 2022-12-15 13:32:11
     */
    private Response<ServiceInstance> getRandomInstance(List<ServiceInstance> instances) {
        int index = ThreadLocalRandom.current().nextInt(instances.size());
        ServiceInstance instance = instances.get(index);
        return new DefaultResponse(instance);
    }

    /**
     * 使用RoundRobin机制获取节点
     *
     * @param instances 实例
     * @return {@link Response }<{@link ServiceInstance }>
     * @author : lwq
     * @date : 2022-12-15 13:28:31
     */
    private Response<ServiceInstance> getRoundRobinInstance(List<ServiceInstance> 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;

/**
 * 获取IP方法
 */
public class IpUtils{

    /**
     * 获取IP地址
     *
     * @return 本地IP地址
     */
    public static String getHostIp(){
        try{
            return InetAddress.getLocalHost().getHostAddress();
        }catch (UnknownHostException e){
        }
        return "127.0.0.1";
    }

    /**
     * 获取客户端IP
     *
     * @param httpHeaders 请求头
     * @return IP地址
     */
    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<String> 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<String> 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;

/**
 * 自定义负载均衡客户端配置
 *
 */
@SuppressWarnings("all")
@Configuration(proxyBeanMethods = false)
@EnableConfigurationProperties(LoadBalanceProperties.class)
public class CustomLoadBalanceClientConfiguration {

    @Bean
    @ConditionalOnBean(LoadBalancerClientFactory.class)
    public ReactorLoadBalancer<ServiceInstance> 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;

/**
 * 自定义负载均衡自动配置
 *
 */
@LoadBalancerClients(defaultConfiguration = CustomLoadBalanceClientConfiguration.class)
public class CustomLoadBalanceAutoConfiguration {

}