Spring Cloud Gateway Ribbon 自定义负载均衡

 依赖的spring cloud版本信息：

<parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.15.RELEASE</version>
    </parent>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Greenwich.SR5</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <dependency>
                <groupId>com.alibaba.cloud</groupId>
                <artifactId>spring-cloud-alibaba-dependencies</artifactId>
                <version>2.1.0.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

在微服务开发中，使用Spring Cloud Gateway做为服务的网关，网关后面启动N个业务服务。但是有这样一个需求，同一个用户的操作，有时候需要保证顺序性，如果使用默认负载均衡策略，同一个用户的请求可能会转发到不同的服务实例上面。所以需要实现一个负载均衡规则。

1，重写LoadBalancerClientFilter

import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR;
import java.net.URI;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;
import org.springframework.cloud.gateway.config.LoadBalancerProperties;
import org.springframework.cloud.gateway.filter.LoadBalancerClientFilter;
import org.springframework.cloud.netflix.ribbon.RibbonLoadBalancerClient;
import org.springframework.web.server.ServerWebExchange;

public class UserLoadBalancerClientFilter extends LoadBalancerClientFilter {

    public UserLoadBalancerClientFilter(LoadBalancerClient loadBalancer, LoadBalancerProperties properties) {
        super(loadBalancer, properties);
    }

    @Override
    protected ServiceInstance choose(ServerWebExchange exchange) {
        //这里可以拿到web请求的上下文，可以从header中取出来自己定义的数据。
        String userId = exchange.getRequest().getHeaders().getFirst("userId");
         if (userId == null) {
             return super.choose(exchange);
         }
        if (this.loadBalancer instanceof RibbonLoadBalancerClient) {
            RibbonLoadBalancerClient client = (RibbonLoadBalancerClient) this.loadBalancer;
            String serviceId = ((URI) exchange.getAttribute(GATEWAY_REQUEST_URL_ATTR)).getHost();
            //这里使用userId做为选择服务实例的key
            return client.choose(serviceId, userId);
        }
        return super.choose(exchange);
    }

}

 

2，添加自定义的负载规则

import java.util.List;
import org.apache.commons.lang.math.RandomUtils;
import com.netflix.client.config.IClientConfig;
import com.netflix.loadbalancer.AbstractLoadBalancerRule;
import com.netflix.loadbalancer.Server;

/**
 * 
 * @ClassName: GameCenterBalanceRule
 * @Description: 根据userId对服务进行负载均衡。同一个用户id的请求，都转发到同一个服务实例上面。
 * @author: wgs
 * @date: 2019年3月15日 下午2:17:06
 */
public class GameCenterBalanceRule extends AbstractLoadBalancerRule {

    @Override
    public Server choose(Object key) {//这里的key就是过滤器中传过来的userId

        List<Server> servers = this.getLoadBalancer().getReachableServers();
        if (servers.isEmpty()) {
            return null;
        }
        if (servers.size() == 1) {
            return servers.get(0);
        }
        if (key == null) {
            return randomChoose(servers);
        }
        return hashKeyChoose(servers, key);
    }
    /**
     * 
     * <p>Description:随机返回一个服务实例 </p>
     * @param servers
     * @return
     * @author wgs 
     * @date  2019年3月15日 下午2:25:23
     *
     */
    private Server randomChoose(List<Server> servers) {
        int randomIndex = RandomUtils.nextInt(servers.size());
        return servers.get(randomIndex);
    }
    /**
     * 
     * <p>Description:使用key的hash值，和服务实例数量求余，选择一个服务实例 </p>
     * @param servers
     * @param key
     * @return
     * @author wgs 
     * @date  2019年3月15日 下午2:25:36
     *
     */
    private Server hashKeyChoose(List<Server> servers, Object key) {
        int hashCode = Math.abs(key.hashCode());
        if (hashCode < servers.size()) {
            return servers.get(hashCode);
        }
        int index = hashCode % servers.size();
        return servers.get(index);

    }

    @Override
    public void initWithNiwsConfig(IClientConfig config) {

    }

}

 

3.  添加Bean

import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;
import org.springframework.cloud.gateway.config.LoadBalancerProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.client.RestTemplate;

@Configuration
public class LoadBalancedBean {

    @Bean
    @LoadBalanced
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }

    @Bean
    public UserLoadBalancerClientFilter userLoadBalanceClientFilter(LoadBalancerClient client, LoadBalancerProperties properties) {
        return new UserLoadBalancerClientFilter(client, properties);
    }
}

 

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