自定义基于一致性哈希负载均衡策略的实现

秒速五厘米 2023-01-05 12:05 135阅读 0赞

使用guava的一致性哈希算法

<dependency>
              <groupId>com.google.guava</groupId>
              <artifactId>guava</artifactId>
              <version>23.0</version>
          </dependency>

然后自己写一个类，继承AbstractLoadBalancerRule：

package com.yy.item.controller;
    
    import com.google.common.hash.Hashing;
    import com.netflix.client.config.IClientConfig;
    import com.netflix.loadbalancer.AbstractLoadBalancerRule;
    import com.netflix.loadbalancer.ILoadBalancer;
    import com.netflix.loadbalancer.IRule;
    import com.netflix.loadbalancer.Server;
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    import org.springframework.web.context.request.RequestContextHolder;
    import org.springframework.web.context.request.ServletRequestAttributes;
    
    import javax.servlet.http.HttpServletRequest;
    import java.util.List;
    import java.util.Objects;
    
    public class ConsistentHashRule extends AbstractLoadBalancerRule implements IRule {
        private Logger log = LoggerFactory.getLogger(ConsistentHashRule.class);
    
        @Override
        public void initWithNiwsConfig(IClientConfig clientConfig) {
    
        }
    
        @Override
        public Server choose(Object key) {
            return choose(getLoadBalancer());
        }
    
        private Server choose(ILoadBalancer lb) {
            if (lb == null) {
                log.warn("no load balancer");
                return null;
            }
    
            Server server = null;
            int count = 0;
            while (count++ < 10) {
                List<Server> reachableServers = lb.getReachableServers();
                List<Server> allServers = lb.getAllServers();
                int upCount = reachableServers.size();
                int serverCount = allServers.size();
                if ((upCount == 0) || (serverCount == 0)) {
                    log.warn("No up servers available from load balancer: " + lb);
                    return null;
                }
                //获取请求URI
                HttpServletRequest request = ((ServletRequestAttributes) Objects.requireNonNull(RequestContextHolder.getRequestAttributes())).getRequest();
                String uri = request.getServletPath() + "?" + request.getQueryString();
    
                int hashcode = uri.hashCode();
                //一致性哈希，直接返回第几个数
                int model = Hashing.consistentHash(hashcode, serverCount);
    
                server = allServers.get(model);
    
                if (server == null) {
                    Thread.yield();
                    continue;
                }
    
                if (server.isAlive() && (server.isReadyToServe())) {
                    return (server);
                }
    
                server = null;
            }
    
            if (count >= 10) {
                log.warn("No available alive servers after 10 tries from load balancer: "
                        + lb);
            }
            return server;
    
    
        }
    }