cluster 简介 invoker Directory Router loadbalance Failover Failfast Failsafe Failback Forking 负载均衡算法：轮询(roundrobin)，最少活跃(leastActive) FsofProtocol 两个方法： export 暴露 幂等 refer 获取proxy invoker Cluster directory join Directory /** * Directory. (SPI, Prototype, ThreadSafe) * * <a href="http://en.wikipedia.org/wiki/Directory_service">Directory Service</a> * * @see com.alibaba.dubbo.rpc.cluster.Cluster#join(Directory) * @author william.liangf */ public interface Directory<T> extends Node { /** * get service type......