org.apache.catalina.cluster 包
该包包含集群相关的代码(Cluster)，集群的基类是实现了org.apache.catalina.Cluster并实现了集群协议的类。 仅有的集群协议是基于JGCluster.java 类的JavaGroups。
| CatalinaCluster |
A CatalinaCluster interface allows to plug in and out the different cluster implementations 该接口允许嵌入或嵌出不同的不同的集群实现 |
| ClusterDeployer | 无内容 |
| ClusterManager |
The common interface used by all cluster manager. 所有集群管理器的常用接口 |
| ClusterMessage | 无内容 |
| ClusterReceiver |
Cluster Receiver Interface 集群接收器接口 |
| ClusterSender | 无内容 |
| ClusterSession | 无内容 |
| ClusterValve |
Cluster Valve Interface to mark all Cluster Valves Only those Valve can'be configured as Cluster Valves （这个doc写的真差，读者自个琢磨吧，我没有琢磨明白） |
| Member |
The Member interface, defines a member in the Cluster. 定义了集群中的成员 |
| MembershipListener |
The MembershipListener interface is used as a callback to the membership service. 该接口用于成员服务的回调 |
| MembershipService |
The membership service helps the cluster determine the membership logic in the cluster. 用于帮助集群确定成员的逻辑关系 |
| MessageListener | 无内容 |