【HDFS】ActiveNamenodeResolver#getNamespaces 方法调用点梳理
获取所有的注册在router里的active状态的集群。/***Getalistofallnamespacesthatareregisteredandactiveinthe*federation.**@returnListofnamespacesinthefederation*@throwsIOExceptionThrowsexceptionifthenamespacelistisnot*avai