org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.ipc.StandbyException): Operation category READ is not supported in state standby
org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.ipc.StandbyException): Operation category READ is not supported in state standby 此问题，原来从web 页面查看，是两个节点都变成了standy，所以要切换
hdfs haadmin -transitionToActive --forcemanual nn1
再次访问就变一active，一个standy