执行“hdfs dfs -ls /”出现“Operation category READ is not supported in state standby”报错解决

问题：

17/07/05 17:15:28 INFO retry.RetryInvocationHandler: Exception while invoking getFileInfo of class ClientNamenodeProtocolTranslatorPB over vm1/192.168.137.121:9000 after 5 fail over attempts. Trying to fail over after sleeping for 19260ms.
java.net.ConnectException: Call From vm1/192.168.137.121 to vm1:9000 failed on connection exception: java.net.ConnectException: Connection refused; For more details see:  http://wiki.apache.org/hadoop/ConnectionRefused

解读

查看报错信息中，有一个“ConnectionRefused”，初步认为节点之间连接问题。

然后 jps 查看一下，发现 namenode居然没有跟着启动。

症结

报错中 vm1 namenode没有启动。

解决

hdfs haadmin -getServiceState vm1