If you are aware of the hadoop cluster namenodes, then you can try pinging them or send a curl request like below
curl 'http://my-namenode-lv-101:50070/jmx?qry=Hadoop:service=NameNode,name=NameNodeStatus'
{
"beans" : [ {
"name" : "Hadoop:service=NameNode,name=NameNodeStatus",
"modelerType" : "org.apache.hadoop.hdfs.server.namenode.NameNode",
"SecurityEnabled" : false,
"NNRole" : "NameNode",
"HostAndPort" : "my-namenode-lv-101:8020",
"LastHATransitionTime" : 1561605051455,
"State" : "standby"
} ]
}
If the state is Standby, then that is the current inactive node, you have to try the other nodes to find for which the State says 'active' ... example below:
curl 'http://my-namenode-lv-102:50070/jmx?qry=Hadoop:service=NameNode,name=NameNodeStatus'
{
"beans" : [ {
"name" : "Hadoop:service=NameNode,name=NameNodeStatus",
"modelerType" : "org.apache.hadoop.hdfs.server.namenode.NameNode",
"State" : "active",
"SecurityEnabled" : false,
"NNRole" : "NameNode",
"HostAndPort" : "my-namenode-lv-102:8020",
"LastHATransitionTime" : 1561605054944
} ]
}