Name Node services fail over

[#1]

I need to know if there was any failover happened on name node services. Where can I get this information.

Is there any REST API ?

[#2]

@Kumar Veerappan

The Following kind of Ambari API call can show which NameNode is Active and which one is StandBy.

Syntax:

curl -iv -u admin:admin -H "X-Requested-By: ambari" -X GET  "http://$AMBARI_HOST:8080/api/v1/clusters/$CLUSTER_NAME/components/NAMENODE?ServiceComponentInfo/category=MASTER&fields=ServiceComponentInfo/service_name,host_components/metrics/dfs/FSNamesystem/HAState"

Example:

curl -iv -u admin:admin -H "X-Requested-By: ambari" -X GET  "http://amb25101.example.com:8080/api/v1/clusters/plain_ambari/components/NAMENODE?ServiceComponentInfo/category=MASTER&fields=ServiceComponentInfo/service_name,host_components/metrics/dfs/FSNamesystem/HAState"

.

Example Output of the above call might look like:

{
  "href" : "http://amb25101.example.com:8080/api/v1/clusters/plain_ambari/components/NAMENODE?ServiceComponentInfo/category=MASTER&fields=ServiceComponentInfo/service_name,host_components/metrics/dfs/FSNamesystem/HAState",
  "ServiceComponentInfo" : {
    "category" : "MASTER",
    "cluster_name" : "plain_ambari",
    "component_name" : "NAMENODE",
    "service_name" : "HDFS"
  },
  "host_components" : [
    {
      "href" : "http://amb25101.example.com:8080/api/v1/clusters/plain_ambari/hosts/amb25101.example.com/host_components/NAMENODE",
      "HostRoles" : {
        "cluster_name" : "plain_ambari",
        "component_name" : "NAMENODE",
        "host_name" : "amb25101.example.com"
      },
      "metrics" : {
        "dfs" : {
          "FSNamesystem" : {
            "HAState" : "active"
          }
        }
      }
    },
    {
      "href" : "http://amb25101.example.com:8080/api/v1/clusters/plain_ambari/hosts/amb25102.example.com/host_components/NAMENODE",
      "HostRoles" : {
        "cluster_name" : "plain_ambari",
        "component_name" : "NAMENODE",
        "host_name" : "amb25102.example.com"
      },
      "metrics" : {
        "dfs" : {
          "FSNamesystem" : {
            "HAState" : "standby"
          }
        }
      }
    }
  ]
* Connection #0 to host amb25101.example.com left intact
}

.

[#3]

@Kumar Veerappan

You will have to create an watcher/alert scripts that identifies which NN is active and alert/email if NN flips.

Namenode service provides JMX which has information on which NameNode is active. Your watcher script can query this data to identify if NN failovers.

name" : "Hadoop:service=NameNode,name=NameNodeStatus",
    "modelerType" : "org.apache.hadoop.hdfs.server.namenode.NameNode",
    "State" : "active",
    "NNRole" : "NameNode",
    "HostAndPort" : "host1:8020