5.3.7. NameNode process down alert

This alert is triggered if the NameNode process cannot be confirmed to be up and listening on the network for the configured critical threshold, given in seconds. It uses the Nagios check_tcp ^[1]plugin.

5.3.7.1. Potential causes

The NameNode process is down on the HDFS master host
The NameNode process is up and running but not listening on the correct network port (default 8201)
The Nagios server cannot connect to the HDFS master through the network.

5.3.7.2. Possible remedies

Check for any errors in the logs (/var/log/hadoop/hdfs/)and restart the NameNode host/process using the HMC Manage Services tab.
Run the netstat-tuplpn command to check if the NameNode process is bound to the correct network port
Use ping to check the network connection between the Nagios server and the NameNode

^[1]The check_tcp plugin tests if a process is up and listening on a specified socket (host/port) address. Ambari uses this check to determine the run time status of various Hadoop services. With future Ambari releases this functionality will include more robust tests such as running some service operations to make sure the service is healthy.

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