If the admin attempts to shutdown the HDFS NameNode(s) through Ambari in following situations:
- HDFS service > Stop / Restart All components,
- HDFS summary/configs page> Restart Affected,
- Host Details > NameNode Stop / Restart,
- Host Details > Stop/Restart all components,
- Stop All Services
- Hosts Actions > All/Selected/Filtered Hosts > Hosts > Stop/Restart All Components
A check should be run to see when the last HDFS checkpoint was created.
If the checkpoint was created more than 12 hours ago, Ambari should prompt the user to save/create a checkpoint first.
"The last HDFS checkpoint is older than 12 hours. Make sure that you have taken a checkpoint before proceeding. Otherwise, the NameNode(s) can take a very long time to start up."
The check should be skipped if there's no NameNode to shut down (i.e., all NameNodes are already down) as a result of the operation.
The user should be warned with instructions to create a new checkpoint, it is up to User if they would like to create a new checkpoint. User can always proceed with button "Next".
The Active NameNode JMX is checked to figure out when the last checkpoint was taken. If the Active NameNode JMX is not available for whatever reason, check for any available NameNode JMX (Standby).
If no JMX info is available, then something is wrong. In this case, display warning along the line of "Could not determine the age of the last HDFS checkpoint. Please ensure that you have a recent checkpoint. Otherwise, the NameNode(s) can take a very long time to start up."
- NameNode shutdown that are part of any Wizard will not be taken care of in this RMP (e.g., NameNode HA wizard)