Manually Failing Over Your Cluster

If you are running a HDFS service with High Availability enabled, you can manually cause your Active NameNode to failover to your Standby NameNode. This is useful for planned downtime — for hardware changes, configuration changes, or software upgrades of your primary host.

To perform a manual failover:

  1. From the Services tab, select your HDFS service.
  2. Click the Instances tab.
  3. Click Manual Failover...
  4. From the pop-up, select the NameNode that should be made active, then click Manual Failover.
      Note: For advanced use only: You can set the Force Failover checkbox to force the selected NameNode to be active, irrespective of its state or the other NameNode's state. Forcing a failover will first attempt to failover the selected NameNode to active mode and the other NameNode to standby mode. It will do so even if the selected NameNode is in safe mode. If this fails, it will proceed to transition the selected NameNode to active mode. To avoid having two NameNodes be active, use this only if the other NameNode is either definitely stopped, or can be transitioned to standby mode by the first failover step.
  5. When all the steps have been completed, click Finish.

The Cloudera Manager will transition the NameNode you selected to be the Active NameNode, and the other NameNode to be the Standby NameNode. HDFS should never have two Active NameNodes.

  Note:

If you are using a NFS-mounted shared edits directory, a fencing method must be configured in order for failover (either automatic or manual) to function — Cloudera Manager configures this automatically. See Fencing Methods if you want more information about where this is set through Cloudera Manager.

For details of the fencing methods supplied with CDH4, and how fencing is configured, see the Fencing Configuration section in the CDH4 High Availability Guide.