Perform Express Upgrade

Ambari will check that your cluster meets the Prerequisites. A dialog will be presented with the results:

If any prerequisites are not met but are required, the result will be shown with an error. You will not be allowed to proceed with the upgrade. Make the appropriate corrections and return to Perform Upgrade again.
If any prerequisites are not met but are optional, the result will be shown with a warning. You will be allowed to Proceed with the upgrade.
A list of configuration changes (if any) will be displayed.

Once the prerequisite checks are complete, the upgrade will start. The time it takes to perform the upgrade dependents on many factors. As part of the Express upgrade process, each component in the cluster is restarted in parallel across all hosts, usually requiring less time than the serial approach used in the Rolling Upgrade.

The upgrade process involves a set of stages. This table lists the high-level stages and if the process requires any action by you during normal operation.

	Note
	If any stage fails, the upgrade will halt and prompt for action.

Stage	Description	Action Required
Stop Components for High-Level Services	This will stop all components for High-Level Services. This includes all master components except those of HDFS, HBase, ZooKeeper and Ranger.	None
Perform Backups	This is a confirmation step used to confirm that you have taken proper backups before proceeding.	You must acknowledge the prompt for database backups.
Stop Components for Core Service	Stops all components with HDFS, HBase, ZooKeeper and Ranger.	None
Update Target Stack	Updates the stack version in Ambari to the target version.	None
Update Service Configs	Updates (i.e. transfers or replaces) any configurations that are necessary for the upgrade.	None
Restart Components	Restarts all core components such as ZooKeeper, Ranger, HDFS, YARN, MapReduce2 and various Clients (Tez, Pig, Sqoop).	None
All Service Checks	All Service Checks are performed against the cluster.	If any service check fails, you will be prompted to Ignore and Continue, Downgrade or Retry. If you selected the “Skip all Service Check failures” option, you will only be prompted at the completion of all of the Service Checks.
Restart Components	Restarts the remaining components such as Oozie, Falcon, Hive, Spark and others.	None
Set Version on All Hosts	Sets the HDP version on all hosts to the target HDP version.	None
Finalize Upgrade Pre-Check	Checks if any hosts were not upgraded, either because the host was in Maintenance Mode, or one or more components on the host failed to upgrade (and were skipped).	Click on the list that displays "# hosts" for details on the hosts (and their components) that are not upgraded. You can Pause Upgrade, delete the hosts and return to finalize.
Finalize Upgrade	The component upgrades are complete. You are presented the option to Finalize, which when selected, completes the upgrade process + saves the cluster state.	Prompted to Finalize or Finalize Later or Downgrade.

Once the upgrade is complete, you have an option to Finalize the upgrade, to Finalize Later or to Downgrade. Finalizing later gives you a chance to perform more validation on the cluster. Downgrade moves the cluster version back to the previous version (basically: the reverse of the upgrade process stages). Once finalized, you cannot downgrade back to the previous version.

	Note
	If you choose to finalize later, both versions will be listed on the Stack and Versions tab with the starting version displaying as Current. It is not until you finalize that Ambari makes the target version the current version. Also, until you finalize, you will not be able to perform operational changes to the cluster (such as move components, change configurations, etc).

Click Finalize and the upgrade process is complete.

	Important
	An Express Upgrade from HDP 2.1 -> 2.3 has no option to "Downgrade" since the bits for HDP 2.1 will have to be removed midway through the process.

​Perform Express Upgrade