Supporting Rolling Patches

The rolling patch function indicates that patches are installed or uninstalled for one or more services in a cluster by performing a rolling service restart (restarting services or instances in batches), without interrupting the services or within a minimized service interruption interval. Services in a cluster are divided into the following three types based on whether they support rolling patch:

Services supporting rolling patch installation or uninstallation: All businesses or part of them (varying depending on different services) of the services are not interrupted during patch installation or uninstallation.
Services not supporting rolling patch installation or uninstallation: Businesses of the services are interrupted during patch installation or uninstallation.
Services with some roles supporting rolling patch installation or uninstallation: Some businesses of the services are not interrupted during patch installation or uninstallation.

Table 1 provides services and instances that support or do not support rolling restart in the MRS cluster.

**Table 1** Services and instances that support or do not support rolling restart
Service	Instance	Whether to Support Rolling Restart
HDFS	NameNode	Yes
	ZKFC
	JournalNode
	HttpFS
	DataNode
Yarn	ResourceManager	Yes
Yarn	NodeManager	Yes
Hive	MetaStore	Yes
	WebHCat
	HiveServer
MapReduce	JobHistoryServer	Yes
HBase	HMaster	Yes
	RegionServer
	ThriftServer
	RESTServer
Spark	JobHistory	Yes
	JDBCServer	Yes
	SparkResource	No
Hue	Hue	No
Tez	TezUI	No
Loader	Sqoop	No
ZooKeeper	QuorumPeer	Yes
Kafka	Broker	Yes
Kafka	MirrorMaker	No
Flume	Flume	Yes
Flume	MonitorServer	Yes
Storm	Nimbus	Yes
	UI
	Supervisor
	LogViewer

Installing a Patch

Log in to the MRS management console.
Choose Clusters > Active Clusters and click the name of the cluster to be queried to enter the page displaying the cluster's basic information.
On the Patch Information page, click Install in the Operation column.
On the Warning page, enable or disable Rolling Patch.

Figure 1 Rolling patch installation
- Enabling the rolling patch installation function: Services are not stopped before patch installation, and rolling service restart is performed after the patch installation. This minimizes the impact on cluster services but takes more time than common patch installation.
- Disabling the rolling patch uninstallation function: All services are stopped before patch uninstallation, and all services are restarted after the patch uninstallation. This temporarily interrupts the cluster and the services but takes less time than rolling patch uninstallation.
- The rolling patch installation function is not available in clusters with less than two Master nodes and three Core nodes.
Click OK to install the target patch.
View the patch installation progress.
1. Access MRS Manager. For details, see Accessing MRS Manager (MRS 2.x or Earlier).
2. Choose System > Manage Patch. On the Manage Patch page, you can view the patch installation progress.
For the isolated host nodes in the cluster, follow instructions in Restoring Patches for the Isolated Hosts to restore the patch.

Uninstalling a Patch

Log in to the MRS management console.
Choose Clusters > Active Clusters and click the name of the cluster to be queried to enter the page displaying the cluster's basic information.
On the Patch Information page, click Uninstall in the Operation column.
On the Warning page, enable or disable Rolling Patch.

Figure 2 Rolling patch uninstallation
- Enabling the rolling patch uninstallation function: Services are not stopped before patch uninstallation, and rolling service restart is performed after the patch uninstallation. This minimizes the impact on cluster services but takes more time than common patch uninstallation.
- Disabling the rolling patch uninstallation function: All services are stopped before patch uninstallation, and all services are restarted after the patch uninstallation. This temporarily interrupts the cluster and the services but takes less time than rolling patch uninstallation.
- The rolling patch uninstallation function is not available in clusters with less than two Master nodes and three Core nodes.
Click OK to uninstall the target patch.
View the patch uninstallation progress.
1. Access MRS Manager. For details, see Accessing MRS Manager (MRS 2.x or Earlier).
2. Choose System > Manage Patch. On the Manage Patch page, you can view the patch uninstallation progress.
For the isolated host nodes in the cluster, follow instructions in Restoring Patches for the Isolated Hosts to restore the patch.