Installing a Rolling Patch

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.

In MRS 3.x, you cannot perform operations in this section on the management console.

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	Support Rolling Restart
Alluxio	AlluxioJobMaster	Yes
Alluxio	AlluxioMaster	Yes
ClickHouse	ClickHouseServer	Yes
ClickHouse	ClickHouseBalancer	Yes
CDL	CDLConnector	Yes
CDL	CDLService	Yes
Flink	FlinkResource	No
Flink	FlinkServer	No
Flume	Flume	Yes
Flume	MonitorServer	Yes
Guardian	TokenServer	Yes
HBase	HMaster	Yes
	RegionServer
	ThriftServer
	RESTServer
HetuEngine	HSBroker	Yes
	HSConsole
	HSFabric
	QAS
HDFS	NameNode	Yes
	Zkfc
	JournalNode
	HttpFS
	DataNode
Hive	MetaStore	Yes
	WebHCat
	HiveServer
Hue	Hue	No
Impala	Impalad	No
	StateStore
	Catalog
IoTDB	IoTDBServer	Yes
Kafka	Broker	Yes
Kafka	KafkaUI	No
Kudu	KuduTserver	Yes
Kudu	KuduMaster	Yes
Loader	Sqoop	No
MapReduce	JobHistoryServer	Yes
Oozie	oozie	No
Presto	Coordinator	Yes
Presto	Worker	Yes
Ranger	RangerAdmin	Yes
	UserSync
	TagSync
Spark	JobHistory	Yes
	JDBCServer
	SparkResource
Storm	Nimbus	Yes
	UI
	Supervisor
	Logviewer
Tez	TezUI	No
Yarn	ResourceManager	Yes
Yarn	NodeManager	Yes
Zookeeper	Quorumpeer	Yes

Installing a Rolling Patch

Log in to the MRS console.
On the Active Clusters page displayed by default, click the name of the target cluster to enter the cluster details page.
On the Patches 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 Yes 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 Rolling Patch

Log in to the MRS console.
On the Active Clusters page displayed by default, click the name of the target cluster to enter the cluster details page.
On the Patches 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.
- Only patches that are installed in rolling mode can be uninstalled in the same mode.
Click Yes 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.