Managing MRS Role Instance Groups
In a large-scale MRS cluster, multiple instances of the same role (such as DataNode or NodeManager) may be distributed across nodes with different hardware configurations. Administrators must apply different configuration parameters (such as memory and CPU limits) to instance groups with different hardware configurations. Modifying configurations instance by instance is inefficient and error-prone. How can you efficiently manage the instance configurations of the same role in batches? To solve this, MRS provides the role instance group feature, which allows you to group and manage instances of the same role based on hardware specifications or custom criteria. Modifying the configuration parameters of an instance group automatically applies the changes to all instances in that group, significantly improving O&M efficiency.
Notes and Constraints
- This section applies to MRS 3.x or later.
- Each instance must belong to only one instance group. When an instance is installed for the first time, it belongs to the default instance group named Role name-DEFAULT by default. This default instance group cannot be modified or deleted.
Creating and Managing MRS Role Instance Groups
- Log in to FusionInsight Manager of the MRS cluster.
For details about how to log in to FusionInsight Manager, see Accessing MRS Manager.
- On MRS Manager, choose Cluster > Services.
- Click the specified service name on the service management page.
- On the displayed page, click Instance Groups.
Click
and configure parameters as prompted.Figure 1 Creating an instance group
Table 1 Instance group configuration parameters Parameter
Description
Group Name
Instance group name. The name can contain only letters, digits, underscores (_), hyphens (-), and spaces. It must start with a letter, digit, underscore (_), or hyphen (-), cannot end with a space, and can contain a maximum of 99 characters.
Role
Role type contained in the instance group, such as DataNode or NodeManager. The role cannot be changed after the instance group is created.
Copy From
(Optional) Source instance group from which configuration values are copied to the new group. If this parameter is left empty, system default values are used for the new group. Set this parameter if you want to quickly create an instance group based on the configurations of an existing one.
Description
(Optional) Description of the instance group. The description can contain up to 200 characters, including letters, digits, commas (,), periods (.), underscores (_), spaces, and newlines.
- Click OK.
- You can perform the following operations on an instance group as needed.
- Modifying an instance group: On the Instance Group page, locate the target instance group, click
, and modify parameters as prompted. The default instance group cannot be modified. - Deleting an instance group: Click Instance Groups. On the Instance Groups page, locate the row that contains the target instance group. Click
. In the displayed dialog box, click OK. The default instance group cannot be deleted. You can delete unnecessary or unused instance groups. Before deleting an instance group, migrate all instances in the group to other instance groups. The default instance group cannot be deleted.
- Viewing instance group information: On the Instance Groups page, select a role. On the Basic page, view all instances of the instance group.
To move an instance from an instance group to another, perform the following operations:
- Select the instance to be moved and click Move.
- In the displayed dialog box, select the instance group to which the instance will be moved.
During migration, the configuration of the target instance group is automatically inherited. If the instance configuration is modified before migration, the modified instance configuration will be applied.
- Click OK.
Restart any service or instance with expired configurations to make the new settings take effect.
- Configuring instance group parameters: On the Instance Groups page, select a role in the navigation pane, click Configuration, adjust the configuration parameters, and click Save. The configuration will take effect on all instances in the instance group.
- Modifying an instance group: On the Instance Group page, locate the target instance group, click
FAQs
Q: How do I add an existing instance to a new instance group?
A: On the Instance Groups tab, select the target role in the navigation pane, select the instances you want to move, and click Move. Then, in the displayed dialog box, select the target instance group and click OK to complete the move. After the move, restart any instance whose configuration has expired to apply the changes.
Q: What should I do if an instance group cannot be deleted because it contains undeleted instances?
A: Before deleting an instance group, you must move all of its instances to another group. On the Basic tab, select the instances and move them to the target instance group. Once the group is empty, you can delete it. Note that you cannot delete the default instance group named Role name-DEFAULT.
Q: What should I do if a configuration does not take effect after I move an instance to a new group?
A: On the Basic tab, check the configuration status of the instance. If the configuration has expired, restart the instance. Check whether the configuration parameters for the new instance group are correct. If the instance configuration was modified before migration, instance-level settings take precedence. Determine whether to clear the instance-level configuration so the instance fully inherits the group-level configuration.
Helpful Links
- For details about basic management operations of an MRS cluster, see Managing an MRS Cluster.
- For details about how to modify configuration parameters for a single instance, see Modifying the Configuration Parameters of an MRS Cluster Component.
- For details about basic concepts of MRS roles and instances, see MRS Cluster Overview.
