Adding a Role Instance

After creating services, you can add role instances to the services. For example, after initial installation in which you created the HDFS service, you can add a DataNode role instance to a host where one was not previously running. Upon upgrading a cluster to a new version of Cloudera Runtime you might want to create a role instance for a role added in the new version.

  1. Go to the service for which you want to add a role instance. For example, to add a DataNode role instance, go to the HDFS service.
  2. Click the Instances tab.
  3. Click the Add Role Instances button.
  4. Customize the assignment of role instances to hosts. The wizard evaluates the hardware configurations of the hosts to determine the best hosts for each role. The wizard assigns all worker roles to the same set of hosts to which the HDFS DataNode role is assigned. You can reassign role instances.

    Click a field below a role to display a dialog box containing a list of hosts. If you click a field containing multiple hosts, you can also select All Hosts to assign the role to all hosts, or Custom to display the hosts dialog box.

    The following shortcuts for specifying hostname patterns are supported:
    • Range of hostnames (without the domain portion)
      Range Definition Matching Hosts
      10.1.1.[1-4] 10.1.1.1, 10.1.1.2, 10.1.1.3, 10.1.1.4
      host[1-3].company.com host1.company.com, host2.company.com, host3.company.com
      host[07-10].company.com host07.company.com, host08.company.com, host09.company.com, host10.company.com
    • IP addresses
    • Rack name

    Click the View By Host button for an overview of the role assignment by hostname ranges.

  5. Click Continue.
  6. In the Review Changes page, review the configuration changes to be applied.
    Confirm the settings entered for file system paths. The file paths required vary based on the services to be installed. For example, you might confirm the NameNode Data Directory and the DataNode Data Directory for HDFS.
  7. Click Continue.
The wizard finishes by performing any actions necessary to prepare the cluster for the new role instances. For example, new DataNodes are added to the NameNode dfs_hosts_allow.txt file. The new role instance is configured with the default role group for its role type, even if there are multiple role groups for the role type. If you want to use a different role group, follow the instructions in the topic Managing Role Groups for moving role instances to a different role group