Data Hub uses cluster templates for defining cluster topology: defining host groups and components installed on each host group.
A cluster template is a reusable template in JSON format that can be used for creating multiple Data Hub clusters with identical Cloudera Runtime settings. It primarily defines the list of host groups and how components of various Cloudera Runtime services are distributed on these host groups. A cluster template allows you to specify stack, component layout, and configurations to materialize a cluster instance via Cloudera Manager REST API, without having to use the Cloudera Manager install wizard. After you provide the cluster template to Data Hub, the host groups in the JSON are mapped to a set of instances when starting the cluster, and the specified services and components are installed on the corresponding nodes.
Data Hub includes a few default cluster templates and allows you to upload your own cluster templates. Custom cluster templates can be uploaded and managed via the CDP web interface or CLI and then selected, when needed, for a specific cluster.