Configure Knox auto-discovery for large clusters

How to configure Knox’s service auto-discovery feature for large clusters.

By default, the auto-discovery feature of Cloudera Manager through Knox uses the API v32 endpoint:

GET /clusters/{clusterName}/services/{serviceName}/roles/{roleName}/config

This method fetches the role configuration parameters for each service role. This causes a large number of REST API calls in case of large clusters.

For large clusters, the following endpoint should be used instead:

GET /clusters/{clusterName}/services/{serviceName}/roles/configs

If the endpoint is available in your Cloudera Manager, follow these steps to configure the auto-discovery method in Knox:

From Cloudera Manager > Knox > Configuration, add a new entry in Knox Gateway Advanced Configuration Snippet (Safety Valve) for conf/gateway-site.xml, and insert these properties:
```
gateway.cloudera.manager.service.discovery.role.fetch.strategy=byService
gateway.cloudera.manager.service.discovery.api.version=v54
```
important
If you upgrade Cloudera Manager to 7.13.1 version, the endpoint is available using API v57. In this case, set the API version to v57.
Save the changes.
Refresh the Knox instances’ configuration: the Refresh needed stale configuration indicator appears; click it and wait until the refresh process completes.
Validate using the Knox homepage.
The default auto-discovery method can be reset by one of the following methods:
- Remove the properties from Knox Gateway Advanced Configuration Snippet (Safety Valve) for conf/gateway-site.xml
- Insert these properties into Knox Gateway Advanced Configuration Snippet (Safety Valve) for conf/gateway-site.xml:
```
gateway.cloudera.manager.service.discovery.role.fetch.strategy=byRole
gateway.cloudera.manager.service.discovery.api.version=v32
```