There is an increasing demand for clusters with some of the components being managed externally to Ambari.
This ticket addresses the problem where the cluster contains a HDFS_CLIENT but server HDFS server components are external and NAMENODE is HA.
In this cases, cluster template validation failed as there were 0 name nodes which is less than the expected minimum of two.
Going forward the following setup should pass validation:
- Namenode HA is enabled
- There are 0 namenodes
- all namenode dfs rpc addresses point to an external fqdn.
This will give sufficent protection against accidentally omitted namenodes, however will enable clusters with external namenodes.