While adding nodes in existing clusters using Cloudbreak UI , I am getting below error..
:54:43 Cluster upscale failed.: The node count '2' for hostgroup 'host_group_master_2' cannot be less than '1' or more than '1' because of 'HIVE_SERVER' component
whats could be reason behind this?
I assume you'd like to upscale a worker hostgroup - not a hostgroup which contains master components (like HIVE_SERVER) in 'host_group_master_2'. Master hostgroups can't be upscaled - if you'd like to do HA (for components which support that) than it's a different story. Bottom line - you can upscale worker hostgroups, not master ones (as it does not make too much sense upscale master hostgroups anyway).
In general if you check the default blueprints in Cloudbreak you will see that none of the Master hostgroups are doing any work in case you submit a job/query.etc - they only run master/server and UI components. All the work is done by the slave/worker hostgroups - where you have the datanodes or for example HBase region servers.
This is because you're trying to upscale a host group which contains master services. At the moment it is not allowed since you'll need to configure those services for HA. This is not supported yet during upscale.