master_domain?  Is this meant to be the NameNode host?  Maybe you want to do:

```$namenode_host = $::cdh4::hadoop::primary_namenode_host```

That way this will have a valid default value.  Actually, this probably shouldn't even be a configurable parameter on cdh4::hbase class.  You should just set the variable to this value manually in the ```cdh4::hbase``` class.