Using Hiera to set global variables

I was able to find following solution using create_resource function

class hosts ($hosts = hiera_hash("hosts"))  {
  create_resources( 'host', $hosts )
}

it needs slight modification to my original data (change hash key to ip to match resource parameter):

---- 
hosts: 
  host1.example.com: 
    ip: 10.0.0.1 
    host_aliases: host1 
 host2.example.com: 
    ip: 10.0.0.2 
    host_aliases: host2 

I've done it this way. It might be a bit cleaner to use an ENC or Hiera to do a lookup based on the server name or role and decide whether to include ntp::server or whatnot, but this is fairly simple and requires no additional software or setup.

Keep in mind that Puppet's inheritance model isn't normal. You will have trouble unless your use of it is very very simple. I would not inherit more than once in any module.

class ntp {
  include ntp::install, ntp::config, ntp::sevice
  Class['ntp::install'] -> Class['ntp::config'] ~> Class['ntp::service']
}

class ntp::config {
  file { 'ntp.conf':
    ensure  => present,
    content => template('ntp/ntp.erb'),
  }
}

class ntp::config::server inherits ntp::config {
  File['ntp.conf'] { content => template('ntp/ntp.conf.server.erb'), }
}

node basenode {
  include ntp
}
node /^ntp\d+/ inherits basenode {
  include ntp::config::server
}