Hiera default data in puppet modules

hiera.yaml

:hierarchy:
  - Nodes/%{fqdn}
  - common

:backends:
  - yaml
  - puppet

:yaml:
  :datadir: '/etc/puppet/hieradata'

:puppet:
  :datasource: data

mysql::server::package.pp

class mysql::server::package
{
  $package_name = hiera('mysql_server_package')

  package { $package_name:
    ensure => installed,
  }
}

mysqlmanifestsdata.pp

class mysql::data {
    case $::operatingsystem
    {
        ubuntu, debian: {
            $mysql_server_package  = 'mysql-server'
            $mysql_client_package  = 'mysql'
            $mysql_service         = 'mysqld'
        }
        centos, redhat: {
            $mysql_server_package  = 'mysql-server'
            $mysql_client_package  = 'mysql'
            $mysql_service         = 'mysqld'
        }
        default:
        {
            fail("Unknown OS: $::operatingsystem")
        }
    }
}