# host.yaml
profile::mariadb::shard: s1

# manifest.pp
class profile::mariadb (
 $shard
) {
 # do something with $shard
 include mysql
}
class profile::mariadb::core_test {
  include profile::mariadb
  # if we also need shard here
  $shard = $profile::mariadb::shard 
  # or just use $profile::mariadb::shard  directly
 
}