Puppet, Hiera - Some notes on Hiera

Puppet Class Parameters priority:
  1.. use value that was explicitly set
  2.. check hiera for ClassName::ParameterName
  3.. use default value in class def
  4.. fail compilation with error

Hiera lookups get a copy of ALL variables currently available to puppet.
Hiera can use these in "interpolation tokens"

Hiera lookup functions:
  hiera - priority lookup
  hiera_array - array merge lookup
  hiera_hash - odd


src:  https://docs.puppetlabs.com/hiera/1/puppet.html#hiera-lookup-functions