Assigns parameters to a node using an hash merge lookup that retrieves the values for a user-specified key from a Hiera data source.

To use hiera_param, the following configuration is required:

• A key name to use for parameters, e.g. params.
• A line in the puppet sites.pp file (e.g. /etc/puppet/manifests/sites.pp) reading hiera_param('params'). Note that this line must be outside any node definition and below any top-scope variables in use for Hiera lookups.
• Class keys in the appropriate data sources. In a data source keyed to a node's role, one might have:

---
params:
  dc: 'NYC'
  cluster: 'web'

In addition to the required key argument, hiera_param accepts two additional arguments:

• a default argument in the second position, providing an hash to be returned in the absence of matches to the key argument
• an override argument in the third position, providing a data source to consult for matching values, even if it would not ordinarily be part of the matched hierarchy. If Hiera doesn't find a matching key in the named override data source, it will continue to search through the rest of the hierarchy.