Hiera provides an interesting function called
hiera_include, which allows you to include all the classes defined for a given key.
This, in practice, exploits the Hiera flexibility to provide classes to nodes as does an External Node Classifier.
It's enough to place in our
/etc/puppet/manifests/site.pp a line like this:
Then, define in our data sources a
classes key with an array of the classes to include.
In a YAML-based backend, it would look like the following:
--- classes: - apache - mysql - php
This is exactly the same as having something like the following in our
include apache include mysql include php
classes key (it can have any name, but
classes is a standard de facto) contains an array, ...