Querying Hiera

In Puppet manifests, you can use the lookup() function to query Hiera for the specified key (you can think of Hiera as a key-value database, where the keys are strings, and values can be any type).

In general, you can use a call to lookup() anywhere in your Puppet manifests you might otherwise use a literal value. The following code shows some examples of this (lookup2.pp):

notice("Apache is set to use ${lookup('apache_worker_factor', Integer)} workers")

unless lookup('apparmor_enabled', Boolean) {
  exec { 'apt-get -y remove apparmor': }
}

notice('dns_allow_query enabled: ', lookup('dns_allow_query', Boolean))

To apply this manifest in the example environment, run the following command:

sudo puppet apply --environment pbg /examples/lookup2.pp
Notice: Scope(Class[main]): Apache is set to use 100 workers
Notice: Scope(Class[main]): dns_allow_query enabled:  true

Typed lookups

As we've seen, lookup() takes a second parameter which specifies the expected type of the value to be...