Puppet: How does hierarchy work if a role is matched?

Question

I'm trying to understand how does Puppet hierarchy works.

My Puppet server's hiera.yaml looks like so:

[root@puppet puppet]# cat hiera.yaml 
:backends: 
  - yaml 
:yaml: 
  :datadir: '/etc/puppet/hieradata/%{::environment}' 
:hierarchy: 
  - fqdns/%{::fqdn} 
  - roles/%{::role} 
  - domains/%{::domain} 
  - common

There are modules which I want all servers to have so I've put them in the common.yaml file and there are role-specific modules which are included in each role.yaml file.

When a server which matches a role in Puppet starts, the modules from the role.yaml file are loaded first. My question is: Once a server is matched with a role... will it stop there? or will it continue in the hierarchy and load the modules under the common.yaml as well?

If not, How can I make sure that this is how it will behave?

Edit #1: Here's an example of one of the role.yaml files:

[root@puppet roles]# cat dataorigin.yaml 
classes:
  - workspace

jdk_enable: true
jdk_ver: 1.6.0_41
component_ver: 1-1-5-17
tomcat_enable: true
debug_mode: true

fstab_params:
  mount1:
    mnt_src:  "isilonnj01.eyedcny.local:/ifs/Peer39/do_share"
    mnt_dest: "/doshare"
    mnt_opts: "tcp,hard,intr,noatime"
    mnt_dest_parent: ""

And the server's site.pp looks like so:

hiera_include("classes", [])
Package {  allow_virtual => false, }
node default {
include stdlib
}

Edit #2: Here's an example of a motd module:

include stdlib
class motd {
    file { "/etc/custom_motd.sh":
    path    => '/etc/custom_motd.sh',
    ensure  => present,
    owner   => "root",
    group   => "root",
    mode    => "775",
    content => template('motd/custom_motd.sh.erb'),
    #require => Class['nagios_client'],
    }

    file_line { 'enable motd':
    ensure  => present,
    line    => '/etc/custom_motd.sh',
    path    => '/etc/profile',
    require  => File['/etc/custom_motd.sh']
    }
}

The motd module is configured in the common.yaml file, and in the role.yaml file there's a module called workspace. How can I tell Puppet to load the motd module from the common.yaml file?

Answer 1

Hiera is a tool to lookup data. You give it a key name and it walks through its data files and returns the first match (which should be the most specific one) it comes up with, traversing downwards in its hierarchy.

Using it within puppet, you have more options what to do if there is more than one value for a key:

hiera
    Standard priority lookup. Gets the most specific value for a given key. 
    This can retrieve values of any data type (strings, arrays, hashes) 
    from Hiera.
hiera_array
    Uses an array merge lookup. Gets all of the string or array values 
    in the hierarchy for a given key, then flattens them into a single 
    array of unique values.
hiera_hash
    Uses a hash merge lookup. Expects every value in the hierarchy for
    a given key to be a hash, and merges the top-level keys in each 
    hash into a single hash. Note that this does not do a deep-merge 
    in the case of nested structures.

Using hiera as an ENC to load modules works like this (Emphasis added):

Note that the hiera_include function uses an array merge lookup to retrieve the classes array; this means every node will get every class from its hierarchy.

So if you followed the docs and used hiera_include, all classes you specified throughout the hierarchy for a node will be loaded.

In your example, assuming role=dataorigin, and that common.yaml looks like this:

---
classes:
 - a

Your site.pp will cause the modules workspace, stdlib and a to be assigned to the querying node.