On Friday, August 29, 2014 5:05:01 PM UTC-5, Mike Reed wrote:
>
> Hello all,
>
> To start, I would like to thank you in advance for your responses.
>
> I'm attempting to create a custom fact that will determine the network
> location of a node, based on it's hostname. Ideally this would be run on a
> node prior to the rest of the puppet modules because I will use the result
> as a top scope variable to assign certain values to nodes, based on their
> network location. My node hostnames currently subscribe to this convention:
>
> network-hostname/role-number (ie. home-elastic-01/work-mysql-02)
>
I would like to suggest that you *not* do this via a fact. More generally,
I consider it a principle of a good design to avoid creating any fact that
is strictly derivative of other facts.
You can get a top scope variable with the same value in several other ways,
principal among them:
1. Compute it directly at top scope in your site manifest
2. Compute it in a class that manages no resources, 'include' that class
at top scope, and set the top-scope variable from the class variable
As a subset of (1), you could consider creating and using a custom
function, which would be very clean as far as your manifests go.
Note, however, that for *most* purposes you don't actually need a top-scope
variable; you could instead use a class variable directly. Either way, you
should be using a fully-qualified name everywhere you refer to the variable
in your manifests, so the choice of namespace is mostly a personal
preference in that context. The only use I can think of where you actually
need a top-scope variable is if you want to interpolate it into Hiera
hierarchy definitions (which is indeed a perfectly reasonable thing to do).
Option 2 might look like this:
modules/site/manifests/hostname_info.pp:
----
class site::hostname_info {
$hostname_parts = split($::hostname, '-')
$network = $hostname_parts[0]
$role = $hostname_parts[1]
$number = $hostname_parts[2]
}
manifests/site.pp (or any other manifest where you need the info):
----
# ...
include 'site::hostname_info'
$host_network = $site::hostname_info::network
# ...
John
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