Puppet manifest example

Inside templates you have access to a scope object. All of the functions that you can access in the puppet manifests can be accessed via that scope object, although not via the same name. Prepend "function_" to the beginning of the function name. For example, here I included one template inside another: <%= scope.function_template("template2.erb") %>

http://reductivelabs.com/trac/puppet/wiki/PuppetTemplating has great documentation about the scope object inside templates. For really deep information about template and functions you can look inside lib/puppet/parser/templatewrapper.rb and lib/puppet/parser/functions.rb.

Hiera is included in Puppet 3.0 - in 2.7, you'll need to install it separately on your masters.

Since it sounds like you'll want the mapping to be global, you'll want to put it in a Hiera file that applies to all systems. So in your hiera.yaml, you'll want something like..

:backends:
  - yaml

:hierarchy:
  - common

:yaml:
   :datadir: /etc/puppet/hieradata

Then in /etc/puppet/hieradata/common.yaml, set up your port mappings:

port_app_1: "27960"
port_app_2: "27961"

With that in place, you can look it up in your vhost config.

$vhost_port = hiera("port_${name}")