Puppet users - May 2010 - variables in variable and class names

Hi, this may sound a bit strange, so let me tell you first what the
problem is that i try to solve and maybe there is already a better
solution.

Some background: We use 3 different environments on our puppetmaster and
we implemented something like a release management as a workflow for this.
Cause why should you invent something new when you can steal it from
software engineers ;-). The release management is a simple tag convention
in the version management and a post-receive script that makes a checkout
the newest version for each environment. We have a release cycle where we
tag a version for integration that worked without regression for a while
on the testing environment. For production exactly the same.

Now there are sometimes settings, config files or classes that only apply
on a single host and the whole release cycle makes no sense and you really
don''t want to wait some days until the new firewall rule apply on a
production system because there are already other changes in the pipe and
you can''t just "tag it trought".

So my plan is to have a special module that is always checked out from
HEAD in every environment and the classes there, if defined are only
applied on a singe host, never group of hosts. If they are not defined the
host is just uses the defaults. For files this is easy, but for variables
or classes i found no way so far to implement this.

Here is an NON working example that may describe what i want to do:

-----------------------------------------------------------
# Settings i want to overwrite only for "mynewserver".
# This class is only there if i need at least one special settings
class hostconfig::mynewserver::settings {
    $myvar = "overwritten for this host"
}

# Load the settings class if it exists
if defined( hostconfig::${hostname}::settings ) {
    include hostconfig::${hostname}::settings
}

# if we need a variable that can be overwritten i have to check
# if it exists. If it does not we use the default value.
if defined( $hostconfig::${hostname}::settings::myvar ) {
    $var = $hostconfig::${hostname}::settings::myvar
} else {
    $var = "default"
}

notice( $var )

------------------------------------------------------------------

If the host is a standard system i should i want to do absolutely nothing,
cause it gets its classes and settings from regex patterns in the default
node config based on the server name (We only have a hand full of
different servers but many of them).

Any ideas how i can implement this in a way that works?

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Does class hostconfig::mynewserver::settings contain just variables?

You could do something like this (from
http://groups.google.com/group/puppet-users/browse_thread/thread/5ba9d8b1ed4d4d1a/1214d616ef5caec0)...
==In my nodes.pp, I define certain "default" variables at the top of
the
manifest, outside of any node definitions.  If I want to override a
default variable, I redefine the variable inside of the specific node
definition, before I include the class that uses the variable.

For example:
> cat nodes.pp
# defaults
$dnsname = "foo.local"
$dnsserver = [ "192.168.1.1", "192.168.2.1" ]
$dnssearchpath = [ "foo", "foo.local" ]

node "standard.node" {
    include basenode
}

node "nonstandard.node" {
    $dnsname = "bar.local"
    $dnsserver = [ "192.168.100.1", "192.168.101.1" ]
    $dnssearchpath = [ "bar", "bar.local" ]
    include basenode
}

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