Puppet

Currently, I’m working on our new Nagios module, so my example is Nagios orientated, but I’m sure you can see the benefit for other resources too. Mainly I’d like to use it for “magic resource creation”. Take the example below, hostgroups aren’t very interesting and we never use any other option than giving them a name, so we can more easily search for them in the Nagios interface. Actually, I don’t even know if there are other options at all… I use the syntax I proposed in the ticket, just for clarity’s sake.

define monitor_host ($hostgroups = "", ... ) {
  ?@@nagios_hostgroup { $hostgroups:
    target => "/etc/nagios3/conf.d/hostgroups.cfg",
    tag => "monitor-local",
  }

  ?@@file { "/etc/nagios3/conf.d/hostgroups.cfg":
    owner => "nagios",
  }

  @@nagios_host { $name:
    hostgroups => $hostgroups,
    ...
  }
}

This can be done using ‘if ! defined’ when you only enter one hostgroup, but it’s impossible if you want to do this with multiple hostgroups.

The idea is that there’s a lot of automation you can do with puppet that requires the creation of ‘stock’ resources, which can be created if you only know their name. Allowing for this request, would make it easier to handle arrays for this.

Another way to solve it, is by creating loop controls for arrays in the puppet DSL. That might actually solve even more problems than just the resource creation for resources that might already be created. That way you could do something like:

if $hostgroups {
  for group in $hostgroups {
    if ! defined(Nagios_hostgroup[$group]) {
      @@nagios_hostgroup { $group:; }
    }
    etc.
  }
}

PS. I believe nagios_host’s hostgroups setting currently doesn’t allow arrays, but that’s easily fixed with an inline_template or if #2990 gets accepted.