Add custom variables to subscriptions

[bodgit]

This PR adds the ability to define custom variables with subscriptions. The use case for this is when I'm using sensu::subscription's in my various modules to subscribe to classes of checks that are scheduled on the server, but the server might not necessarily be pointing to the same resources as the client and so I'd like to make use of Sensu's :::parameter.name::: syntax. Trying to set all of the module-specific variables in my one class that installs the base Sensu client becomes messy and polluted with variables that don't belong there so it's tidier if they can be defined with the subscription that will ultimately use them.

I copied the code in the other types and also added some tests, (the sensu_subscription_spec.rb was empty previously so I just based them off the other definition tests).

[jamtur01]

@jlambert121 Any thoughts?

[bodgit]

Bueller?

[jamtur01]

@bodgit Waiting for some input from @jlambert121 although @rodjek might also have views.

[jlambert121]

Sorry for the delay. After a year of writing javascript my ruby is getting rusty. I like the concept of what this is doing by utilizing the sensu variables. Are you not able to put the variable you're looking for in the command parameter in puppet?

[bodgit]

Putting the variables directly into Puppet doesn't really help. Assume the following horribly contrived classes on a Sensu client that happens to be a RabbitMQ broker:

class mysensu {
  class { '::sensu':
    client => true,
  }

  ensure_packages(['nagios-plugin-http', 'nagios-plugin-...'])

  ...
}

class myrabbitmq (
  my_default_user,
  my_default_pass,
) {
  class { '::rabbitmq':
    default_user => $my_default_user,
    default_pass => $my_default_pass,
  }

  ::sensu::subscription { 'rabbitmq':
    custom => {
      rabbitmq => {
        check_user => $my_default_user,
        check_pass => $my_default_pass,
      },
    },
  }
}

Then on my Sensu server I have the following check defined:

::sensu::check { 'rabbitmq':
  command => 'check_http -I 127.0.0.1 -u /api/aliveness-test/%2f -p 15672 -a ":::rabbitmq.check_user:::":":::rabbitmq.check_pass:::"',
  subscribers => [
    'rabbitmq',
  ],
  ...
}

I can build multiple RabbitMQ servers each with different credentials and the Sensu server doesn't need to know what they are, nor do I need to define multiple checks with the credentials hardcoded for each permutation.

While I could add the custom parameters in the main sensu client class, it doesn't make sense to pollute it with RabbitMQ-specific parameters.

Does that help explain things?

[jamtur01]

Thanks!