[Thincrust-devel] Re: RFC: Customizing an appliance install

[Brenton Leanhardt]

+++ Bryan Kearney [29/09/08 10:40 -0400]:
> Brenton Leanhardt wrote:
>> +++ Bryan Kearney [29/09/08 09:06 -0400]:
>>> Brenton Leanhardt wrote:
>>>> +++ Bryan Kearney [26/09/08 15:06 -0400]:
>>>>> I am looking for feedback on how to customize an appliance install. As 
>>>>> you may be aware, the appliance configuration engine uses puppet as 
>>>>> it's configuration syntax. The rational is that this is an up and 
>>>>> coming standard syntax, and should be familiar to those who do sysadmin 
>>>>> type work (Said another way, we don't need yet another DSL).
>>>>>
>>>>> The trick is how to allow a user (either via the gui or the command 
>>>>> line) to customize an appliance recipe. In puppet I have seen 2 ways to 
>>>>> push in custom information:
>>>>>
>>>>> 1) External Nodes
>>>>> 2) Facter
>>>>>
>>>>> I am thinking of using the latter, and would like to outline my 
>>>>> thoughts. Please feel free to offer up alternative solutions.
>>>>>
>>>>> Goal:
>>>>>
>>>>> Create recipes which can externalize a small set of data which the user 
>>>>> needs to provide in order to the appliance to be configured.
>>>>>
>>>>> Implementation
>>>>>
>>>>> A module, or a recipe can deliver one or more "external facts". They 
>>>>> will be delivered in the form:
>>>>>
>>>>> name:default_value:query_text
>>>>
>>>> This seems good to me.  In fact similar to how Genome's "machine type"
>>>> DSL generates parameters for external nodes.  One thing I've thought
>>>> about, that I think could be a better approach, is storing this sort
>>>> of information in a special syntax (probably embedded in comments
>>>> JavaDoc style) so that this information would ship with the module as
>>>> opposed to keeping it in a separate file.
>>>
>>> Yeah.. I think this is a good way to go. Keeping the number of files to a 
>>> minimum would be good. Do you have a syntax chart for the genome DSL?
>>
>> I've attached a sample config file.  You can see the code here:
>> http://git.fedorahosted.org/git/genome.git?p=genome.git;a=tree;f=tools/genome-dsl;h=63b152ed2fca87bf47ebcae873c6ffe56fa87d96;hb=HEAD
>
>
> What do you think of this. Following the rdoc convention
>
> # :default_value Foo
> # :prompt What should the value of Foo be?
> $variable = value_from_user()
>
> This would result in a custom function which is executed at runtime to pull 
> in the value (not polluting facter) and would feel somewhat rubyish.
>
> -- bk
>

Did I say JavaDoc? I meant rdoc. :)


Yeah.  I think I'm following you.  The custom function would prompt
the user and then store the answer somewhere to keep from asking the
same questions again.  I'm thinking from the Genome perspective here.
I suspect we use Puppet slightly more iteratively than Thin Crust so
they ability to keep from asking the same questions every time Puppet
runs is nice.  


It's also nice to be able to figure out all the questions that are
going to be asked ahead of time so that the user doesn't have to watch
Puppet run.  I could see that being a little harder to implement
outside of Puppet though.