[chef] Re: Re: Re: Re: Programmatic creation/deletion of resources

[Simon Detheridge < >]

>> Thanks, that is very much what I'm looking for.
>>  
>> Follow-up: My resource has a fairly large number of potential attributes. 
>> Is
>> there a way I can set them in a less DSL-like way? For example:
>>  
>> nxlog_source "name" do
>> {"hash": "with", "a": "bunch", "of": "pairs"}.each_pair do |k,v|
>> set_attribute k, v
>> end
>> end
>>  
>> as opposed to
>>  
>> resource_attr1 node_attrs["resource_attr1"]
>> ...
>> resource_attr50 node_attrs["resource_attr50"]
>>  
>> This way I can not repeat myself and avoid having to maintain a file with
>> another list of my resource attributes...

> You can use Ruby’s #public_send method to call methods that you don’t know 
> the
> name of ahead of time. (There is also #send, but that can call private 
> methods,
> so you shouldn’t use it unless you really have to).
> 
> http://ruby-doc.org/core-2.1.1/Object.html#method-i-public_send

That's great, thanks.

>> > > - How do I enumerate currently-extant resources so that I can delete 
>> > > ones that
>> > > have been removed? (or... is this even possible?)
>> > >  
>> > > for example: If I've removed an element from the 'sources' array how 
>> > > can I
>> > > ensure that the resource's config file is cleaned up on the node?

>> > What thing on the system represents the stuff that exists? Are these 
>> > individual
>> > files (sounds like yes)? As long as there aren’t unmanaged files in that
>> > particular directory, you can use Ruby’s Dir.glob to enumerate the 
>> > existing
>> > files and compare to the list of things you want, and remove the extra
>> > elements.

>> Yeah, it's files in a conf.d. I think the issue that I'm grappling with is 
>> that
>> let's say someone has used node attributes to create a source, but 
>> elsewhere
>> someone has used a lwrp to create a different source in another recipe... 
>> How
>> can I ensure I don't clean up the source that's been defined via the lwrp
>> instead of the node attributes?

> You can’t do it perfectly in all cases, but if all changes to files in that 
> dir
> occur via core chef resources (file, template, etc.) then you can inspect 
> the
> resource collection to find orphaned files. The “zap” cookbook does this, 
> you
> can maybe use it directly or read the code for inspiration:
> https://github.com/nvwls/zap

Perfect. Yes, it uses standard Chef templates which would become orphaned 
when the attributes are removed from the node. I'll take a look at 'zap'.

Thanks for all your help.

-- 
Simon Detheridge - CTO, Widgit Software
26 Queen Street, Cubbington, CV32 7NA - Tel: +44 (0)1926 333680