General discussion about Chef

[chef] Re: Re: Re: Re: Populating attributes from the system.


Chronological Thread 
  • From: Bryant Lippert < >
  • To:
  • Subject: [chef] Re: Re: Re: Re: Populating attributes from the system.
  • Date: Tue, 8 Sep 2015 16:28:08 -0500
Hi Doug,

If you're looking for better documentation on Ohai, and working with it in Chef, consider Chapter 4 (Extending Ohai) from the book Customizing Chef (http://shop.oreilly.com/product/0636920032984.do). The rest of the book is pretty solid as well.

Best,
Bryant

On Tue, Sep 8, 2015 at 4:02 PM, Doug Garstang < " target="_blank"> > wrote:
Adam,

Actually I misspoke earlier. I'd forgotten about this. You can't access attributes from custom ohai plugins in attributes/ files. This is a pretty big deal. As far as I can see, there's no way to easily grab custom information from the system during the (is it the compile?) phase. 

This is what I did earlier, and it's pretty ugly.

#attributes/default.rb
def component_info
  #ruby code to get system info here
end

(component_name, component_group, release_branch, release_version) = component_info()

node['webapp']['version'] = release_version 

At least I can access that during the compile phase and derive other attributes from it. Isn't there a better way?

Doug.

On Tue, Sep 8, 2015 at 1:38 PM, Douglas Garstang < " target="_blank"> > wrote:
Adam,

I guess it feels wrong because I'm writing application specific things into something that's supposed to read to get system info. Our CloudFormation template is writing a file to the local filesystem that my chef cookbook needs to be able to read in order to know what branch, release etc of code to deploy. The custom ohai documentation is pretty slim as well, and it usually takes me a lot longer to get something working with ohai that it would a library.

Using the community ohai cookbook and also seeing this:

==> default: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/ohai-7.0.4/lib/ohai/plugins/linux/network.rb:49: warning: already initialized constant IPROUTE_INT_REGEX

Ohai just feels less well documented and maintained.

Doug.

On Tue, Sep 8, 2015 at 1:33 PM, Adam Leff < " target="_blank"> > wrote:
Doug-

If the data you're trying to extract is part of your system and not curated during a Chef run, I think Ohai is a perfect solution for this.  The first recipe in your nodes' run_lists could also deploy that Ohai plugin and reload it right away (if it needed to be deployed during that run) such that the rest of your chef-client run would have immediate access to the new plugin's data.

Could you elaborate as to why you do not feel the Ohai plugin approach is the right fit?

~Adam


On Tue, Sep 8, 2015 at 4:29 PM Doug Garstang < " target="_blank"> > wrote:
This problem keeps popping up, and it never feels quite right.

I need to extract some data from the system and populate node attributes from that, so that my cookbook will function.

If I use a library to get the system info, then I have move the setting of the attributes out of attributes/ files into a recipe, and make sure that recipe runs first. Any attributes that are derived from these attributes also have to be put into the same recipe. I then have some attributes being defined in attributes files and some recipes which doesn't feel right.

Writing an ohai plugin that pulls the system info means that the attributes are immediately available as ohai data when chef runs. This also feels like the wrong approach though.

What is the right way to do this?

Doug.





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