[chef] Re: Re: Re: Re: Template attributes - converge time vs. run time

[Michael Glenney < >]

Awesome guys.  Thanks!  I went with the "lazy" method because it's less syntax but tried them both out and they both work.

Cassiano, I wondered the same thing.  They looked the same.  Almost as if "lazy" was just an alias for the helper.  From what I can see:

1)  Helper is much more powerful.  Especially the way it can take arguments.  I think the fact that it will allow you to use cookbook library modules is also unique.

2)  Helpers are limited to template resources whereas lazy can be used anywhere

Other then that they are very similar and I'll be share some code.

It did prompt me to learn about "Lazy evaluation" http://en.wikipedia.org/wiki/Lazy_evaluation which I didn't know about before so thanks for that :)

Here's what I ended up with which worked perfectly:

template "/etc/security/access.conf" do

  source "access.conf.erb"

  mode 0440

  owner "root"

  variables(

    :access_groups => lazy { node['authorization']['access']['groups'] },

    :access_users => lazy { node['authorization']['access']['users'] }

  )

  action :nothing

end

# This resource exists purely to notify the above resource to run near the end of the chef run

execute "true" do

  notifies :create, 'template[/etc/security/access.conf]', :delayed

end

Thanks again !!

MG

On Thu, Oct 17, 2013 at 1:22 PM, Cassiano Leal < " target="_blank"> > wrote:

This is interesting. What would be the difference between the two methods (lazy vs helper)?

--

Cassiano Leal

http://cassianoleal.com

http://twitter.com/cassianoleal

On Thursday, October 17, 2013 at 14:08, Daniel DeLeo wrote:

On Wednesday, October 16, 2013 at 5:37 PM, Cassiano Leal wrote:

I believe this http://docs.opscode.com/release_notes.html#lazy-attribute-evaluation is what you’re looking for.

On Wednesday, October 16, 2013 at 21:16, Michael Glenney wrote:

I noticed when I pass attributes to a template resource via the 'variables' attribute the attributes values are what they are at converge time.  So if I modify those attributes during the chef run, before the template resource get's called, it doesn't matter.  They get rendered as they were at converge time.

The only way around this I've found is to NOT pass the attributes via the 'variables' attribute and instead source them directly in the template.  I don't like doing that.  I like having everything that's being passed to the template defined in the recipe for documentation purposes.

Is there any way around this?  The attribute is correct in memory at the time the template resource is called.  Is there any way to tell it to use the attribute in memory instead of how it was at converge time?  Or am I stuck calling them from within the template?

MG

You can also use template helpers to keep your logic separate from your templates:

http://docs.opscode.com/resource_template.html#helpers 

-- 

Daniel DeLeo