[chef] Antwort: Re: Antwort: Re: Testing idempotence of chef cookbooks

Ok, I see. Well maybe I understood something
wrong, but from my understanding idempotence is the property when you apply
a cookbook several times and the result is always the same. So I always
thought it is enough to run converge multiple times and see if the serverspec
tests are always the same. That is also something you can easily automate
for a CI environment.

The property that only resources are
updated that are really needed is more some kind of efficiency of cookbooks,
isn't it? 

And as you described it is not always
possible to have "0 resources updated" so I wonder if such idempotence
tests can be standardized or automated at all.





Von:      
 Roland Moriz <
 >
An:      
 
 
Datum:      
 22.05.2015 04:34
Betreff:    
   [chef] Re: Antwort:
Re: Testing idempotence of chef cookbooks

---

Am 21.05.2015 um 17:30 schrieb Ranjib Dey <
 
 ">
 >:

yeah, its should be 0 resources updated if everything
is idempotent and already converged. those two numbers relfect number of
updated resources / number of total resources. Total resources is sum of
all resources defined by all recipes, lwrps as part of the expanded run
list, while updated resources are a subset of them which was modified (like
absent file being created, absent packaged being installed etc) during
the chef run.


Some resources are very hard to make „chef-idempotent“,
e.g. ruby blocks. Even if you make sure your ruby code is idempotent, the
execution of the block already counts as „updated resource“. Even popular
community cookbooks do have that "problem“.  

You probably want to add each converge result to a temp
file and calculate/check the difference or some kind of percentage instead.

regards
Roland




On Thu, May 21, 2015 at 8:01 AM, <
 
 " target=_blank>
 >
wrote:
Isn't your way the same as running the
converge command twice and looking at the last line of the chef-client
output? If so, this way sounds a little bit easier for me.

        Chef Client finished, 45/61 resources updated
in 16.28070151 seconds 

If so, what is really the goal of testing idempotence? Should I really
have a "0 resources updated"? 
By the way, what do the two numbers mean actually?

regards, 
Johannes 




Von:        Roland
Moriz <
 
 " target=_blank>
 >
An:        
 
 " target=_blank>
 
Datum:        20.05.2015
13:10 
Betreff:        [chef]
Re: Testing idempotence of chef cookbooks

---

Hi, 


Am 20.05.2015 um 10:21 schrieb 
 
 " target=_blank>
 :

Hi, 

is there a general way or best practice for testing idempotence of chef
cookbooks? 


An approach might be to use test-kitchen + duplicate suite names + a custom
chef-handler that writes the number of updated resources to disk + serverspec
to verify it. 

e.g. .kitchen.yaml 

-8<--- 
suites: 
  - name: default 
    run_list: 
      - recipe[chef-handler] 
      - recipe[build-essential] 
    attributes: 

  - name: default 
    run_list: 
      - recipe[chef-handler] 
      - recipe[build-essential] 
    attributes: 
-8<--- 

this will converge the node twice on „kitchen converge“. 

An example for a simple chef handler: https://github.com/jtimberman/chef-handler-updated-resources/blob/master/lib/chef/handler/updated_resources.rb
- use https://supermarket.chef.io/cookbooks/chef_handler
to deploy the handler to your testing node. 

Instead of logging to Chef::Log you could just write the number of updated
resources to a log file e.g. /tmp/updated_resources and use http://serverspec.org/resource_types.html#file
to verify. 

hth 

best regards 
Roland