[katello-devel] some thoughts on foreman-architectures branch

[Dmitri Dolguikh]

The logic used to access Foreman server is spread over several classes: 
a bunch of automatically-generated proxy-type classes that reside in 
foreman_api gem, ForemanModel (resides in 
lib/resources/foreman_model.rb), that is a base-class for Foreman 
resource classes that reside in app/models/foreman.

Good things first:
  - app/models/foreman classes are minimal, and clearly show what 
attributes are being used.
  - app/models/foreman classes allow for local validation via standard 
ActiveModel validators.
  - app/models/foreman classes allow for easy customization of json 
generation.


Things I don't like:
  - I can't shake the feeling that the approach represented in the 
branch is a huge duplication of effort. We are replicating 
ActiveResource on every step of the way, and:
   - ActiveResource's error handling is better/consistent (ours is 
minimal and current approach would require us to recreate all of 
RestClient's exceptions)
   - ActiveResource's error parsing is much better (we'll have to 
duplicate AR's code to be able to parse remote errors).
   - Pretty much all of ForemanModel is what we'd get with 
ActiveResource for free. Keep in mind that custom methods are simple 
with ActiveResource.
  - Foreman uses rabl [1] for json-generation, we implemented a custom 
approach. I think rabl is at least worth a look.
  - Apipie in it's current shape promotes code duplication. See 
foreman_api classes, domain- and architectures-controllers in katello.


I propose:
  - It's been close to a couple of years since we looked at 
ActiveResource last. I'd like to see where it is now, how hard it is to 
use with oauth and non-rails types of resource urls these days.
  - I'd like to evaluate rabl for use in Katello
  - I'd like to fix code duplication issues in Apipie, possibly switch 
it to use ActiveResource instead of RestClient


-d


[1] https://github.com/nesquena/rabl <https://github.com/nesquena/rabl>


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