Decouple httptrigger and cronjob controllers from kubeless-controller-manager

[sayanh]

FEATURE REQUEST:
Currently, kubeless-controller-manager manages httptrigger and cronjob custom resources as well. Although kubeless supports a bunch of ingresses as httptriggers, users like us need something else. So in order to have an absolute decoupling of httptrigger and cronjobs, I propose to cut out httptrigger and cronjob from kubeless-controller-manager and have their own controllers. We can install these controllers in the out-of-box set up. But the real benefit of this will be to allow the power users to configure based on their needs and have an ala-carté experience altogether.

Additionally, it would be possible to rewrite custom controllers for these custom resources while keeping the kubeless-cli features(e.g. kubeless trigger) intact.

What happened:
If the CRDs for http-trigger and cronjobare not created(as they won't be used) then kubeless-controller-manager keeps spamming with a ton of errors:

E0528 13:35:58.382354       1 reflector.go:205] github.com/kubeless/kubeless/pkg/controller/cronjob_trigger_controller.go:133: Failed to list *v1beta1.CronJobTrigger: the server could not find the requested resource (get cronjobtriggers.kubeless.io)

Additionally, it is not possible to rewrite a custom controller for these custom resources.

Environment:

• Kubernetes version (use kubectl version): 1.8+
• Kubeless version (use kubeless version): v1.0.0-alpha.x

[andresmgot]

The idea here was to avoid having more deployments than the ones needed but I understand the point of not using HTTP or Cronjob triggers. cc/ @murali-reddy what do you think?

[murali-reddy]

I am fine to totally decouple, and install some trigger controllers (http trigger perhaps) by default so users can quickly try Kubeless.

@sayanh would you like to give a try? Should be failry easy they are already seperate components except they are rolled into same binary, deployment etc.

[sayanh]

@murali-reddy sounds good

[murali-reddy]

@sayanh may be this can rolled into #695 which i am working on it

[andresmgot]

So with #871 HTTP and cronjob triggers have their own controller that run in an independent container in the controller pod.