WIP ✨ (go/v4): Add support to Server-Side Apply

[camilamacedo86]

This PR adds a new ssa/v1-alpha plugin that scaffolds APIs with controllers using Kubernetes Server-Side Apply (SSA) patterns. How that works: See the doc added: https://deploy-preview-5458--kubebuilder.netlify.app/reference/server-side-apply.html

What is it?

Server-Side Apply helps when multiple actors (your controller, users, other controllers) need to manage different fields of the same resource. Instead of overwriting the entire object, SSA tracks field ownership and only updates the fields you explicitly manage.

Usage

# Initialize project                                      
kubebuilder init --domain example.com
                                                                                                
# Create API with SSA plugin
kubebuilder create api \                                                                        
  --group apps \                                                                                
  --version v1 \                                                                                
  --kind Application \                                                                          
  --ssa"                                                        
                                                                                                
# Generate apply configurations
make generate                                                                                   

What it scaffolds

1. API types with SSA markers - adds +genclient and +kubebuilder:ac:generate=true markers
2. Makefile updates - adds applyconfiguration generation (first time only)

After running make generate, you get type-safe apply configuration helpers:

  // Build desired state - only specify fields you want to manage                                 
  appApply := appsv1apply.Application(name, namespace).                                           
      WithSpec(appsv1apply.ApplicationSpec().                                                     
          WithReplicas(3))                                                                        
                                                                                                 
  // Apply - preserves fields managed by users/other controllers                                  
  r.Patch(ctx, app, client.Apply, client.ForceOwnership,                                          
      client.FieldOwner("my-controller"))                                                         

Closes: #2514
Closes: #5237

[yyewolf]

Just for my own culture, is proning client.ForceOwnership a result of "a single resource should not be managed by multiple operator" logic ?

[camilamacedo86]

Updated. Good catcher !!!

[k8s-ci-robot]

@camilamacedo86: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-kubebuilder-e2e-k8s-1-33-0	7bba449	link	true	/test pull-kubebuilder-e2e-k8s-1-33-0
pull-kubebuilder-e2e-k8s-1-36-0	e91383e	link	true	/test pull-kubebuilder-e2e-k8s-1-36-0
pull-kubebuilder-e2e-k8s-1-35-0	e91383e	link	true	/test pull-kubebuilder-e2e-k8s-1-35-0
pull-kubebuilder-e2e-k8s-1-34-0	e91383e	link	true	/test pull-kubebuilder-e2e-k8s-1-34-0

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[yyewolf]

I'm not quite sure on how to phrase it, but should we also say "Expect other people to automate your CRs through higher level operators" ?

As in the operator that has generated SSA types would not be the one using them but merely providing them for other operators to import ?

[yyewolf]

That's a really nice improvement, I can't wait to try it and we (at my company) will have a lot of work to do to use this as effectively as possible 🔥

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: camilamacedo86, yyewolf

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[Gentoli]

Stumbled on this PR while searching for recommendations on SSA for kubebuilder controllers. looks like client.Apply is deprecated. Is this still the way to do SSA?