[Mitch Connors (therealmitchconnors)]

What type of PR is this?

/kind feature
/kind api-change

What this PR does / why we need it:

Adds a new hub controller that deploys and manages Azure Global Load
Balancers (GLBs) for MultiClusterLoadBalancer resources, built on an
istio.io/istio/pkg/kube/krt-based reconciliation pipeline. Alongside
the controller, this PR introduces real client-gen/
applyconfiguration-gen/openapi-gen codegen tooling, reducing the
amount of code required to build and test the controller substantially.

🚧 This PR is a draft. It is not ready to merge — opening it now to
get early feedback on direction (especially the krt-based pipeline and
the codegen approach) before polishing further.

Which issue(s) this PR fixes:

Fixes #

---

How to review this PR

This PR is organized as 3 commits, each a self-contained concern.
Please review commit-by-commit (GitHub's "Commits" tab, or
git log -p --first-parent) rather than the full squashed diff — the
full diff is large (~90 files) but almost all of it is generated code
that doesn't need line-by-line review.

#	Commit	What it is	Review priority
1	943277d Add real API-schema codegen tooling...	Makefile codegen targets, the openapi-schema-gen entrypoint, hand-written API types/markers (incl. the new MultiClusterLoadBalancer type), go.mod/go.sum	Please review — this is hand-written infra
2	fd818f9 Regenerate clientset, apply-configurations, and OpenAPI schema...	Mechanical output of make generate using the tooling from commit 1: zz_generated.deepcopy.go, CRD YAML, pkg/applyconfigurations/**, pkg/generated/**	Skip — generated, marked linguist-generated in .gitattributes so GitHub collapses it by default in "Files changed"
3	5cba71a Add Global Load Balancer controller with krt-based kube client	The actual feature: pkg/controllers/hub/globalserviceexport (the GLB controller), pkg/apiclient (the krt-compatible kube client wrapper), tests, and docs	Please review — this is the point of the PR

If your GitHub diff view isn't collapsing the generated files automatically, you can also view just the reviewable surface with:

git diff 943277d~1..5cba71a -- . ':!pkg/generated' ':!pkg/applyconfigurations' ':!*/zz_generated.*' ':!config/crd/bases'

Suggested reading order

1. docs/concepts/GlobalLoadBalancer/architecture.md and docs/concepts/KrtApiClient/README.md for context before diving into code.
2. pkg/apiclient/ (small, ~2 files) — the kube client wrapper the controller depends on.
3. pkg/controllers/hub/globalserviceexport/controller.go — the controller itself. Notable things to look at:
   • The krt-based transformation pipeline and the async deployment work queue (non-blocking writes off the transform hot path).
   • fieldManagerName vs statusFieldManagerName — separate field managers for main-resource vs. status-subresource Apply calls (needed to avoid one clobbering the other's managed fields).
   • The Recorder-based Kubernetes event emitted on deployment failure.
4. pkg/controllers/hub/globalserviceexport/controller_test.go for coverage of the above.

Requirements:

• run make reviewable for basic local test (note: make lint/make staticcheck could not be run in the dev sandbox due to a Go toolchain version mismatch with the pinned tool versions — please run these in CI/locally before merge)
• Read and followed fleet-networking's Code of conduct.
• uses conventional commit messages
• includes documentation
• adds unit tests

How has this code been tested

• go build ./... and go vet ./... pass across the repo.
• go test -v -race ./pkg/controllers/hub/globalserviceexport/... passes, including the new async-deployment-queue and event-emission tests.

Special notes for your reviewer

• This is a draft PR. Expect rough edges — in particular the krt/controller-runtime coexistence pattern and the hardcoded ARM-related values in the controller are likely to need discussion before this is merge-ready.
• Generated-file commit (fd818f9) is large by line count but mechanical; please focus review time on commits 1 and 3.

[codecov]

Codecov Report

❌ Patch coverage is 16.90402% with 1342 lines in your changes missing coverage. Please review.
✅ Project coverage is 11.64%. Comparing base (76f455e) to head (ae9fa8e).

Files with missing lines	Patch %	Lines
...nfigurations/api/v1alpha1/internalserviceexport.go	0.00%	109 Missing ⚠️
...nfigurations/api/v1alpha1/internalserviceimport.go	0.00%	109 Missing ⚠️
...gurations/api/v1alpha1/multiclusterloadbalancer.go	0.00%	106 Missing ⚠️
.../applyconfigurations/api/v1alpha1/serviceexport.go	0.00%	106 Missing ⚠️
.../applyconfigurations/api/v1alpha1/serviceimport.go	0.00%	106 Missing ⚠️
...g/applyconfigurations/api/v1beta1/serviceexport.go	0.00%	106 Missing ⚠️
.../controllers/hub/globalserviceexport/controller.go	80.59%	43 Missing and 22 partials ⚠️
...tset/internalclientset/fake/clientset_generated.go	0.00%	50 Missing ⚠️
...generated/clientset/internalclientset/clientset.go	0.00%	45 Missing ⚠️
...internalclientset/typed/api/v1alpha1/api_client.go	0.00%	42 Missing ⚠️
... and 33 more

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #418       +/-   ##
===========================================
- Coverage   67.06%   11.64%   -55.43%     
===========================================
  Files          34       77       +43     
  Lines        3859    24480    +20621     
===========================================
+ Hits         2588     2850      +262     
- Misses       1090    21426    +20336     
- Partials      181      204       +23     

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