refactor(kubeclient): consolidate duplicate code

[ivankatliarchuk]

What does it do ?

Create a new pkg/kubeclient package to consolidate duplicate Kubernetes client creation logic, add metrics instrumentation to the events controller, and use the.

tested here #6099. all works without issues

1. New centralized package pkg/client/config.go
   • added tests
2. Removed duplicate code from:
   • source/store.go
   • pkg/events/controller.go
3. Events client now uses shared clientset

How kube client created and shared with different packages

flowchart TD
    A[externaldns.Config] -->|passed to| B[source.NewClientGenerator]
    B -->|creates| C[SingletonClientGenerator]

    C -->|used by| D[buildController]
    C -->|used by| E[buildSource]

    D -->|calls| F[clientGen.EventsClient]
    F -->|returns| G[EventsV1Interface]
    G -->|passed to| H[events.NewEventController]

    E -->|calls| I[source.ByNames]
    I -->|calls| J[clientGen.KubeClient]
    J -->|returns| K[kubernetes.Interface]
    K -->|used by| L[Sources<br/>Service/Ingress/etc]

    subgraph "Shared Client"
        C
        M[clientGen.KubeClient] -->|creates once| N[kubernetes.Clientset]
        F2[clientGen.EventsClient] -->|delegates to| N
        N -->|.EventsV1| G2[EventsV1Interface]

        style N fill:#99ccff
    end

    style C fill:#ffcc99
    style H fill:#99ff99
    style L fill:#99ff99

Loading

Follow-up

• better test coverate
• support events for all sources

Motivation

Currently event generator and source have 2 distinct clients. As a result rate limiting not working as it should on clusters with large ~50k records.

• Eliminates 3 copies of the same REST config/client creation logic
• Shared connection pool: Events client now shares HTTP transport and rate limiter with other K8s clients, preventing independent rate limit exhaustion
• Consistent instrumentation: All clients now guaranteed to have the same Prometheus metrics wrapper
• Future changes to kube client config (timeouts, TLS, etc.) only need one update

Work relates to

• Add Record Creation Status to Source Object #6030
• previous PR feat(events): raise k8s events with fake provider #5659
• previous pr refactor(controller): controller no longer responsible for SingletonClientGenerator creation #6077

More

• Yes, this PR title follows Conventional Commits
• Yes, I added unit tests
• Yes, I updated end user documentation accordingly

Follow up:

• refactor(kubeclient): consolidate duplicate code #6076 (comment)

[coveralls]

Pull Request Test Coverage Report for Build 21311701509

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 473 unchanged lines in 23 files lost coverage.
• Overall coverage increased (+0.06%) to 79.129%

---

Files with Coverage Reduction	New Missed Lines	%
fake.go	1	96.23%
annotations/processors.go	2	97.26%
zonefinder.go	3	90.0%
events/types.go	9	90.44%
execute.go	9	59.94%
node.go	9	90.24%
controller.go	9	92.56%
events/controller.go	10	77.33%
crd.go	10	66.45%
gen/docs/sources/main.go	13	81.7%

Totals
Change from base Build 21060483362:	0.06%
Covered Lines:	16030
Relevant Lines:	20258

---

💛 - Coveralls

[vflaux]

Just small nitpicks, but LGTM.

[vflaux]

Not used but I assume it's related to the TODO of GetRestConfig?
https://github.com/gofogo/k8s-sigs-external-dns-fork/blob/22008dc0327142b1e717b38c945edd0604692216/pkg/client/config.go#L40

Was this committed by mistake?

[ivankatliarchuk]

Yep. Removed. The code works at least on my setups, just not sure what the potential edge cases are

[ivankatliarchuk]

Hola @vflaux. Is there anything left or we are good to go?

[vflaux]

/lgtm

[ivankatliarchuk]

/approve

[k8s-ci-robot]

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