[release-1.13] Fix scheduler panic when metrics are disabled

[Copilot]

What type of PR is this?

Bug fix (cherry-pick)

What this PR does / why we need it:

Manual cherry-pick of #4731 to release-1.13 branch.

Scheduler panics with nil pointer dereference when started without --enable-metrics=true. The k8s scheduler framework plugins unconditionally access k8smetrics.Goroutines, which was only initialized inside the metrics-enabled conditional block.

Change: Move metrics.InitKubeSchedulerRelatedMetrics() outside the conditional block so k8smetrics.Goroutines is always initialized:

// Before: only initialized when metrics enabled
if opt.EnableMetrics || opt.EnablePprof {
    metrics.InitKubeSchedulerRelatedMetrics()
    go startMetricsServer(opt)
}

// After: always initialize required metrics
metrics.InitKubeSchedulerRelatedMetrics()

if opt.EnableMetrics || opt.EnablePprof {
    go startMetricsServer(opt)
}

Which issue(s) this PR fixes:

Fixes #4729

Special notes for your reviewer:

The panic occurs in k8s.io/kubernetes/pkg/scheduler/framework/parallelize.Parallelizer.Until when calling Goroutines.WithLabelValues() on nil. This metric must be initialized regardless of whether metrics export is enabled.

Does this PR introduce a user-facing change?

Fix scheduler panic when starting without --enable-metrics=true flag

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[release-1.13] Fix scheduler panic when metrics are disabled</issue_title>
<issue_description>Manual cherrypick required.

#4731 failed to apply on top of branch "release-1.13":

Patch is empty.
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

```</issue_description>

## Comments on the Issue (you are @copilot in this section)

<comments>
</comments>

• Fixes [release-1.13] Fix scheduler panic when metrics are disabled #4768

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• 468dea3 Fix scheduler panic when metrics are disabled

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[JesseStutler]

/approve
/lgtm

[Copilot]

Pull request overview

This PR is a manual cherry-pick of #4731 to the release-1.13 branch, fixing a nil pointer dereference panic that occurs when the volcano scheduler starts without the --enable-metrics=true flag. The Kubernetes scheduler framework plugins unconditionally access k8smetrics.Goroutines, which was previously only initialized inside a conditional block.

Key changes:

• Move metrics.InitKubeSchedulerRelatedMetrics() outside the metrics/pprof conditional block to ensure it always executes
• Add explanatory comment documenting why this initialization must always occur

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[JesseStutler]

/approve

[volcano-sh-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: JesseStutler
Once this PR has been reviewed and has the lgtm label, please assign lowang-bh for approval. For more information see the Kubernetes Code Review Process.

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