docs: document Prometheus metrics exposed by vGPU monitor

[khanskr]

What type of PR is this?
/kind documentation

What this PR does / why we need it:
Adds docs/metrics.md documenting the Prometheus metrics exposed by the vGPU monitor (vGPUmonitor), including a description of each metric and example PromQL queries, as requested in issue #2356.

Which issue(s) this PR fixes:
Fixes #2356

Special notes for your reviewer:
Metric names, types, labels and value semantics were verified against the descriptors and collection code in cmd/vGPUmonitor/metrics.go and pkg/metrics/metrics.go. The bind address and legacy-metrics flags are documented from cmd/vGPUmonitor/main.go, and the scrape service configuration from the helm chart.

AI assistance disclosure:
The PR description was generated with AI assistance. No other part of this PR was generated with AI. I reviewed the change and take responsibility for it.

Does this PR introduce a user-facing change?:
NONE

Summary by CodeRabbit

• Documentation
  • Added comprehensive guidance for the HAMi vGPU monitor.
  • Documented deployment behavior, metrics endpoint configuration, Helm access, and Prometheus scraping.
  • Explained per-node scraping considerations, metric labels, and metric semantics.
  • Documented legacy metric compatibility and provided example PromQL queries for monitoring and analysis.

[hami-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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

The full list of commands accepted by this bot can be found here.

Details

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• OWNERS

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[hami-robot]

Welcome @khanskr! It looks like this is your first PR to Project-HAMi/HAMi 🎉

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 1e4e992b-b13b-40df-ba6f-97eee0ed52a8

📥 Commits

Reviewing files that changed from the base of the PR and between 46a80e5 and a4ac385.

📒 Files selected for processing (1)

• docs/metrics.md

🚧 Files skipped from review as they are similar to previous changes (1)

• docs/metrics.md

---

📝 Walkthrough

Walkthrough

Added docs/metrics.md with vGPU monitor access instructions, metric definitions, legacy compatibility details, and PromQL examples.

Changes

vGPU monitor metrics documentation

Layer / File(s)	Summary
Monitor access and scraping docs/metrics.md	Documents DaemonSet deployment, data sources, endpoint configuration, Helm access, Prometheus scraping, per-node behavior, and metric labels.
Metric reference and queries docs/metrics.md	Describes GPU, vGPU, MIG, unified-memory, kernel, and legacy metrics. Adds PromQL examples for monitoring queries.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Possibly related PRs

• Project-HAMi/HAMi#1990: Exposes the vGPU monitor metrics port documented here.
• Project-HAMi/HAMi#2142: Modifies vGPU metrics and labels described here.
• Project-HAMi/HAMi#2153: Implements node-label changes covered by this documentation.

Suggested reviewers: archlitchi, ouyangluwei163

Poem

A rabbit reads the metrics bright,
PromQL hops from left to right.
GPU labels now align,
MIG and vGPU metrics shine.
The monitor charts the night.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the added documentation for Prometheus metrics exposed by the vGPU monitor.
Linked Issues check	✅ Passed	The documentation covers the vGPU monitor metrics, descriptions, labels, semantics, and example PromQL queries required by issue [#2356].
Out of Scope Changes check	✅ Passed	The changes are limited to documentation for vGPU monitor metrics, scraping configuration, compatibility, and related usage guidance.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@docs/metrics.md`:
- Around line 28-35: Update the Prometheus scraping example in the metrics
documentation to use the chart-generated ServiceMonitor instead of directly
scraping the NodePort address, or explicitly document that the NodePort Service
must use externalTrafficPolicy: Local for per-node scraping.

🪄 Autofix

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: d1a362a4-7de1-4a66-9df2-0cda55568b4a

📥 Commits

Reviewing files that changed from the base of the PR and between 2cabe29 and 46a80e5.

📒 Files selected for processing (1)

• docs/metrics.md

[archlitchi]

docs/ only contains design document, for user-guide, you need to change the hami-website:https://github.com/Project-HAMi/website