feat(metrics): expose queue guarantee resource metrics

[Aman-Cool]

What type of PR is this?
/kind feature

What this PR does / why we need it:

guarantee is the one queueAttr field that actually represents a contractual SLA; it floors deserved in proportion and blocks reclaim from evicting a queue below its minimum in capacity; but it never made it into Prometheus. Every other field that drives a scheduling decision has a metric. This one didn't.

Adds volcano_queue_guarantee_{milli_cpu,memory_bytes,scalar_resources} emitted each session from both plugins. Jobless queues still get the metric read straight from the queue spec, same pattern as the no-attr branch in capacity already uses for realCapacity. Hierarchical queues get it for free since attr.guarantee already accumulates child guarantees by the time we hit the metrics loop. DeleteQueueMetrics cleans it up.

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

Special notes for your reviewer:

The no-attr branch in proportion now does a small spec read to get the guarantee for queues with no jobs; same thing capacity's no-attr branch already does for realCapacity at the equivalent spot, so the pattern is consistent. Everything else is a straight copy of the inqueue metric shape.

AI Disclosure: This change was developed with AI assistance (Claude). The author has reviewed and understands all changes.

Does this PR introduce a user-facing change?

Added Prometheus metrics for queue guarantee resources: volcano_queue_guarantee_milli_cpu, volcano_queue_guarantee_memory_bytes, and volcano_queue_guarantee_scalar_resources. Emitted by both proportion and capacity plugins.

[gemini-code-assist]

Code Review

This pull request introduces new Prometheus metrics to track guaranteed resources (CPU, memory, and scalar resources) for queues in the Volcano scheduler. It adds the UpdateQueueGuarantee function to the metrics package, integrates it into the capacity and proportion plugins, and includes comprehensive unit tests to verify the recording and deletion of these metrics. I have no feedback to provide.

[Copilot]

Pull request overview

This PR adds Prometheus gauge metrics to expose per-queue guarantee resources (CPU, memory, and scalar resources), so that the queue’s minimum/SLA-like floor is observable alongside other scheduling-driving queue attributes.

Changes:

• Add new metrics: volcano_queue_guarantee_milli_cpu, volcano_queue_guarantee_memory_bytes, volcano_queue_guarantee_scalar_resources.
• Emit guarantee metrics from both proportion and capacity scheduler plugins (including “no jobs in queue” paths).
• Ensure DeleteQueueMetrics also removes the new guarantee metrics, and extend unit tests to validate presence and cleanup.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
pkg/scheduler/plugins/proportion/proportion.go	Emit queue guarantee metrics for queues with and without in-session attributes.
pkg/scheduler/plugins/capacity/capacity.go	Emit queue guarantee metrics for both flat and hierarchical queue attribute builders.
pkg/scheduler/metrics/queue.go	Define guarantee gauge vectors, add UpdateQueueGuarantee, and delete guarantee metrics in DeleteQueueMetrics.
pkg/scheduler/metrics/queue_test.go	Extend existing HTTP-scrape metrics test to assert guarantee metrics are emitted and deleted.
pkg/scheduler/metrics/queue_scalar_test.go	Add scalar-resource behavior test coverage for UpdateQueueGuarantee (zeroing and cleanup).

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[Aman-Cool]

@hajnalmt @JesseStutler @hzxuzhonghu,One thing I want to flag proactively: The tests only verify the metrics layer (UpdateQueueGuarantee sets and deletes correctly); they don't exercise the actual call sites in proportion.go and capacity.go.
A typo at the plugin level (wrong field, wrong variable) wouldn't be caught. This is consistent with how every other queue metric is tested in the repo, so I kept it that way here, but it's a real gap. Happy to add plugin-level tests in a follow-up if you guys prefer it addressed now😄.

[Aman-Cool]

/assign @hajnalmt

[Copilot]

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

[Aman-Cool]

/assign @JesseStutler