[sohankunkerkar]

What type of PR is this?

/kind feature
/area tas
/area dra

What this PR does / why we need it?

Quota limits how many devices a CQ admits, not where those devices are. A Workload whose ResourceClaims no single node can satisfy is admitted on quota alone; Kueue removes the scheduling gate, kube-scheduler finds no node that can allocate the claims, and the Pods stay Pending while the Workload holds quota.

Kueue now evaluates device availability per node before admission and treats a node that cannot satisfy the claims as unavailable, so a Workload that no node can serve stays queued and its quota stays free.

Part of: #10548

Useful notes for your reviewer

Release note

DRA: Added the `KueueDRADeviceFeasibility` feature gate, Alpha and disabled by default. Kueue checks device availability per node before admitting a Workload that uses ResourceClaimTemplates or DRA-backed extended resources, so quota is not reserved for a Workload kube-scheduler cannot place.

AI summary

Adds per-node DRA device feasibility checks before Workload admission. When KueueDRADeviceFeasibility is enabled, infeasible Workloads remain queued and retain quota. The change also adds TAS exclusion reporting and DRA-aware simulator, cache, and integration test coverage.

Suggested release note

DRA: Added per-node device feasibility checks so Kueue keeps Workloads queued when no node can satisfy their ResourceClaims or DRA-backed extended-resource requests. This behavior is controlled by the KueueDRADeviceFeasibility feature gate.

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📝 Walkthrough

Walkthrough

The PR adds an Alpha KueueDRADeviceFeasibility gate. Enabled snapshots use DRAChecker to filter nodes with Kubernetes DRA allocation state. TAS reports DRA no-fit results, and WAS integration tests cover feasible, exhausted, repeated, and non-DRA workloads.

Changes

DRA feature and simulator wiring

Layer / File(s)	Summary
Feature gate, cache, and simulator wiring cmd/kueue/main.go, pkg/cache/scheduler/..., pkg/dra/..., pkg/features/..., pkg/scheduler/flavorassigner/..., pkg/cache/scheduler/was/..., site/data/..., test/compatibility_lifecycle/...	Adds the DRA feasibility gate, propagates DRA-backed resource caches, resolves DeviceClasses, supports WAS options, and delegates DRA-backed resources to per-node checks instead of TAS domain capacity.

DRA feasibility checker

Layer / File(s)	Summary
Allocator-backed node filtering pkg/cache/scheduler/simulator/dra_feasibility.go, pkg/cache/scheduler/simulator/types.go, pkg/cache/scheduler/snapshot.go, pkg/cache/scheduler/snapshot_test.go, pkg/util/testing/wrappers.go, pkg/cache/scheduler/simulator/dra_feasibility_test.go	Adds claim resolution, extended-resource claim synthesis, cached allocator construction, candidate filtering, context handling, and DRANoFit tracking. Tests cover claims, extended resources, capacity, binding, allocation state, and snapshot reuse.

TAS integration

Layer / File(s)	Summary
Topology assignment and exclusion reporting pkg/cache/scheduler/tas_flavor_snapshot.go, pkg/cache/scheduler/tas_flavor_snapshot_test.go, pkg/cache/scheduler/tas_cache_test.go, pkg/config/validation_test.go	Passes Workload namespaces to pod requirements, reports and aggregates DRA exclusions, and tests DRA-aware TAS placement and feature-gate dependencies.

WAS integration scenarios

Layer / File(s)	Summary
DRA scheduling integration suite test/integration/singlecluster/scheduler/was/...	Configures DRA-enabled WAS scheduling and verifies placement on device-publishing nodes, repeated extended-resource admission, pending oversized claims, and non-DRA admission.

Priority: ➖ Normal

Estimated code review effort: 4 (Complex) | ~60 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant Workload
  participant TASFlavorCache
  participant DRAChecker
  participant DRAAllocator
  participant Node
  Workload->>TASFlavorCache: build pod requirements
  TASFlavorCache->>DRAChecker: find feasible nodes
  DRAChecker->>DRAAllocator: evaluate claims on each node
  DRAAllocator->>Node: inspect ResourceSlices and allocations
  DRAAllocator-->>DRAChecker: feasible node or no fit
  DRAChecker-->>TASFlavorCache: candidates and DRANoFit counts

Loading

Merge Risk: 🟡 Moderate · up to 81f32

When this Alpha feature is enabled, a DRA workload can be admitted with more replicas assigned to a node than its devices support. Preemption and transient cancellation paths can also incorrectly reject otherwise feasible placements. These correctness gaps should be resolved before merge.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 48.72% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 39 functions across 22 files. (2 skipped:…	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 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 main change: checking DRA device availability per node before Workload admission.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 48.72% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 39 functions across 22 files. (2 skipped: 2 unsupported.)

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[Copilot]

🟡 Changes recommended

Three critical findings and one moderate finding remain unresolved.

Get a fresh assessment by requesting another Copilot review.

Pull request overview

Adds Alpha-gated, per-node DRA device feasibility checks before WAS/TAS admission.

Changes:

• Integrates structured DRA allocation into WAS and TAS.
• Adds feature-gate wiring and lifecycle metadata.
• Adds tests, helpers, and KEP documentation.

Review findings:

• Critical (2 votes): dra_feasibility.go bypasses taint-rule-patched ResourceSlices.
• Critical (2 votes): DRA checks do not account for all workload replicas.
• Moderate (1 vote): WAS does not retry feasibility when DRA inputs change.
• Critical (2 votes): DRA feasibility is not enforced when per-node TAS feasibility is disabled.

File summaries

File	Summary
test/integration/singlecluster/scheduler/was/was_test.go	Adds DRA/TAS integration scenarios.
test/integration/singlecluster/scheduler/was/suite_test.go	Configures integration-suite DRA/TAS support.
test/compatibility_lifecycle/reference/versioned_feature_list.yaml	Updates feature lifecycle metadata.
site/data/featuregates/versioned_feature_list.yaml	Publishes feature-gate metadata.
pkg/util/testing/wrappers.go	Adds a ResourceSlice node helper.
pkg/features/kube_features.go	Defines the DRA feasibility feature gate.
pkg/cache/scheduler/was/scheduling_simulator.go	Integrates DRA feasibility into WAS.
pkg/cache/scheduler/was/scheduling_simulator_test.go	Tests WAS DRA option wiring.
pkg/cache/scheduler/was/scheduling_simulator_stub.go	Maintains stub compatibility.
pkg/cache/scheduler/tas_flavor_snapshot.go	Propagates DRA-related TAS data.
pkg/cache/scheduler/tas_flavor_snapshot_test.go	Tests TAS/DRA integration.
pkg/cache/scheduler/simulator/types.go	Adds DRA exclusion statistics.
pkg/cache/scheduler/simulator/dra_feasibility.go	Implements per-node DRA feasibility checks.
pkg/cache/scheduler/simulator/dra_feasibility_test.go	Tests allocator feasibility behavior.
keps/2941-DRA/README.md	Documents the feature and lifecycle.
cmd/kueue/main.go	Wires feature-gated DRA checking.

Review details

Suppressed comments (4)

pkg/cache/scheduler/simulator/dra_feasibility.go:196

• DeviceBindingAndStatus is enabled from DRADeviceBindingConditions alone, but the structured allocator used by kube-scheduler enables this mode only when both DRADeviceBindingConditions and DRAResourceClaimDeviceStatus are enabled. With only the former gate set, Kueue can select a device that kube-scheduler will not consider feasible, defeating the stated same-allocation behavior.

		DeviceBindingAndStatus: utilfeature.DefaultFeatureGate.Enabled(features.DRADeviceBindingConditions),

pkg/cache/scheduler/simulator/dra_feasibility.go:172

• The structured allocator contract treats non-context errors from Allocate as fatal invalid-input/configuration errors that the scheduler must report, not as a node-specific no-fit result. Continuing after such an error can hide malformed CEL or other cluster configuration and admit on a different node; return the error instead of incrementing DRANoFit.

		if err != nil {
			if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
				return nil, err
			}
			// A failure usually means broken cluster configuration, such as a

pkg/cache/scheduler/simulator/dra_feasibility.go:244

• A ResourceClaimName can refer to a claim that already has Status.Allocation. Returning only its Spec turns that claim into a new allocation request, while buildAllocatedState has already marked the existing devices occupied; the allocator can therefore reject the node owning the claim or choose a different node. kube-scheduler instead derives availability from the existing allocation, so named allocated claims need to preserve/use their allocation and node selector here.

		return &claim.Spec, nil

pkg/cache/scheduler/was/scheduling_simulator.go:210

• Wrapping each snapshot with DRAChecker does not cause a new admission attempt when device state changes. The existing ResourceSlice controller only accepts events for configured counter/capacity drivers, so a mapping with only DeviceClassNames can leave a workload parked inadmissible after a matching ResourceSlice is created (and DeviceClass/taint-rule changes have the same gap). Add event handling that retries pending feasibility-checked workloads whenever their DRA inputs change.

	if s.draEnabled {
		return simulator.NewDRAChecker(snapshot, s.cl), nil
	}

• Files reviewed: 16/16 changed files
• Comments generated: 3
• Review effort level: Lite

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Actionable comments posted: 4

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Inline comments:
In `@pkg/cache/scheduler/simulator/dra_feasibility.go`:
- Around line 239-244: Update the named-ResourceClaim handling around the
ResourceClaim lookup to preserve an existing claim.Status.Allocation and its
node constraints instead of returning only claim.Spec. Ensure
buildSyntheticClaims sends only unallocated claims to the allocator, while
buildAllocatedState continues treating existing allocations as consumed; retain
the current lookup error behavior.
- Line 167: Update the TAS feasibility flow around fillInCounts,
DRAChecker.filterByDevices, and fillLeafCounts to track cumulative per-node DRA
capacity across synthetic claims instead of treating each Allocate call as
independent. Expose each node’s remaining DRA capacity to TAS and cap that
node’s podCount before topology assignment, preserving capacity accounting
separately for each node rather than applying only a cluster-wide replica limit.
- Around line 86-90: Update DRAChecker.PreemptWorkload and the corresponding
rollback path used by simulated preemption so the DRA allocation state reflects
the preempted workload during the subsequent feasibility check, then restores
the original state afterward. Ensure buildAllocatedState and the lazy allocator
no longer include devices held only by the simulated-preempted workload.

In `@pkg/features/kube_features.go`:
- Line 692: Add TopologyAwareScheduling to the KueueDRADeviceFeasibility
dependencies in kube_features.go, and document TopologyAwareScheduling as a
required enablement prerequisite in keps/2941-DRA/README.md. Update both
affected sites: pkg/features/kube_features.go lines 692-692 and
keps/2941-DRA/README.md lines 433-436.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Advanced

Run ID: 37b31a94-3c60-4492-9acc-9462d46bdffa

📥 Commits

Reviewing files that changed from the base of the PR and between 7fc7d41 and 94934d0.

📒 Files selected for processing (16)

• cmd/kueue/main.go
• keps/2941-DRA/README.md
• pkg/cache/scheduler/simulator/dra_feasibility.go
• pkg/cache/scheduler/simulator/dra_feasibility_test.go
• pkg/cache/scheduler/simulator/types.go
• pkg/cache/scheduler/tas_flavor_snapshot.go
• pkg/cache/scheduler/tas_flavor_snapshot_test.go
• pkg/cache/scheduler/was/scheduling_simulator.go
• pkg/cache/scheduler/was/scheduling_simulator_stub.go
• pkg/cache/scheduler/was/scheduling_simulator_test.go
• pkg/features/kube_features.go
• pkg/util/testing/wrappers.go
• site/data/featuregates/versioned_feature_list.yaml
• test/compatibility_lifecycle/reference/versioned_feature_list.yaml
• test/integration/singlecluster/scheduler/was/suite_test.go
• test/integration/singlecluster/scheduler/was/was_test.go

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[tenzen-y]

on it.

[mimowo]

/lgtm
/approve
Thank you, it looks great 👍
/hold
in case @tenzen-y has extra comments

[kubernetes-prow]

LGTM label has been added.

Details

Git tree hash: 1e3bf9bd25d9b50e7be224ba3666cd19217f6563

[kubernetes-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: mimowo, sohankunkerkar

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[sohankunkerkar]

I just rebased to fix the conflicts.

[mimowo]

/lgtm
/unhold
Thank you 👍

[kubernetes-prow]

LGTM label has been added.

Details

Git tree hash: 3376bfb02492dd55aee9f24489df5c4a12e75a9a