Add semver comparison and CEL expressions support to Tolerations and NodeAffinity

[helayoty]

Enhancement Description

Currently, Kubernetes tolerations and NodeAffinity rules lack semantic versioning support. This feature will allow filtering based on semver ranges (e.g., >=v1.26.0). This enables clean support for firmware checks, Kubernetes version preferences, and other semver-based scheduling use cases.

Example

tolerations:
  - key: "node.kubernetes.io/kubelet-version"
    operator: "SemverGt"
    value: "v1.28.0"

This enhancement introduces semver-based toleration operators, SemverGt, SemverLt, SemverEq. and support semver comparison using CEL.

nodeAffinity:
  requiredDuringSchedulingIgnoredDuringExecution:
    nodeSelectorTerms:
      - matchExpressions:
          - key: "kubeletVersion"
            operator: "In"
            values: ["v1.28.0"]
  matchFields:
    - key: "metadata.labels['node.kubernetes.io/kubelet-version']"
      operator: Exists
  matchExpressionsWithCEL:
    - expression: semver_compare(metadata.labels['node.kubernetes.io/kubelet-version'], ">=1.27.0")

Background

Current KEP #5473 focuses on integer-only compliance for SLA/failure-probability for tolerations. However, semver handling is widely applicable:

• Comparing node kubelet versions (e.g., feature gating)
• Firmware version targeting for device scheduling
• Ensuring backward compatibility enforcement in heterogeneous clusters

Accommodating semver operators and CEL expression would make scheduling more flexible and future-proof.

/sig scheduling
/sig apps

• One-line enhancement description (can be used as a release note): Add Semantic Version Comparison and CEL expression Support to Tolerations and NodeAffinity
• Kubernetes Enhancement Proposal:
• Discussion Link: KEP-5471 Extended Toleration Operators for Threshold-Based Placement #5473 (comment)
• PRs by stage and milestone:
  • Alpha - v1.xx
    • KEP (k/enhancements) update PR(s):
    • Code (k/k) update PR(s):
    • Docs (k/website) update PR(s):

Please keep this description up to date. This will help the Enhancement Team to track the evolution of the enhancement efficiently.

[helayoty]

/sig scheduling
/sig apps
/stage alpha

[SergeyKanzhelev]

/cc

It will be quite a valuable feature for so many use cases!