DRA: Constraints with CEL

[geetasg]

Enhancement Description

DRA supports specifying constraints for device allocation. Currently, it supports the MatchAttribute constraint, which ensures that all selected devices have a specific attribute and that the type and value of this attribute are consistent across these devices. This enhancement proposal aims to add a new MatchExpression constraint that will allow devices to be evaluated against a CEL expression. For example - consider an accelerator architecture where connected devices have sequential identifiers. A MatchExpression constraint can help select a subset of these connected devices. This feature was previously identified as a potential future extension in the original KEP for structured parameters, and this proposal seeks to implement that extension.
Ref: - https://github.com/kubernetes/enhancements/blame/master/keps/sig-node/4381-dra-structured-parameters/README.md#L1597

• One-line enhancement description (can be used as a release note): Provide a mechanism which compares different devices and returns true if they qualify as an optimal set.
• Kubernetes Enhancement Proposal: TBD
• Discussion Link: Discussed in community meeting on 4/15/2025
• Primary contact (assignee): geetasg
• Responsible SIGs: Scheduling
• Enhancement target (which target equals to which milestone):
  • Alpha release target (x.y): 1.34
  • Beta release target (x.y):
  • Stable release target (x.y):
• Alpha
  • KEP (k/enhancements) update PR(s): [KEP-5254] DRA: Constraints with CEL #5391
  • 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.

[geetasg]

cc @pohly @dims

[k8s-ci-robot]

@geetasg: The label(s) wg/, wg/wg-device-management cannot be applied, because the repository doesn't have them.

In response to this:

/wg wg-device-management

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[pohly]

/wg device-management
/title DRA: MatchExpression

This is valid and consistent with the original design. I can see use cases for it which aren't possible with the existing MatchAttributes. Let's discuss a bit more in the #wg-device-management Slack channel before creating the KEP.

[geetasg]

Capturing api suggestion from @pohly and @johnbelamaric (discussion over slack)

constraints:
- cel:
    expression: <something involving devices>

[pohly]

The entire feature then needs to be renamed. How about DRA: CEL Constraints with DRACELConstraints as feature gate?

Alternative: "DRA: Constraints with CEL", DRAConstraintsWithCEL - more verbose, but avoids direct concatenation of "DRA" and "CEL".

[pohly]

/assign @geetasg

[johnbelamaric]

/retitle DRA: Constraints with CEL

yes, that's good