Skip to content

[PodLevelResources] Update Downward API defaulting for resource limits #132605

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom
Open
wants to merge 1 commit into
base: master
Choose a base branch
from
Open

[PodLevelResources] Update Downward API defaulting for resource limits #132605

wants to merge 1 commit into from

Conversation

toVersus
Copy link
Contributor

What type of PR is this?

/kind bug

What this PR does / why we need it:

Using the Downward API's resourceFieldRef, you can inject values specified in resources.limits, such as CPU, memory, or ephemeral storage into environment variables. Currently, when container-level resource limits were not specified and the Downward API was used to set environment variables referencing them, the node's allocatable resources were used as the fallback. With the introduction of the Pod Level Resources feature, this behavior should be updated.

  • If container-level resource limits are not specified, the Downward API now uses the pod-level resource limits instead.
  • If neither container-level nor pod-level resource limits are specified, the behavior remains unchanged. It falls back to the node's allocatable resources.

Which issue(s) this PR is related to:

Fixes: #132603
KEP: kubernetes/enhancements#2837

Special notes for your reviewer:

Does this PR introduce a user-facing change?

The fallback behavior of the Downward API's `resourceFieldRef` field has been updated to account for pod-level resources: if container-level limits are not set, pod-level limits are now used before falling back to node allocatable resources.

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[KEP]: https://github.com/kubernetes/enhancements/issues/2837

@k8s-ci-robot k8s-ci-robot added release-note Denotes a PR that will be considered when it comes time to generate release notes. kind/bug Categorizes issue or PR as related to a bug. size/L Denotes a PR that changes 100-499 lines, ignoring generated files. cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. do-not-merge/needs-sig Indicates an issue or PR lacks a `sig/foo` label and requires one. needs-triage Indicates an issue or PR lacks a `triage/foo` label and requires one. labels Jun 29, 2025
@k8s-ci-robot
Copy link
Contributor

Hi @toVersus. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

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.

@k8s-ci-robot k8s-ci-robot added needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. needs-priority Indicates a PR lacks a `priority/foo` label and requires one. area/kubelet area/test kind/api-change Categorizes issue or PR as related to adding, removing, or otherwise changing an API sig/node Categorizes an issue or PR as relevant to SIG Node. sig/scheduling Categorizes an issue or PR as relevant to SIG Scheduling. labels Jun 29, 2025
@k8s-ci-robot k8s-ci-robot added sig/testing Categorizes an issue or PR as relevant to SIG Testing. and removed do-not-merge/needs-sig Indicates an issue or PR lacks a `sig/foo` label and requires one. labels Jun 29, 2025
@k8s-ci-robot
Copy link
Contributor

[APPROVALNOTIFIER] This PR is NOT APPROVED

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

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

Needs approval from an approver in each of these files:

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

@toVersus
Copy link
Contributor Author

/cc @ndixita

@k8s-ci-robot k8s-ci-robot requested a review from ndixita June 29, 2025 09:43
@k8s-triage-robot
Copy link

This PR may require API review.

If so, when the changes are ready, complete the pre-review checklist and request an API review.

Status of requested reviews is tracked in the API Review project.

ndixita
ndixita reviewed Jun 29, 2025
View reviewed changes
pkg/kubelet/kubelet_resources.go
@@ -42,13 +45,24 @@ func (kl *Kubelet) defaultPodLimitsForDownwardAPI(pod *v1.Pod, container *v1.Con
return nil, nil, fmt.Errorf("failed to find node object, expected a node")
}
allocatable := node.Status.Allocatable
if utilfeature.DefaultFeatureGate.Enabled(kubefeatures.PodLevelResources) && resourcehelper.IsPodLevelLimitsSet(pod) {
allocatable = allocatable.DeepCopy()
for _, resource := range []corev1.ResourceName{corev1.ResourceCPU, corev1.ResourceMemory, corev1.ResourceEphemeralStorage} {
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

nit - only cpu, memory and huge pages are supported at pod-level.

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Thanks! This slice contains resources supported by the Downward API, so I added a check to verify whether each resource is also supported by Pod Level Resources.

@ndixita
Copy link
Contributor

ndixita commented Jun 29, 2025

/triage accepted

@k8s-ci-robot k8s-ci-robot added triage/accepted Indicates an issue or PR is ready to be actively worked on. and removed needs-triage Indicates an issue or PR lacks a `triage/foo` label and requires one. labels Jun 29, 2025
@toVersus
[PodLevelResources] Update Downward API defaulting for resource limits
bedd1ef 
Currently, when container-level resource limits were not specified and
the Downward API was used to set environment variables referencing them,
the node's allocatable resources were used as the fallback.
With the introduction of the Pod Level Resources feature, this behavior
is updated: if container-level resource limits are not specified,
the Downward API now uses the pod-level resource limits instead.
If neither container-level nor pod-level resource limits are specified,
the behavior remains unchanged. It falls back to the node's allocatable
resources.

Signed-off-by: Tsubasa Nagasawa <[email protected]>
@toVersus toVersus force-pushed the feat/downward-api-plresources branch from adcfa0d to bedd1ef Compare June 30, 2025 00:33
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Reviewers

@ndixita ndixita ndixita left review comments

@haircommander haircommander Awaiting requested review from haircommander

@rphillips rphillips Awaiting requested review from rphillips

Assignees
No one assigned
Labels
area/kubelet area/test cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. kind/api-change Categorizes issue or PR as related to adding, removing, or otherwise changing an API kind/bug Categorizes issue or PR as related to a bug. needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. needs-priority Indicates a PR lacks a `priority/foo` label and requires one. release-note Denotes a PR that will be considered when it comes time to generate release notes. sig/node Categorizes an issue or PR as relevant to SIG Node. sig/scheduling Categorizes an issue or PR as relevant to SIG Scheduling. sig/testing Categorizes an issue or PR as relevant to SIG Testing. size/L Denotes a PR that changes 100-499 lines, ignoring generated files. triage/accepted Indicates an issue or PR is ready to be actively worked on.
Projects
SIG Node CI/Test Board
Status: Triage
SIG Node: code and documentation PRs
Status: Triage
Milestone
No milestone
Development

Successfully merging this pull request may close these issues.

[PodLevelResources] Update Downward API defaulting logic for resource.limits
4 participants
@toVersus @k8s-ci-robot @k8s-triage-robot @ndixita