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Add APIs for configuring fair sharing #2070

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merged 10 commits into from
May 8, 2024

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alculquicondor
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@alculquicondor alculquicondor commented Apr 25, 2024

What type of PR is this?

/kind feature

What this PR does / why we need it:

Add APIs for fair sharing:

  • In KueueConfiguration, a new FairSharing struct to enable the feature and configure strategies.
  • In ClusterQueueSpec, a new FairSharing struct containing the weight.

Which issue(s) this PR fixes:

Fixes #1714

Special notes for your reviewer:

At this point, I'm looking for feedback on the types and field documentation.

Does this PR introduce a user-facing change?

Add fair sharing when borrowing unused resources from other ClusterQueues in a cohort.

Fair sharing is based on DRF for usage above nominal quotas.
When fair sharing is enabled, Kueue prefers to admit workloads from ClusterQueues with the lowest share first.
Administrators can enable and configure fair sharing preemption using a combination of two policies: `LessThanOrEqualtoFinalShare`, `LessThanInitialShare`.

You can define a fair sharing `weight` for ClusterQueues. The weight determines how much of the unused resources each ClusterQueue can take in comparison to others.

@k8s-ci-robot k8s-ci-robot added release-note Denotes a PR that will be considered when it comes time to generate release notes. do-not-merge/work-in-progress Indicates that a PR should not merge because it is a work in progress. kind/feature Categorizes issue or PR as related to a new feature. labels Apr 25, 2024
@k8s-ci-robot k8s-ci-robot added cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. approved Indicates a PR has been approved by an approver from all required OWNERS files. size/L Denotes a PR that changes 100-499 lines, ignoring generated files. labels Apr 25, 2024
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cc @mwielgus @tenzen-y

apis/kueue/v1beta1/clusterqueue_types.go Show resolved Hide resolved
apis/config/v1beta1/configuration_types.go Outdated Show resolved Hide resolved
apis/config/v1beta1/configuration_types.go Outdated Show resolved Hide resolved
apis/config/v1beta1/configuration_types.go Outdated Show resolved Hide resolved
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@alculquicondor alculquicondor force-pushed the fair-sharing-api branch 4 times, most recently from cdb3926 to 87453cf Compare April 26, 2024 18:57
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I left a comment for a nit.

pkg/config/validation.go Outdated Show resolved Hide resolved
@k8s-ci-robot k8s-ci-robot added size/XL Denotes a PR that changes 500-999 lines, ignoring generated files. and removed size/L Denotes a PR that changes 100-499 lines, ignoring generated files. labels May 3, 2024
@alculquicondor alculquicondor changed the title WIP: Add APIs for configuring fair sharing Add APIs for configuring fair sharing May 3, 2024
@k8s-ci-robot k8s-ci-robot removed the do-not-merge/work-in-progress Indicates that a PR should not merge because it is a work in progress. label May 3, 2024
@alculquicondor alculquicondor force-pushed the fair-sharing-api branch 2 times, most recently from 9cb7292 to fc94535 Compare May 3, 2024 18:02
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This is now ready for review 😄

/assign @tenzen-y @mwielgus

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Totally, lgtm
I left a few comments.
By the way, it seems that the fairSharing feature overlaps borrowWithinCohort at some points. So, in the v1 API, we might be able to consolidate both APIs into a single one or provide a comprehensive feature somehow.

pkg/cache/clusterqueue.go Outdated Show resolved Hide resolved
pkg/scheduler/preemption/preemption.go Outdated Show resolved Hide resolved
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By the way, it seems that the fairSharing feature overlaps borrowWithinCohort at some points. So, in the v1 API, we might be able to consolidate both APIs into a single one or provide a comprehensive feature somehow.

Did you mean that borrowWithinCohort can be replaced by using weight: 0?

If so, I agree. I would like to completely remove borrowWithinCohort once we go to v1, unless we hear some opposing feedback.

@k8s-ci-robot k8s-ci-robot added the needs-rebase Indicates a PR cannot be merged because it has merge conflicts with HEAD. label May 6, 2024
Change-Id: I74b24ba8715290753c0bd9b966a109b5b01078b4
Change-Id: If347eabdb17af643d46a1e4ad78b79e73c424011
Change-Id: I6938d83399c55fecf952a570e2e431ad4ab479b2
Change-Id: I8b49d21f0b0e7a7d2607d9589ba49a4a914cd2aa
Change-Id: I68ba0c546ce27d9e6565a30584aacd67fd318ede
Change-Id: I375166b8c7fdc300eeb43ede25fbcbe73298c7a2
Change-Id: I4d56c73f4a949fa5c2b2053fd83a7161553755b0
@k8s-ci-robot k8s-ci-robot removed the needs-rebase Indicates a PR cannot be merged because it has merge conflicts with HEAD. label May 7, 2024
// This strategy doesn't depend on the share usage of the workload being preempted.
// As a result, the strategy chooses to preempt workloads with the lowest priority and
// newest start time first.
// The default strategy is ["LessThanOrEqualToFinalShare"].
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As per offline discussions we consider the two combinations as most likely in use:

  1. [LessThanOrEqualToFinalShare, LessThanInitialShare] and
  2. [LessThanInitialShare]

So, I would suggest setting the default to one of the configurations.

I would vote for the [LessThanOrEqualToFinalShare, LessThanInitialShare] since it matches the KEP.

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Done

}
if s[0] == config.LessThanInitialShare {
result[0] = lessThanInitialShare
// This rule is a superset of the other rule, no need to check other strategies.
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Since we go for the "mathematical" approach, I would suggest to be precise, and don't make the assumption that Rule B is a superset of Rule A (since unlikely scenarios may happen).

allErrs = append(allErrs, field.Invalid(fsPreemptionStrategiesPath, fs.PreemptionStrategies, "Must be empty when fair sharing is disabled"))
}
strategies := sets.New[configapi.PreemptionStrategy]()
validStrategies := []configapi.PreemptionStrategy{configapi.LessThanInitialShare, configapi.LessThanOrEqualToFinalShare}
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I think we should either validate against non-supported configurations or support them. I'm leaning towards validation, because it will keep the code simpler. IIUC this is the only non-supported option for now: [LessThanInitialShare, LessThanOrEqualToFinalShare] .

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Changed validation to have an explicit list of supported combinations.

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borrowWithinCohort once we go to v1, unless we

But why, do we have similar capacity covered this?

Yes, the biggest motivation to have borrowWithinCohort was to allow certain ClusterQueues to always be preempted whenever some other CQ needs the resources.

And this can be easily achieved when enabling fair sharing, by setting the weight on these "preemptible" CQs to zero.

Change-Id: I6893b7854656601e80f157b60caea27e27dfe4ea
Change-Id: I6379c4304cfb45a08940d57a24b79c6b1564ccca
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@tenzen-y anything to add?

@@ -50,3 +50,6 @@ integrations:
# - key: kubernetes.io/metadata.name
# operator: NotIn
# values: [ kube-system, kueue-system ]
# fairSharing:
# enable: true
# preemptionStrategies: [LessThanOrEqualToFinalShare]
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nit: Maybe align this with the current default?

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Done

Comment on lines 211 to 213
if !fs.Enable && len(fs.PreemptionStrategies) != 0 {
allErrs = append(allErrs, field.Invalid(fsPreemptionStrategiesPath, fs.PreemptionStrategies, "Must be empty when fair sharing is disabled"))
}
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Do we need it? I guess it can be handy to keep th configuration when temporarily disabling the feature.
Similarly as for waitForPodsReady.

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If there are no drawbacks (similar to additional computation, and potentially bugs in preemptor), I would prefer to apply the @mimowo proposal here.

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SG. Done

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mimowo commented May 8, 2024

I did another pass for fair sharing, lgtm, just the two nit-like comments

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LGTM
Thank you!

apis/config/v1beta1/configuration_types.go Show resolved Hide resolved
Comment on lines 211 to 213
if !fs.Enable && len(fs.PreemptionStrategies) != 0 {
allErrs = append(allErrs, field.Invalid(fsPreemptionStrategiesPath, fs.PreemptionStrategies, "Must be empty when fair sharing is disabled"))
}
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If there are no drawbacks (similar to additional computation, and potentially bugs in preemptor), I would prefer to apply the @mimowo proposal here.

Change-Id: I1ec9229cb866d31ece5046741ac7686157639758
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Hugely LGTM!
The implementation of the FairSharing feature inspired by Dominant Resource Fairness was not a really easy journey! Awsome 🎉

/lgtm
/approve

@k8s-ci-robot k8s-ci-robot added the lgtm "Looks good to me", indicates that a PR is ready to be merged. label May 8, 2024
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LGTM label has been added.

Git tree hash: 07fccade5bb30526c1bae6d4b147b6d21d43dcf8

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: alculquicondor, tenzen-y

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@k8s-ci-robot k8s-ci-robot merged commit 54d1c01 into kubernetes-sigs:main May 8, 2024
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@k8s-ci-robot k8s-ci-robot added this to the v0.7 milestone May 8, 2024
kannon92 pushed a commit to openshift-kannon92/kubernetes-sigs-kueue that referenced this pull request Nov 19, 2024
* Add APIs for configuring fair sharing

Change-Id: I74b24ba8715290753c0bd9b966a109b5b01078b4

* Validation and defaulting for fair sharing

Change-Id: If347eabdb17af643d46a1e4ad78b79e73c424011

* Implement multiple fair strategies

Change-Id: I6938d83399c55fecf952a570e2e431ad4ab479b2

* Implement fair sharing weight

Change-Id: I8b49d21f0b0e7a7d2607d9589ba49a4a914cd2aa

* Fix flaky integration

Change-Id: I68ba0c546ce27d9e6565a30584aacd67fd318ede

* review

Change-Id: I375166b8c7fdc300eeb43ede25fbcbe73298c7a2

* Update documentation for strategies

Change-Id: I4d56c73f4a949fa5c2b2053fd83a7161553755b0

* Change default configuration to match KEP

Change-Id: I6893b7854656601e80f157b60caea27e27dfe4ea

* Disable fair sharing by default

Change-Id: I6379c4304cfb45a08940d57a24b79c6b1564ccca

* Relax validation

Change-Id: I1ec9229cb866d31ece5046741ac7686157639758
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Support for fair sharing of unused resources
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