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@LiangquanLi930 LiangquanLi930 commented Oct 15, 2025

✨ Implement autoscaling from zero by auto-populating AWSMachineTemplate capacity

What type of PR is this?
/kind feature

What this PR does / why we need it:
This PR implements the Cluster API autoscaling from zero proposal for CAPA by adding a controller that automatically populates AWSMachineTemplate.Status.Capacity with instance type information.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Special notes for your reviewer:

Checklist:

  • squashed commits
  • includes documentation
  • includes emoji in title
  • adds unit tests
  • adds or updates e2e tests

Release note:

Implement autoscaling from zero by auto-populating AWSMachineTemplate capacity

@k8s-ci-robot k8s-ci-robot added kind/feature Categorizes issue or PR as related to a new feature. do-not-merge/release-note-label-needed Indicates that a PR should not merge because it's missing one of the release note labels. cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. labels Oct 15, 2025
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[APPROVALNOTIFIER] This PR is NOT APPROVED

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@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. size/L Denotes a PR that changes 100-499 lines, ignoring generated files. labels Oct 15, 2025
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Hi @LiangquanLi930. Thanks for your PR.

I'm waiting for a kubernetes-sigs 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.

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@LiangquanLi930 LiangquanLi930 changed the title ✨ Implement autoscaling from zero by auto-populating AWSMachineTemplate capacity WIP ✨ Implement autoscaling from zero by auto-populating AWSMachineTemplate capacity Oct 15, 2025
@k8s-ci-robot k8s-ci-robot added the do-not-merge/work-in-progress Indicates that a PR should not merge because it is a work in progress. label Oct 15, 2025
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elmiko commented Oct 15, 2025

/ok-to-test

@k8s-ci-robot k8s-ci-robot added ok-to-test Indicates a non-member PR verified by an org member that is safe to test. and removed needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. labels Oct 15, 2025
@LiangquanLi930 LiangquanLi930 force-pushed the opt-in-autoscaling-from-zero branch 6 times, most recently from 50f8188 to f1ee365 Compare October 20, 2025 08:39
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/test pull-cluster-api-provider-aws-e2e-blocking

@LiangquanLi930 LiangquanLi930 force-pushed the opt-in-autoscaling-from-zero branch from f1ee365 to 3be8f4d Compare October 20, 2025 11:21
@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 Oct 20, 2025
@LiangquanLi930 LiangquanLi930 force-pushed the opt-in-autoscaling-from-zero branch 2 times, most recently from 01be987 to 915f55b Compare October 20, 2025 12:57
@k8s-ci-robot k8s-ci-robot added size/L Denotes a PR that changes 100-499 lines, ignoring generated files. and removed size/XL Denotes a PR that changes 500-999 lines, ignoring generated files. labels Oct 20, 2025
@LiangquanLi930 LiangquanLi930 force-pushed the opt-in-autoscaling-from-zero branch from 915f55b to b3850d1 Compare October 20, 2025 14:42
@k8s-ci-robot k8s-ci-robot added size/XL Denotes a PR that changes 500-999 lines, ignoring generated files. release-note Denotes a PR that will be considered when it comes time to generate release notes. and removed size/L Denotes a PR that changes 100-499 lines, ignoring generated files. do-not-merge/release-note-label-needed Indicates that a PR should not merge because it's missing one of the release note labels. labels Oct 20, 2025
@LiangquanLi930 LiangquanLi930 changed the title WIP ✨ Implement autoscaling from zero by auto-populating AWSMachineTemplate capacity Implement autoscaling from zero by auto-populating AWSMachineTemplate capacity Oct 20, 2025
@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 Oct 20, 2025
@LiangquanLi930 LiangquanLi930 changed the title Implement autoscaling from zero by auto-populating AWSMachineTemplate capacity ✨ Implement autoscaling from zero by auto-populating AWSMachineTemplate capacity Oct 20, 2025
@LiangquanLi930 LiangquanLi930 changed the title ✨ Implement autoscaling from zero by auto-populating AWSMachineTemplate capacity ✨ feat: Implement autoscaling from zero by auto-populating AWSMachineTemplate capacity Oct 20, 2025
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elmiko commented Oct 21, 2025

/assign

Comment on lines +71 to +73
if len(awsMachineTemplate.Status.Capacity) > 0 {
return ctrl.Result{}, nil
}
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@chrischdi chrischdi Oct 22, 2025

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What if the capacity is not correct? Or is the .spec.template.spec.instanceType immutable?

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IIUC, spec.template.spec.instanceType is immutable:

if !topology.ShouldSkipImmutabilityChecks(req, newAWSMachineTemplate) && !cmp.Equal(newAWSMachineTemplate.Spec, oldAWSMachineTemplate.Spec) {
if oldAWSMachineTemplate.Spec.Template.Spec.InstanceMetadataOptions == nil {
oldAWSMachineTemplate.Spec.Template.Spec.InstanceMetadataOptions = newAWSMachineTemplate.Spec.Template.Spec.InstanceMetadataOptions
}
if !cmp.Equal(newAWSMachineTemplate.Spec.Template.Spec, oldAWSMachineTemplate.Spec.Template.Spec) {
allErrs = append(allErrs,
field.Invalid(field.NewPath("spec", "template", "spec"), newAWSMachineTemplate, "AWSMachineTemplate.Spec is immutable"),
)
}
}

The webhook enforces that spec.template.spec cannot be changed after creation, except when topology.ShouldSkipImmutabilityChecks() returns true (which is only for ClusterClass topology patches).

Therefore, I think the current early-return logic is correct.

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Sounds good

clusterv1 "sigs.k8s.io/cluster-api/api/v1beta1"
)

func TestAWSMachineTemplateReconciler(t *testing.T) {
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Could there also be a unit test which expects actual correct values instead of just checking "capacity" is set?

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+1

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elmiko commented Oct 22, 2025

nodeInfo would be nice to have, architecture should be relatively easy to determine but i'm not sure about operating system.

that said, nodeInfo is an extension to the original opt-in scale from zero, if arch and o/s are not present the autoscaler will still be able to scale based on resources alone.

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/test pull-cluster-api-provider-aws-e2e

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in general this is looking good to me, i tend to agree with Christian's questions.

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/test pull-cluster-api-provider-aws-e2e

@LiangquanLi930 LiangquanLi930 force-pushed the opt-in-autoscaling-from-zero branch from 679c53a to 3208d4c Compare October 23, 2025 09:51
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/test pull-cluster-api-provider-aws-e2e

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@LiangquanLi930: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name Commit Details Required Rerun command
pull-cluster-api-provider-aws-e2e 3208d4c link false /test pull-cluster-api-provider-aws-e2e

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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. I understand the commands that are listed here.

@LiangquanLi930 LiangquanLi930 force-pushed the opt-in-autoscaling-from-zero branch from 3208d4c to 5abc575 Compare October 23, 2025 13:46
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