sig-cl/kubeadm: Use etcd's learner mode

[neolit123]

Enhancement Description

• One-line enhancement description (can be used as a release note): use etcd's learner mode for joining etcd members to the etcd cluster managed by kubeadm
• Kubernetes Enhancement Proposal: https://github.com/kubernetes/enhancements/blob/master/keps/sig-cluster-lifecycle/kubeadm/3614-etcd-learner-mode/README.md
• Discussion Link:
  • https://hackmd.io/XZHxeO21T-GDgRhjtVwlGQ
  • RFE: use learner mode for joining etcd members kubeadm#1793
• Primary contact (assignee): @neolit123 @pacoxu
• Responsible SIGs: sig-cluster-lifecycle
• Enhancement target (which target equals to which milestone):
  • Alpha release target (x.y): 1.27
  • Beta release target (x.y): 1.29
  • Stable release target (x.y): 1.32
• Alpha
  • KEP (k/enhancements) update PR(s): sig-cl/kubeadm: add provisional KEP for etcd learner mode #3615
  • Code (k/k) update PR(s): kubeadm: enable etcd's learner mode when joining etcd members kubernetes#113318 and kubeadm: fix etcd learner join kubernetes#115038
  • Docs (k/website) update PR(s): kubeadm: update feature gates and add removed FGs website#42771
• Beta
  • KEP (k/enhancements) update PR(s): update etcd learner mode status of kubeadm implementation #4172
  • Code (k/k) update PR(s): kubeadm: promote EtcdLearnerMode to beta kubernetes#120228
  • Docs (k/website) update(s): kubeadm: EtcdLearnerMode is beta in v1.29 website#42801; add a new blog for etcd learner mode usage in kubeadm join website#43095
• Stable
  • KEP (k/enhancements) update PR(s):
  • Code (k/k) update PR(s): [1.32]kubeadm: promote etcd learner mode to GA  kubernetes#126374
  • Docs (k/website) update(s):

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

[k8s-triage-robot]

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/lifecycle stale

[pacoxu]

The alpha implemented PR was merged: kubernetes/kubernetes#113318.

• a fix for the implementation is in process kubeadm: fix etcd learner join kubernetes#115038

E2E test will be added by kubernetes/kubeadm#2807 and kubernetes/test-infra#28574.

I think this will be alpha in v1.27. The KEP was merged in v1.26 release cycle #3615.
A KEP update is needed. I will submit a PR ASAP.

We plan to move this to alpha in v1.27.

[k8s-triage-robot]

The Kubernetes project currently lacks enough contributors to adequately respond to all issues.

This bot triages un-triaged issues according to the following rules:

• After 90d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
• After 30d of inactivity since lifecycle/rotten was applied, the issue is closed

You can:

• Mark this issue as fresh with /remove-lifecycle stale
• Close this issue with /close
• Offer to help out with Issue Triage

Please send feedback to sig-contributor-experience at kubernetes/community.

/lifecycle stale

[pacoxu]

/remove-lifecycle stale

[pacoxu]

I prefer to wait for more feedback in v1.28 release cycle and promote it to beta in a later release(1.29 or later).

• testgrid: https://testgrid.k8s.io/sig-cluster-lifecycle-kubeadm#kubeadm-kinder-learner-mode-latest