DualStack apiserver support

[danwinship]

Dual-stack apiserver support

• One-line enhancement description (can be used as a release note): Make the apiserver service dual-stack in dual-stack clusters
• Kubernetes Enhancement Proposal: https://github.com/kubernetes/enhancements/tree/master/keps/sig-network/2438-dual-stack-apiserver
• Discussion Link: Discussed in sig-net on Jan 21, then a bit on slack (https://kubernetes.slack.com/archives/CGF3A900N/p1611328345018100, including a second thread off a later comment)
• Primary contact (assignee): @danwinship
• Responsible SIGs: sig-network, sig-apimachinery
• Enhancement target (which target equals to which milestone):
  • Alpha release target (x.y): 1.23(?)
  • Beta release target (x.y): 1.25?
  • Stable release target (x.y): 1.26?
• Alpha
  • KEP (k/enhancements) update PR(s):
  • Code (k/k) update PR(s):
  • Docs (k/website) update PR(s): WIP dual-stack apiserver documentation website#32034

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

[danwinship]

/sig network
/sig api-machinery

[fejta-bot]

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[flokli]

This is still very much desired ;-)

[flokli]

/remove-lifecycle stale

[salaxander]

/milestone v1.23

[salaxander]

/stage beta

[salaxander]

Hi @danwinship! 1.23 Enhancements team here. Just checking in as we approach enhancements freeze at 11:59pm PST on Thursday 09/09. Here's where this enhancement currently stands:

• Updated KEP file using the latest template has been merged into the k/enhancements repo.
• KEP status is marked as implementable
• KEP has a test plan section filled out.
• KEP has up to date graduation criteria.
• KEP has a production readiness review that has been completed and merged into k/enhancements.

For this one, looks like we'll need the kep.yaml updated to reflect the current stage and latest milestone. It also looks like you'll still need to complete a PRR.

Thanks!

[danwinship]

@salaxander sorry, the initial description hadn't been updated in a while. This did not go alpha in 1.22 and thus is not scheduled to go beta in 1.23 (but should hopefully be alpha, and I think we are good there, because you don't need a completed PRR to go to alpha)

[salaxander]

@danwinship sounds good! Then we're all good once the KEP updated merges

[johnbelamaric]

If you want to hit 1.23 you need a PRR soon. Should be pretty simple.

[johnbelamaric]

/stage alpha

[salaxander]

Hi, 1.23 Enhancements Lead here 👋. With enhancements freeze now in effect, this enhancement has not met the criteria for the freeze and has been removed from the milestone.

As a reminder, the criteria for enhancements freeze is:

• KEP is merged into k/enhancements repo with up to date latest milestone and stage.
• KEP status is marked as implementable.
• KEP has a test plan section filled out.
• KEP has up to date graduation criteria.
• KEP has a production readiness review for the correct stage that has been completed and merged into k/enhancements.

Feel free to file an exception to add this back to the release. If you plan to do so, please file this as early as possible.

Thanks!
/milestone clear

[thockin]

No progress for 1.26

[k8s-triage-robot]

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[flokli]

/remove-lifecycle stale

[sftim]

(from the KEP)

Another possibility is that instead of cooperatively maintaining a
single EndpointSlice (or pair of EndpointSlices), each apiserver would
write out its own slice(s) containing only its own IP(s). Clients
would then have to aggregate all of the slices together to get the
full list of active IPs.

I like the idea of an EndpointSlice per API server and recommending that as the discovery mechanism. There can still be a reconciler making a best effort to update a single-stack Endpoints based on those EndpointSlices; legacy support is important.

The individual EndpointSlices then each have their own metadata, which allows things like (say) annotating one of the EndpointSlices to record self-observations, or labelling the endpoint slice with API server identity (cf https://kubernetes.io/docs/concepts/architecture/leases/#api-server-identity). It shouldn't be a scaling issue as few clusters have more than 9 API servers.

[sftim]

Another benefit, potentially:

If I (mis)configure two API servers to have the same IPv4 address, a mechanism with a single EndpointSlice per address family leads both API servers to conclude that their identity is reconciled. With an EndpointSlice per API server, the conflict allows all API servers in the cluster to spot the clash and report this via metrics.

[k8s-triage-robot]

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[PKizzle]

/remove-lifecycle stale

[thockin]

Anyone touching this in 1.29? @danwinship

[k8s-triage-robot]

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[flokli]

/remove-lifecycle stale

[k8s-triage-robot]

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[flokli]

/remove-lifecycle stale

[k8s-triage-robot]

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

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[flokli]

/remove-lifecycle stale

[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
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/lifecycle stale

[flokli]

/remove-lifecycle stale