[Beta: 1.31] Consistent Reads from Cache

[shekhar-rajak]

Enhancement Description

• One-line enhancement description : Consistent Reads from Cache
• Kubernetes Enhancement Proposal:

Kubernetes Get and List requests are guaranteed to be "consistent reads" if the
resourceVersion parameter is not provided. Consistent reads are served from
etcd using a "quorum read".

But often the watch cache contains sufficiently up-to-date data to serve the
read request, and could serve it far more efficiently.

This KEP proposes a mechanism to serve most reads from the watch cache
while still providing the same consistency guarantees as serving the
read from etcd.

• Discussion Link:
• KEP link: https://github.com/kubernetes/enhancements/blob/master/keps/sig-api-machinery/2340-Consistent-reads-from-cache/README.md
• Primary contact (assignee): @serathius
• Responsible SIGs: sig-api-machinery
• Enhancement target (which target equals to which milestone):
  • Alpha 1.28
    • KEP (k/enhancements) update PR(s):
      • Revive 2340 Consistent reads from cache KEP #4047
    • Code (k/k) update PR(s): Implement Alpha state for KEP #2340 kubernetes#118508
    • Docs (k/website) update PR(s): Document Consistent Reads from Cache website#42083
    • Scalability tests: Test consistent list from cache test-infra#30094
  • Beta 1.31
    • KEP (k/enhancements) update PR(s):
      • Move KEP 2340 to Beta #4134
    • Code (k/k) update PR(s):
      • Improve progress notify to have more correct and predictable period of triggering kubernetes#125115
      • Feat: warn user if etcd version is not supported for RequestWatchProgress feature. kubernetes#124612 Implement checking etcd version to warn about deprecated etcd versions kubernetes#123264)
      • Add FeatureSupportChecker for etcd storage kubernetes#124483
      • Move ConsistentListFromCache to Beta default kubernetes#123513
      • consistent-list-from-cache tests are broken perf-tests#2540
      • Implement apiserver_watch_cache_read_wait metric kubernetes#123185
      • Implement per-request watch cache opt-out kubernetes#123187
      • Implement checking etcd version to warn about deprecated etcd versions kubernetes#123192
      • Move ConsistentListFromCache to Beta default kubernetes#123513

All tasks done for beta

[shekhar-rajak]

#2331 created for migrating the old keps into new template.

[lasomethingsomething]

/sig api-machinery

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@k8s-triage-robot: Closing this issue.

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[serathius]

Reviving the KEP as agreed on SIG-Apimachinery meeting May 31st 2023. https://youtu.be/sueYXW89ZHg
/assign

PR #4047 to move KEP to implementable

[serathius]

/stage alpha

[serathius]

/milestone v1.28

[jpbetz]

/lead opt-in

[Atharva-Shinde]

Hello @shekhar-rajak @serathius 👋, Enhancements team here.

Just checking in as we approach Enhancements freeze on Thursday, 16th June 2023.

Looks like this enhancement is targeting for stage alpha for v1.28

Here's where this enhancement currently stands:

• KEP readme using the latest template has been merged into the k/enhancements repo.
• KEP status is marked as implementable for latest-milestone:v1.28
• KEP readme has an updated detailed test plan section filled out
• KEP readme has up to date graduation criteria
• KEP has a production readiness review that has been completed and merged into k/enhancements.

There are some nits remaining to be addressed:

• Update kep.yaml with latest last update date.
• Add acknowledgement under the Test Plan section.

I won't decline this KEP for enhancements freeze because of these minor changes but would be great to get a PR ready addressing them.

The status of this enhancement is marked as tracked. Please keep the issue description up-to-date with appropriate stages as well. Thank you :)

[serathius]

Don't understand the unmarked points.

KEP readme using the latest template has been merged into the k/enhancements repo.
KEP readme has an updated detailed test plan section filled out

Tests follows the latest template (maybe roughly) and uses a detailed test plan. Please provide criteria that you used to decide that they are not.

[Atharva-Shinde]

Hey @serathius , the second unmarked point is a subset of the first unmarked point.
As mentioned in my comment above, there is an acknowledgement at the start of the Test Plan section quoting:

[ ] I/we understand the owners of the involved components may require updates to
existing tests to make this code solid enough prior to committing the changes necessary
to implement this enhancement.

which this KEP currently doesn't have and we need that to be included so that the KEP is in compliance with the latest KEP readme template.

[serathius]

Makes sense, suggestion for future. Separate questionnaire to KEP authors (also applies to PRR) from KEPs design document into separate file. Having agreements in the middle of the design makes it less readable, doesn't contribute to overall design and also cannot be automatically validated via ./hack/verify-kep.sh.

[serathius]

Hey @dipesh-rawat, thanks for reaching out.
All the coding work has been completed for the Beta milestone.

The only work left is documentation and blogpost.

[dipesh-rawat]

@serathius Thanks for the confirmation (here) that the coding work is complete.

With all the implementation(code related) PRs merged as per the issue description:

• Improve progress notify to have more correct and predictable period of triggering kubernetes#125115
• Feat: warn user if etcd version is not supported for RequestWatchProgress feature. kubernetes#124612
• Add FeatureSupportChecker for etcd storage kubernetes#124483
• Move ConsistentListFromCache to Beta default kubernetes#123513

This enhancement is now marked as tracked for code freeze for the 1.31 Code Freeze!

[sreeram-venkitesh]

@serathius Going through open PRs in k/k, I could find kubernetes/kubernetes#125605 which is related to this KEP. Can you please confirm if this PR is part of the implementation for this KEP? The only file change seems to be in a test file. If so, please make sure to get it merged before the test freeze deadline (01:00 UTC Wednesday 31st July 2024 / 19:00 PDT Tuesday 30th July 2024).

[serathius]

No, this PR is not related, however we were kicked out of Beta with kubernetes/kubernetes#126139 :(

Working on a fix in kubernetes/kubernetes#126264, but due to limited capacity of reviews might not get in before code freeze.

[sreeram-venkitesh]

Ohh :(

So with kubernetes/kubernetes#126139 merged, the feature gate is flipped back although all the code was merged, correct?

[serathius]

So with kubernetes/kubernetes#126139 merged, the feature gate is flipped back although all the code was merged, correct?

Yes

[sreeram-venkitesh]

/milestone clear

[sreeram-venkitesh]

/milestone v1.31

[tjons]

Hi, enhancements lead here - I inadvertently added this to the 1.32 tracking board 😀

/remove-label lead-opted-in

[k8s-triage-robot]

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[k8s-triage-robot]

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

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

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[serathius]

/remove-lifecycle rotten