Consistent Reads from Cache

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

#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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This bot triages issues and PRs according to the following rules:

• After 90d of inactivity, lifecycle/stale is applied
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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