From 1b39aa7cd7495dae041421e97f1eb37aa7df3830 Mon Sep 17 00:00:00 2001
From: Jan Safranek <jsafrane@redhat.com>
Date: Fri, 20 Jan 2023 17:39:43 +0100
Subject: [PATCH] Add draft of volume reconstruction KEP

---
 .../3756-volume-reconstruction/README.md      | 905 ++++++++++++++++++
 .../3756-volume-reconstruction/kep.yaml       |  44 +
 2 files changed, 949 insertions(+)
 create mode 100644 keps/sig-storage/3756-volume-reconstruction/README.md
 create mode 100644 keps/sig-storage/3756-volume-reconstruction/kep.yaml

diff --git a/keps/sig-storage/3756-volume-reconstruction/README.md b/keps/sig-storage/3756-volume-reconstruction/README.md
new file mode 100644
index 000000000000..ed6a71eff306
--- /dev/null
+++ b/keps/sig-storage/3756-volume-reconstruction/README.md
@@ -0,0 +1,905 @@
+<!--
+**Note:** When your KEP is complete, all of these comment blocks should be removed.
+
+To get started with this template:
+
+- [x] **Pick a hosting SIG.**
+  Make sure that the problem space is something the SIG is interested in taking
+  up. KEPs should not be checked in without a sponsoring SIG.
+- [x] **Create an issue in kubernetes/enhancements**
+  When filing an enhancement tracking issue, please make sure to complete all
+  fields in that template. One of the fields asks for a link to the KEP. You
+  can leave that blank until this KEP is filed, and then go back to the
+  enhancement and add the link.
+- [x] **Make a copy of this template directory.**
+  Copy this template into the owning SIG's directory and name it
+  `NNNN-short-descriptive-title`, where `NNNN` is the issue number (with no
+  leading-zero padding) assigned to your enhancement above.
+- [ ] **Fill out as much of the kep.yaml file as you can.**
+  At minimum, you should fill in the "Title", "Authors", "Owning-sig",
+  "Status", and date-related fields.
+- [ ] **Fill out this file as best you can.**
+  At minimum, you should fill in the "Summary" and "Motivation" sections.
+  These should be easy if you've preflighted the idea of the KEP with the
+  appropriate SIG(s).
+- [ ] **Create a PR for this KEP.**
+  Assign it to people in the SIG who are sponsoring this process.
+- [ ] **Merge early and iterate.**
+  Avoid getting hung up on specific details and instead aim to get the goals of
+  the KEP clarified and merged quickly. The best way to do this is to just
+  start with the high-level sections and fill out details incrementally in
+  subsequent PRs.
+
+Just because a KEP is merged does not mean it is complete or approved. Any KEP
+marked as `provisional` is a working document and subject to change. You can
+denote sections that are under active debate as follows:
+
+```
+<<[UNRESOLVED optional short context or usernames ]>>
+Stuff that is being argued.
+<<[/UNRESOLVED]>>
+```
+
+When editing KEPS, aim for tightly-scoped, single-topic PRs to keep discussions
+focused. If you disagree with what is already in a document, open a new PR
+with suggested changes.
+
+One KEP corresponds to one "feature" or "enhancement" for its whole lifecycle.
+You do not need a new KEP to move from beta to GA, for example. If
+new details emerge that belong in the KEP, edit the KEP. Once a feature has become
+"implemented", major changes should get new KEPs.
+
+The canonical place for the latest set of instructions (and the likely source
+of this file) is [here](/keps/NNNN-kep-template/README.md).
+
+**Note:** Any PRs to move a KEP to `implementable`, or significant changes once
+it is marked `implementable`, must be approved by each of the KEP approvers.
+If none of those approvers are still appropriate, then changes to that list
+should be approved by the remaining approvers and/or the owning SIG (or
+SIG Architecture for cross-cutting KEPs).
+-->
+# KEP-3756: Robust VolumeManager reconstruction after kubelet restart
+<!-- toc -->
+- [Release Signoff Checklist](#release-signoff-checklist)
+- [Summary](#summary)
+- [Motivation](#motivation)
+  - [Goals](#goals)
+  - [Non-Goals](#non-goals)
+- [Proposal](#proposal)
+  - [User Stories (Optional)](#user-stories-optional)
+    - [Story 1](#story-1)
+    - [Story 2](#story-2)
+  - [Notes/Constraints/Caveats (Optional)](#notesconstraintscaveats-optional)
+  - [Risks and Mitigations](#risks-and-mitigations)
+- [Design Details](#design-details)
+  - [Test Plan](#test-plan)
+      - [Prerequisite testing updates](#prerequisite-testing-updates)
+      - [Unit tests](#unit-tests)
+      - [Integration tests](#integration-tests)
+      - [e2e tests](#e2e-tests)
+  - [Graduation Criteria](#graduation-criteria)
+  - [Upgrade / Downgrade Strategy](#upgrade--downgrade-strategy)
+  - [Version Skew Strategy](#version-skew-strategy)
+- [Production Readiness Review Questionnaire](#production-readiness-review-questionnaire)
+  - [Feature Enablement and Rollback](#feature-enablement-and-rollback)
+  - [Rollout, Upgrade and Rollback Planning](#rollout-upgrade-and-rollback-planning)
+  - [Monitoring Requirements](#monitoring-requirements)
+  - [Dependencies](#dependencies)
+  - [Scalability](#scalability)
+  - [Troubleshooting](#troubleshooting)
+- [Implementation History](#implementation-history)
+- [Drawbacks](#drawbacks)
+- [Alternatives](#alternatives)
+- [Infrastructure Needed (Optional)](#infrastructure-needed-optional)
+<!-- /toc -->
+
+## Release Signoff Checklist
+
+Items marked with (R) are required *prior to targeting to a milestone / release*.
+
+- [ ] (R) Enhancement issue in release milestone, which links to KEP dir in [kubernetes/enhancements] (not the initial KEP PR)
+- [ ] (R) KEP approvers have approved the KEP status as `implementable`
+- [ ] (R) Design details are appropriately documented
+- [ ] (R) Test plan is in place, giving consideration to SIG Architecture and SIG Testing input (including test refactors)
+  - [ ] e2e Tests for all Beta API Operations (endpoints)
+  - [ ] (R) Ensure GA e2e tests meet requirements for [Conformance Tests](https://github.com/kubernetes/community/blob/master/contributors/devel/sig-architecture/conformance-tests.md) 
+  - [ ] (R) Minimum Two Week Window for GA e2e tests to prove flake free
+- [ ] (R) Graduation criteria is in place
+  - [ ] (R) [all GA Endpoints](https://github.com/kubernetes/community/pull/1806) must be hit by [Conformance Tests](https://github.com/kubernetes/community/blob/master/contributors/devel/sig-architecture/conformance-tests.md) 
+- [ ] (R) Production readiness review completed
+- [ ] (R) Production readiness review approved
+- [ ] "Implementation History" section is up-to-date for milestone
+- [ ] User-facing documentation has been created in [kubernetes/website], for publication to [kubernetes.io]
+- [ ] Supporting documentation—e.g., additional design documents, links to mailing list discussions/SIG meetings, relevant PRs/issues, release notes
+
+[kubernetes.io]: https://kubernetes.io/
+[kubernetes/enhancements]: https://git.k8s.io/enhancements
+[kubernetes/kubernetes]: https://git.k8s.io/kubernetes
+[kubernetes/website]: https://git.k8s.io/website
+
+## Summary
+
+After kubelet is restarted, it looses track of all volume it mounted for
+running Pods. It tries to restore this state from the API server, where kubelet
+can find Pods that _should_ be running, and from the host's OS, where it can
+find actually mounted volumes. We know this process is imperfect.
+This KEP tries to rework the process. While the work is technically a bugfix,
+it changes large parts of kubelet, and we'd like to have it behind a feature
+gate to provide users a way to get to the old implementations in case of
+problems.
+
+This work started as part of
+[KEP 1790](https://github.com/kubernetes/enhancements/tree/master/keps/sig-storage/1710-selinux-relabeling)
+and even went alpha in v1.26, but we'd like to have a separate feature + feature
+gate to be able to graduate VolumeManager reconstruction faster.
+
+<!--
+This section is incredibly important for producing high-quality, user-focused
+documentation such as release notes or a development roadmap. It should be
+possible to collect this information before implementation begins, in order to
+avoid requiring implementors to split their attention between writing release
+notes and implementing the feature itself. KEP editors and SIG Docs
+should help to ensure that the tone and content of the `Summary` section is
+useful for a wide audience.
+
+A good summary is probably at least a paragraph in length.
+
+Both in this section and below, follow the guidelines of the [documentation
+style guide]. In particular, wrap lines to a reasonable length, to make it
+easier for reviewers to cite specific portions, and to minimize diff churn on
+updates.
+
+[documentation style guide]: https://github.com/kubernetes/community/blob/master/contributors/guide/style-guide.md
+-->
+
+## Motivation
+
+### Goals
+
+* During kubelet startup, allow it to populate additional information about
+  _how_ are existing volumes mounted.
+  [KEP 1710](https://github.com/kubernetes/enhancements/tree/master/keps/sig-storage/1710-selinux-relabeling)
+  needs to know what mount options did the previous kubelet used when mounting
+  the volumes, to be able to tell if they need any change or not.
+* Fix [#105536](https://github.com/kubernetes/kubernetes/issues/105536): Volumes
+  are not cleaned up (unmounted) after kubelet restart, which needs a similar
+  VolumeManager refactoring.
+* In general, make volume cleanup more robust.
+
+<!--
+List the specific goals of the KEP. What is it trying to achieve? How will we
+know that this has succeeded?
+-->
+
+### Non-Goals
+ 
+<!--
+What is out of scope for this KEP? Listing non-goals helps to focus discussion
+and make progress.
+-->
+
+## Introduction
+
+*VolumeManager* is a piece of kubelet that mounts volumes that should be
+mounted (i.e. a Pod that needs the volume exists) and unmounts volumes that are
+not needed any longer (all Pods that used them were deleted).
+
+VolumeManager keeps two caches:
+* *DesiredStateOfWorld* (DSW) contains volumes that should be mounted.
+* *ActualStateOfWorld* (ASW) contains currently mounted volumes.
+
+VolumeManager then compares these two caches and tries to move ASW towards DSW.
+
+Both caches exist only in memory and are lost when kubelet process dies. It's
+relatively easy to populate DSW - just list all Pods from the API server
+(and static pods and whatnot) and collect their volumes.
+
+*Volume reconstruction* is a process where kubelet tries to create a single
+valid `PersistentVolumeSpec` or `VolumeSpec` for a volume from the OS.
+Typically from mount table by looking at what's mounted at 
+`/var/lib/kubelet/pods/*/volumes/XYZ`. This process is imperfect,
+it populates only `(Persistent)VolumeSpec` fields that are necessary to unmount
+the volume (i.e. to call `volumePlugin.TearDown` + `UnmountDevice` calls).
+
+Today, kubelet populates VolumeManager's DSW first, from static Pods and pods
+received from the API server. ASW is populated from the OS
+after DSW is complete and **only volumes missing in DSW are added there**.
+In other words, kubelet reconstructs only the volumes for Pods that were running
+before kubelet started, but they were delered when kubelet started. (If the pod
+was Running, its volumes would be in DSW).
+
+We assumed that this was enough, because if a volume is in DSW, the
+VolumeManager will try to mount the volume, and it will eventually reach ASW. 
+
+We needed to add
+[a complex workaround](https://github.com/kubernetes/kubernetes/pull/110670)
+to actually unmount a volume if it's initially in DSW, but user deletes all
+Pods that need it before the volume reaches ASW. 
+
+## Proposal
+
+<!--
+This is where we get down to the specifics of what the proposal actually is.
+This should have enough detail that reviewers can understand exactly what
+you're proposing, but should not include things like API designs or
+implementation. What is the desired outcome and how do we measure success?.
+The "Design Details" section below is for the real
+nitty-gritty.
+-->
+
+We propose to reverse the kubelet startup process.
+
+1. Quickly reconstruct ASW from the OS and add **all** found volumes to ASW
+   when kubelet starts. "Quickly" means the process should look only at the OS 
+   and files/directories in `/var/lib/kubelet/` and it should not
+   require the API server or any network calls. Esp. the API server may
+   not be available at this stage of kubelet startup.
+2. Once all mounted volumes are in ASW, start populating DSW from static Pods
+   and Pods received from the API server.
+3. When connection to the API server becomes available, complete information
+   in ASW with data from the API server (e.g. from `node.status`). This
+   typically happens in parallel to the previous step.
+
+Benefits:
+
+* All volumes are reconstructed from the OS. As result, ASW can contain the
+  real information how are the volumes mounted, e.g. their mount options.
+  This will help with
+  [KEP 1710](https://github.com/kubernetes/enhancements/tree/master/keps/sig-storage/1710-selinux-relabeling).
+* Some issues become much easier to fix, e.g.
+  * [#105536](https://github.com/kubernetes/kubernetes/issues/105536)
+  * We can remove workarounds for
+    [#96635](https://github.com/kubernetes/kubernetes/issues/96635)
+    and [#70044](https://github.com/kubernetes/kubernetes/issues/70044),
+    they will get fixed naturally by the refactoring.
+    
+We also propose to split this work out of
+[KEP 1710](https://github.com/kubernetes/enhancements/tree/master/keps/sig-storage/1710-selinux-relabeling),
+as it can be useful outside of SELinux relabeling and could graduate separately.
+to split the feature, we propose feature gate `NewVolumeManagerReconstruction`.
+
+### User Stories (Optional)
+
+#### Story 1
+
+(This is not a new story, we want to keep this behavior)
+
+As a cluster admin, I want kubelet to resume where it stopped when it was
+restarted or its machine was rebooted. It must be able to recognize what
+happened in the meantime and either unmount any volumes of Pods that were
+deleted in the API server or mount volumes for newly created Pods. 
+
+### Notes/Constraints/Caveats (Optional)
+
+TODO: delete?
+
+<!--
+What are the caveats to the proposal?
+What are some important details that didn't come across above?
+Go in to as much detail as necessary here.
+This might be a good place to talk about core concepts and how they relate.
+-->
+
+### Risks and Mitigations
+
+The whole VolumeManager startup was rewritten as part of
+[KEP 1710](https://github.com/kubernetes/enhancements/tree/master/keps/sig-storage/1710-selinux-relabeling).
+It can contain bugs that are not trivial to find, because kubelet can be used
+in number of situations that we don't have in CI. For example, we found out
+(and fixed) a case where the API server is actually a static Pod in kubelet
+that is starting. We don't know what other kubelet configurations people use,
+so we decided to write a KEP and move the new VolumeManager startup behind
+a feature gate.
+
+
+## Design Details
+
+### Proposed VolumeManager startup
+
+When kubelet starts:
+
+1. VolumeManager starts populating DSW from PodManager, who reads Pods from
+   static pods and/or the API server.
+
+2. In parallel to 1., VolumeManager scans `/var/lib/kubelet/pods/*` and
+   reconstructs *all* found volumes and adds them to ASW as *uncertain*. I.e.
+   depending on DSW, the VolumeManager will either call `volumePlugin.SetUp()`
+   to make sure the volume is fully mounted or it will call
+   `volumePlugin.TearDown()` to make sure the volume is unmounted. Only
+   information that is available in the Pod directory on the disk are
+   reconstructed into ASW at this point.
+   * Since the volume reconstruction can be imperfect and can miss `devicePath`,
+     VolumeManager adds all reconstructed volumes to `volumesNeedDevicePath`
+     array, to finish their reconstruction from `node.status.volumesAttached`
+   * All volumes that failed reconstruction are added to
+     `volumesFailedReconstruction` list.
+
+
+After **ASW** is populated, VolumeManager starts its reconciliation loop, i.e.
+starts comparing ASW and DSW and periodically calls:
+1. `mountOrAttachVolumes()` - mounts (and attaches, if necessary) volumes that
+   are in DSW, but not in ASW. This can happen even before DSW is fully
+   populated, because ASW is fully populated at this point.
+
+2. `updateReconstructedDevicePaths()` - once kubelet gets connection to the API
+   server and reads its own `Node.status`, volumes in `volumesNeedDevicePath`
+   (i.e. all reconstructed volumes) are updated from
+   `node.status.attachedVolumes`. This happens only once,
+   `volumesNeedDevicePath` is cleared afterwards.
+
+3. (Only once): Add all reconstructed volumes to `node.status.volumesInUse`.
+   
+4. Only after DSW was fully populated (i.e. it contains at least Pods that were
+   Running when kubelet started), **and** `devicePaths` were populated from
+   `node.status`, VolumeManager can start unmounting volumes and calls:
+   1. `unmountVolumes()` - unmounts (`TearDown`) pod local volumes that are in
+      ASW and are not in DSW.
+   2. `unmountDetachDevices()` - unmounts (`UnmountDevice`) global volume mounts
+      of volumes that are in ASW and are not in DSW.
+   3. `cleanOrphanVolumes()` - tries to clean up `volumesFailedReconstruction`. 
+      Here kubelet cannot call appropriate volume plugin to unmount a
+      volume, because kubelet failed to reconstruct the volume spec from
+      `/var/lib/kubelet/pods/<uid>/volumes/xyz`. Kubelet at least tries to
+      unmount the directory and clean up any orphan files there.
+
+Note that e.g. `mountOrAttachVolumes` can call `volumePlugin.MountDevice` /
+`SetUp()` on a reconstructed volume (because it's *uncertain*) and finally
+update ASW, while the VolumeManager is still waiting for the API server to
+update `devicePath` of the same volume in ASW (step 2. above).
+We made sure that `updateReconstructedDevicePaths` will update the
+`devicePath` only for *uncertain* volumes, not to overwrite the *certain* ones.
+
+### Old VolumeManager startup
+
+When kubelet starts:
+
+1. VolumeManager starts populating DSW from PodManager, who reads Pods from
+   static pods and/or the API server.
+
+While DSW populator runs in the another thread, VolumeManager starts its
+reconciliation loop. Note that ASW is empty at this point + DSW is being
+populated. It starts comparing ASW and DSW and periodically following calls: 
+
+1. `unmountVolumes()` - unmounts (`TearDown`) pod local volumes that are in
+   ASW and are not in DSW. Since the ASW is initially empty, this call
+   becomes useful later.
+2. `mountOrAttachVolumes()` - mounts (and attaches, if necessary) volumes that
+   are in DSW, but not in ASW. This will eventually happen for all volumes in
+   DSW, because ASW is empty. This actually the way how AWS is populated.
+3. `unmountDetachDevices()` - unmounts (`UnmountDevice`) global volume mounts
+   of volumes that are in ASW and are not in DSW.
+4. Only once after DSW is fully populated (i.e. it contains at least Pods that
+   were Running when kubelet started):
+   1. VolumeManager scans `/var/lib/kubelet/pods/*`
+      and reconstructs **only** volumes that are not in DSW. (If a volume is in
+      DSW, we expect that it reaches ASW during step 3.)
+      * `devicePath` of reconstructed volumes is populated from
+        `node.status.attachedVolumes` right away.
+      * In the next reconciliation loop, reconstructed volumes that are not in
+        DSW are finally unmounted in step 1. above.
+      * TODO: mention the workaround for deleting Pods before their volumes
+        reach ASW.
+   2. VolumeManager reports all reconstructed volumes in
+      `node.status.volumesInUse`.
+    
+### Test Plan
+
+[x] 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.
+
+##### Prerequisite testing updates
+
+<!--
+Based on reviewers feedback describe what additional tests need to be added prior
+implementing this enhancement to ensure the enhancements have also solid foundations.
+-->
+
+##### Unit tests
+
+<!--
+In principle every added code should have complete unit test coverage, so providing
+the exact set of tests will not bring additional value.
+However, if complete unit test coverage is not possible, explain the reason of it
+together with explanation why this is acceptable.
+-->
+
+<!--
+Additionally, for Alpha try to enumerate the core package you will be touching
+to implement this enhancement and provide the current unit coverage for those
+in the form of:
+- <package>: <date> - <current test coverage>
+The data can be easily read from:
+https://testgrid.k8s.io/sig-testing-canaries#ci-kubernetes-coverage-unit
+
+This can inform certain test coverage improvements that we want to do before
+extending the production code to implement this enhancement.
+-->
+
+- `<package>`: `<date>` - `<test coverage>`
+
+##### Integration tests
+
+<!--
+This question should be filled when targeting a release.
+For Alpha, describe what tests will be added to ensure proper quality of the enhancement.
+
+For Beta and GA, add links to added tests together with links to k8s-triage for those tests:
+https://storage.googleapis.com/k8s-triage/index.html
+-->
+
+- <test>: <link to test coverage>
+
+##### e2e tests
+
+<!--
+This question should be filled when targeting a release.
+For Alpha, describe what tests will be added to ensure proper quality of the enhancement.
+
+For Beta and GA, add links to added tests together with links to k8s-triage for those tests:
+https://storage.googleapis.com/k8s-triage/index.html
+
+We expect no non-infra related flakes in the last month as a GA graduation criteria.
+-->
+
+- <test>: <link to test coverage>
+
+### Graduation Criteria
+
+<!--
+**Note:** *Not required until targeted at a release.*
+
+Define graduation milestones.
+
+These may be defined in terms of API maturity, [feature gate] graduations, or as
+something else. The KEP should keep this high-level with a focus on what
+signals will be looked at to determine graduation.
+
+Consider the following in developing the graduation criteria for this enhancement:
+- [Maturity levels (`alpha`, `beta`, `stable`)][maturity-levels]
+- [Feature gate][feature gate] lifecycle
+- [Deprecation policy][deprecation-policy]
+
+Clearly define what graduation means by either linking to the [API doc
+definition](https://kubernetes.io/docs/concepts/overview/kubernetes-api/#api-versioning)
+or by redefining what graduation means.
+
+In general we try to use the same stages (alpha, beta, GA), regardless of how the
+functionality is accessed.
+
+[feature gate]: https://git.k8s.io/community/contributors/devel/sig-architecture/feature-gates.md
+[maturity-levels]: https://git.k8s.io/community/contributors/devel/sig-architecture/api_changes.md#alpha-beta-and-stable-versions
+[deprecation-policy]: https://kubernetes.io/docs/reference/using-api/deprecation-policy/
+
+Below are some examples to consider, in addition to the aforementioned [maturity levels][maturity-levels].
+
+#### Alpha
+
+- Feature implemented behind a feature flag
+- Initial e2e tests completed and enabled
+
+#### Beta
+
+- Gather feedback from developers and surveys
+- Complete features A, B, C
+- Additional tests are in Testgrid and linked in KEP
+
+#### GA
+
+- N examples of real-world usage
+- N installs
+- More rigorous forms of testing—e.g., downgrade tests and scalability tests
+- Allowing time for feedback
+
+**Note:** Generally we also wait at least two releases between beta and
+GA/stable, because there's no opportunity for user feedback, or even bug reports,
+in back-to-back releases.
+
+**For non-optional features moving to GA, the graduation criteria must include
+[conformance tests].**
+
+[conformance tests]: https://git.k8s.io/community/contributors/devel/sig-architecture/conformance-tests.md
+
+#### Deprecation
+
+- Announce deprecation and support policy of the existing flag
+- Two versions passed since introducing the functionality that deprecates the flag (to address version skew)
+- Address feedback on usage/changed behavior, provided on GitHub issues
+- Deprecate the flag
+-->
+
+### Upgrade / Downgrade Strategy
+
+<!--
+If applicable, how will the component be upgraded and downgraded? Make sure
+this is in the test plan.
+
+Consider the following in developing an upgrade/downgrade strategy for this
+enhancement:
+- What changes (in invocations, configurations, API use, etc.) is an existing
+  cluster required to make on upgrade, in order to maintain previous behavior?
+- What changes (in invocations, configurations, API use, etc.) is an existing
+  cluster required to make on upgrade, in order to make use of the enhancement?
+-->
+
+### Version Skew Strategy
+
+<!--
+If applicable, how will the component handle version skew with other
+components? What are the guarantees? Make sure this is in the test plan.
+
+Consider the following in developing a version skew strategy for this
+enhancement:
+- Does this enhancement involve coordinating behavior in the control plane and
+  in the kubelet? How does an n-2 kubelet without this feature available behave
+  when this feature is used?
+- Will any other components on the node change? For example, changes to CSI,
+  CRI or CNI may require updating that component before the kubelet.
+-->
+
+## Production Readiness Review Questionnaire
+
+<!--
+
+Production readiness reviews are intended to ensure that features merging into
+Kubernetes are observable, scalable and supportable; can be safely operated in
+production environments, and can be disabled or rolled back in the event they
+cause increased failures in production. See more in the PRR KEP at
+https://git.k8s.io/enhancements/keps/sig-architecture/1194-prod-readiness.
+
+The production readiness review questionnaire must be completed and approved
+for the KEP to move to `implementable` status and be included in the release.
+
+In some cases, the questions below should also have answers in `kep.yaml`. This
+is to enable automation to verify the presence of the review, and to reduce review
+burden and latency.
+
+The KEP must have a approver from the
+[`prod-readiness-approvers`](http://git.k8s.io/enhancements/OWNERS_ALIASES)
+team. Please reach out on the
+[#prod-readiness](https://kubernetes.slack.com/archives/CPNHUMN74) channel if
+you need any help or guidance.
+-->
+
+### Feature Enablement and Rollback
+
+<!--
+This section must be completed when targeting alpha to a release.
+-->
+
+###### How can this feature be enabled / disabled in a live cluster?
+
+<!--
+Pick one of these and delete the rest.
+
+Documentation is available on [feature gate lifecycle] and expectations, as
+well as the [existing list] of feature gates.
+
+[feature gate lifecycle]: https://git.k8s.io/community/contributors/devel/sig-architecture/feature-gates.md
+[existing list]: https://kubernetes.io/docs/reference/command-line-tools-reference/feature-gates/
+-->
+
+- [ ] Feature gate (also fill in values in `kep.yaml`)
+  - Feature gate name:
+  - Components depending on the feature gate:
+- [ ] Other
+  - Describe the mechanism:
+  - Will enabling / disabling the feature require downtime of the control
+    plane?
+  - Will enabling / disabling the feature require downtime or reprovisioning
+    of a node? (Do not assume `Dynamic Kubelet Config` feature is enabled).
+
+###### Does enabling the feature change any default behavior?
+
+<!--
+Any change of default behavior may be surprising to users or break existing
+automations, so be extremely careful here.
+-->
+
+###### Can the feature be disabled once it has been enabled (i.e. can we roll back the enablement)?
+
+<!--
+Describe the consequences on existing workloads (e.g., if this is a runtime
+feature, can it break the existing applications?).
+
+Feature gates are typically disabled by setting the flag to `false` and
+restarting the component. No other changes should be necessary to disable the
+feature.
+
+NOTE: Also set `disable-supported` to `true` or `false` in `kep.yaml`.
+-->
+
+###### What happens if we reenable the feature if it was previously rolled back?
+
+###### Are there any tests for feature enablement/disablement?
+
+<!--
+The e2e framework does not currently support enabling or disabling feature
+gates. However, unit tests in each component dealing with managing data, created
+with and without the feature, are necessary. At the very least, think about
+conversion tests if API types are being modified.
+
+Additionally, for features that are introducing a new API field, unit tests that
+are exercising the `switch` of feature gate itself (what happens if I disable a
+feature gate after having objects written with the new field) are also critical.
+You can take a look at one potential example of such test in:
+https://github.com/kubernetes/kubernetes/pull/97058/files#diff-7826f7adbc1996a05ab52e3f5f02429e94b68ce6bce0dc534d1be636154fded3R246-R282
+-->
+
+### Rollout, Upgrade and Rollback Planning
+
+<!--
+This section must be completed when targeting beta to a release.
+-->
+
+###### How can a rollout or rollback fail? Can it impact already running workloads?
+
+<!--
+Try to be as paranoid as possible - e.g., what if some components will restart
+mid-rollout?
+
+Be sure to consider highly-available clusters, where, for example,
+feature flags will be enabled on some API servers and not others during the
+rollout. Similarly, consider large clusters and how enablement/disablement
+will rollout across nodes.
+-->
+
+###### What specific metrics should inform a rollback?
+
+<!--
+What signals should users be paying attention to when the feature is young
+that might indicate a serious problem?
+-->
+
+###### Were upgrade and rollback tested? Was the upgrade->downgrade->upgrade path tested?
+
+<!--
+Describe manual testing that was done and the outcomes.
+Longer term, we may want to require automated upgrade/rollback tests, but we
+are missing a bunch of machinery and tooling and can't do that now.
+-->
+
+###### Is the rollout accompanied by any deprecations and/or removals of features, APIs, fields of API types, flags, etc.?
+
+<!--
+Even if applying deprecation policies, they may still surprise some users.
+-->
+
+### Monitoring Requirements
+
+<!--
+This section must be completed when targeting beta to a release.
+
+For GA, this section is required: approvers should be able to confirm the
+previous answers based on experience in the field.
+-->
+
+###### How can an operator determine if the feature is in use by workloads?
+
+<!--
+Ideally, this should be a metric. Operations against the Kubernetes API (e.g.,
+checking if there are objects with field X set) may be a last resort. Avoid
+logs or events for this purpose.
+-->
+
+###### How can someone using this feature know that it is working for their instance?
+
+<!--
+For instance, if this is a pod-related feature, it should be possible to determine if the feature is functioning properly
+for each individual pod.
+Pick one more of these and delete the rest.
+Please describe all items visible to end users below with sufficient detail so that they can verify correct enablement
+and operation of this feature.
+Recall that end users cannot usually observe component logs or access metrics.
+-->
+
+- [ ] Events
+  - Event Reason: 
+- [ ] API .status
+  - Condition name: 
+  - Other field: 
+- [ ] Other (treat as last resort)
+  - Details:
+
+###### What are the reasonable SLOs (Service Level Objectives) for the enhancement?
+
+<!--
+This is your opportunity to define what "normal" quality of service looks like
+for a feature.
+
+It's impossible to provide comprehensive guidance, but at the very
+high level (needs more precise definitions) those may be things like:
+  - per-day percentage of API calls finishing with 5XX errors <= 1%
+  - 99% percentile over day of absolute value from (job creation time minus expected
+    job creation time) for cron job <= 10%
+  - 99.9% of /health requests per day finish with 200 code
+
+These goals will help you determine what you need to measure (SLIs) in the next
+question.
+-->
+
+###### What are the SLIs (Service Level Indicators) an operator can use to determine the health of the service?
+
+<!--
+Pick one more of these and delete the rest.
+-->
+
+- [ ] Metrics
+  - Metric name:
+  - [Optional] Aggregation method:
+  - Components exposing the metric:
+- [ ] Other (treat as last resort)
+  - Details:
+
+###### Are there any missing metrics that would be useful to have to improve observability of this feature?
+
+<!--
+Describe the metrics themselves and the reasons why they weren't added (e.g., cost,
+implementation difficulties, etc.).
+-->
+
+### Dependencies
+
+<!--
+This section must be completed when targeting beta to a release.
+-->
+
+###### Does this feature depend on any specific services running in the cluster?
+
+<!--
+Think about both cluster-level services (e.g. metrics-server) as well
+as node-level agents (e.g. specific version of CRI). Focus on external or
+optional services that are needed. For example, if this feature depends on
+a cloud provider API, or upon an external software-defined storage or network
+control plane.
+
+For each of these, fill in the following—thinking about running existing user workloads
+and creating new ones, as well as about cluster-level services (e.g. DNS):
+  - [Dependency name]
+    - Usage description:
+      - Impact of its outage on the feature:
+      - Impact of its degraded performance or high-error rates on the feature:
+-->
+
+### Scalability
+
+<!--
+For alpha, this section is encouraged: reviewers should consider these questions
+and attempt to answer them.
+
+For beta, this section is required: reviewers must answer these questions.
+
+For GA, this section is required: approvers should be able to confirm the
+previous answers based on experience in the field.
+-->
+
+###### Will enabling / using this feature result in any new API calls?
+
+<!--
+Describe them, providing:
+  - API call type (e.g. PATCH pods)
+  - estimated throughput
+  - originating component(s) (e.g. Kubelet, Feature-X-controller)
+Focusing mostly on:
+  - components listing and/or watching resources they didn't before
+  - API calls that may be triggered by changes of some Kubernetes resources
+    (e.g. update of object X triggers new updates of object Y)
+  - periodic API calls to reconcile state (e.g. periodic fetching state,
+    heartbeats, leader election, etc.)
+-->
+
+###### Will enabling / using this feature result in introducing new API types?
+
+<!--
+Describe them, providing:
+  - API type
+  - Supported number of objects per cluster
+  - Supported number of objects per namespace (for namespace-scoped objects)
+-->
+
+###### Will enabling / using this feature result in any new calls to the cloud provider?
+
+<!--
+Describe them, providing:
+  - Which API(s):
+  - Estimated increase:
+-->
+
+###### Will enabling / using this feature result in increasing size or count of the existing API objects?
+
+<!--
+Describe them, providing:
+  - API type(s):
+  - Estimated increase in size: (e.g., new annotation of size 32B)
+  - Estimated amount of new objects: (e.g., new Object X for every existing Pod)
+-->
+
+###### Will enabling / using this feature result in increasing time taken by any operations covered by existing SLIs/SLOs?
+
+<!--
+Look at the [existing SLIs/SLOs].
+
+Think about adding additional work or introducing new steps in between
+(e.g. need to do X to start a container), etc. Please describe the details.
+
+[existing SLIs/SLOs]: https://git.k8s.io/community/sig-scalability/slos/slos.md#kubernetes-slisslos
+-->
+
+###### Will enabling / using this feature result in non-negligible increase of resource usage (CPU, RAM, disk, IO, ...) in any components?
+
+<!--
+Things to keep in mind include: additional in-memory state, additional
+non-trivial computations, excessive access to disks (including increased log
+volume), significant amount of data sent and/or received over network, etc.
+This through this both in small and large cases, again with respect to the
+[supported limits].
+
+[supported limits]: https://git.k8s.io/community//sig-scalability/configs-and-limits/thresholds.md
+-->
+
+### Troubleshooting
+
+<!--
+This section must be completed when targeting beta to a release.
+
+For GA, this section is required: approvers should be able to confirm the
+previous answers based on experience in the field.
+
+The Troubleshooting section currently serves the `Playbook` role. We may consider
+splitting it into a dedicated `Playbook` document (potentially with some monitoring
+details). For now, we leave it here.
+-->
+
+###### How does this feature react if the API server and/or etcd is unavailable?
+
+###### What are other known failure modes?
+
+<!--
+For each of them, fill in the following information by copying the below template:
+  - [Failure mode brief description]
+    - Detection: How can it be detected via metrics? Stated another way:
+      how can an operator troubleshoot without logging into a master or worker node?
+    - Mitigations: What can be done to stop the bleeding, especially for already
+      running user workloads?
+    - Diagnostics: What are the useful log messages and their required logging
+      levels that could help debug the issue?
+      Not required until feature graduated to beta.
+    - Testing: Are there any tests for failure mode? If not, describe why.
+-->
+
+###### What steps should be taken if SLOs are not being met to determine the problem?
+
+## Implementation History
+
+<!--
+Major milestones in the lifecycle of a KEP should be tracked in this section.
+Major milestones might include:
+- the `Summary` and `Motivation` sections being merged, signaling SIG acceptance
+- the `Proposal` section being merged, signaling agreement on a proposed design
+- the date implementation started
+- the first Kubernetes release where an initial version of the KEP was available
+- the version of Kubernetes where the KEP graduated to general availability
+- when the KEP was retired or superseded
+-->
+
+## Drawbacks
+
+<!--
+Why should this KEP _not_ be implemented?
+-->
+
+## Alternatives
+
+<!--
+What other approaches did you consider, and why did you rule them out? These do
+not need to be as detailed as the proposal, but should include enough
+information to express the idea and why it was not acceptable.
+-->
+
+## Infrastructure Needed (Optional)
+
+<!--
+Use this section if you need things from the project/SIG. Examples include a
+new subproject, repos requested, or GitHub details. Listing these here allows a
+SIG to get the process for these resources started right away.
+-->
diff --git a/keps/sig-storage/3756-volume-reconstruction/kep.yaml b/keps/sig-storage/3756-volume-reconstruction/kep.yaml
new file mode 100644
index 000000000000..9c8ad9cf40ff
--- /dev/null
+++ b/keps/sig-storage/3756-volume-reconstruction/kep.yaml
@@ -0,0 +1,44 @@
+title: Robust VolumeManager reconstruction after kubelet restart
+kep-number: 3756
+authors:
+  - "@jsafrane"
+owning-sig: sig-storage
+participating-sigs:
+status: provisional
+creation-date: 2023-01-20
+reviewers:
+  - "@msau42"
+  - "@gnufied"
+  - "@jingxu97"
+approvers:
+  - "@msau42"
+see-also:
+  - "/keps/sig-storage/1710-selinux-relabeling"
+replaces:
+
+# The target maturity stage in the current dev cycle for this KEP.
+stage: beta
+
+# The most recent milestone for which work toward delivery of this KEP has been
+# done. This can be the current (upcoming) milestone, if it is being actively
+# worked on.
+latest-milestone: "v1.27"
+
+# The milestone at which this feature was, or is targeted to be, at each stage.
+milestone:
+  alpha: "v1.26" # as part of /keps/sig-storage/1710-selinux-relabeling
+  beta: "v1.27"
+  stable: "v1.29"
+
+# The following PRR answers are required at alpha release
+# List the feature gate name and the components for which it must be enabled
+feature-gates:
+  - name: NewVolumeManagerReconstruction
+    components:
+      - kubelet
+
+disable-supported: true
+
+# The following PRR answers are required at beta release
+metrics:
+#  - TODO: my_feature_metric