Update KEP for version skew strategy

Author: ehashman

keps/sig-node/2238-liveness-probe-grace-period/README.md

@@ -12,9 +12,9 @@
 - [Design Details](#design-details)
   - [Test Plan](#test-plan)
   - [Graduation Criteria](#graduation-criteria)
-    - [Alpha](#alpha)
-    - [Beta](#beta)
-    - [Graduation](#graduation)
+    - [Alpha (1.21)](#alpha-121)
+    - [Beta (1.22)](#beta-122)
+    - [Graduation (1.25)](#graduation-125)
   - [Upgrade / Downgrade Strategy](#upgrade--downgrade-strategy)
   - [Version Skew Strategy](#version-skew-strategy)
 - [Production Readiness Review Questionnaire](#production-readiness-review-questionnaire)
@@ -183,23 +183,27 @@ quickly.
 
 ### Graduation Criteria
 
-#### Alpha
+#### Alpha (1.21)
 
 - New probe field, `terminationGracePeriodSeconds`, is implemented and
   available behind a feature flag.
 - Appropriate tests are written.
 
-#### Beta
+#### Beta (1.22)
 
-- Feature flag is defaulted on.
+- Feature flag will default to off.
 - Remove feature gate from [kubelet](https://github.com/kubernetes/kubernetes/pull/99375#issuecomment-794680869).
+- Ensure that when feature gate is off in API server, probe-level
+  `TerminationGracePeriodSeconds` is blanked out.
 - Add validation to ensure `terminationGracePeriodSeconds` is non-negative.
+- Feature flag is defaulted to on after kube-apiserver is +2 versions of the
+  kubelet having the support (1.24).
 
 _Below graduation criteria are tentative._
 
-#### Graduation
+#### Graduation (1.25)
 
-- Feature flag is removed, feature is graduated.
+- Feature flag is removed, feature is graduated (1.25).
 
 ### Upgrade / Downgrade Strategy
 
@@ -238,7 +242,11 @@ enhancement:
 n-2 kubelet without this feature will default to the old behaviour, using the
 pod-level `terminationGracePeriodSeconds`.
 
-Only when feature gate is enabled for all components will we use the new field.
+Feature gate will be removed from kubelet in 1.22, ensuring support for n-2
+version skew on a 1.24+ API server.
+
+Only when feature gate is enabled for all components will we use the new field,
+so we delay defaulting the feature flag on until then.
 
 ## Production Readiness Review Questionnaire
 
@@ -292,7 +300,8 @@ _This section must be completed when targeting alpha to a release._
   Describe the consequences on existing workloads (e.g., if this is a runtime
   feature, can it break the existing applications?).
 
-  Yes: disable feature flag.
+  Yes: disable feature flag. API server will blank out values if it is set in
+  etcd while feature flag is disabled.
 
   While feature flag is enabled, the feature can also be disabled by unsetting
   the field on the Probe specification, which will restore the default

keps/sig-node/2238-liveness-probe-grace-period/kep.yaml

@@ -29,7 +29,7 @@ latest-milestone: "v1.22"
 milestone:
   alpha: "v1.21"
   beta: "v1.22"
-  stable: "v1.23"
+  stable: "v1.25"
 
 # The following PRR answers are required at alpha release
 # List the feature gate name and the components for which it must be enabled