Add feature flag ProbeTerminationGracePeriod, test field drop in API

pkg/api/pod/util.go

@@ -551,6 +551,20 @@ func dropDisabledFields(
 		})
 	}
 
+	if !utilfeature.DefaultFeatureGate.Enabled(features.ProbeTerminationGracePeriod) && !probeGracePeriodInUse(oldPodSpec) {
+		// Set pod-level terminationGracePeriodSeconds to nil if the feature is disabled and it is not used
+		VisitContainers(podSpec, AllContainers, func(c *api.Container, containerType ContainerType) bool {
+			if c.LivenessProbe != nil {
+				c.LivenessProbe.TerminationGracePeriodSeconds = nil
+			}
+			if c.StartupProbe != nil {
+				c.StartupProbe.TerminationGracePeriodSeconds = nil
+			}
+			// cannot be set for readiness probes
+			return true
+		})
+	}
+
 	dropDisabledFSGroupFields(podSpec, oldPodSpec)
 
 	if !utilfeature.DefaultFeatureGate.Enabled(features.PodOverhead) && !overheadInUse(oldPodSpec) {
@@ -811,6 +825,27 @@ func subpathExprInUse(podSpec *api.PodSpec) bool {
 	return inUse
 }
 
+// probeGracePeriodInUse returns true if the pod spec is non-nil and has a probe that makes use
+// of the probe-level terminationGracePeriodSeconds feature
+func probeGracePeriodInUse(podSpec *api.PodSpec) bool {
+	if podSpec == nil {
+		return false
+	}
+
+	var inUse bool
+	VisitContainers(podSpec, AllContainers, func(c *api.Container, containerType ContainerType) bool {
+		// cannot be set for readiness probes
+		if (c.LivenessProbe != nil && c.LivenessProbe.TerminationGracePeriodSeconds != nil) ||
+		   (c.StartupProbe != nil && c.StartupProbe.TerminationGracePeriodSeconds != nil) {
+			inUse = true
+			return false
+		}
+		return true
+	})
+
+	return inUse
+}
+
 // csiInUse returns true if any pod's spec include inline CSI volumes.
 func csiInUse(podSpec *api.PodSpec) bool {
 	if podSpec == nil {