APIs, Validation and condition enforcements

- New API field .spec.schedulingGates
- Validation and drop disabled fields
- Disallow binding a Pod carrying non-nil schedulingGates
- Disallow creating a Pod with non-nil nodeName and non-nil schedulingGates
- Adds a {type:PodScheduled, reason:WaitingForGates} condition if necessary
- New literal SchedulingGated in the STATUS column of `k get pod`

pkg/features/kube_features.go

@@ -643,6 +643,13 @@ const (
 	// sandbox creation and network configuration completes successfully
 	PodHasNetworkCondition featuregate.Feature = "PodHasNetworkCondition"
 
+	// owner: @Huang-Wei
+	// kep: https://kep.k8s.io/3521
+	// alpha: v1.26
+	//
+	// Enable users to specify when a Pod is ready for scheduling.
+	PodSchedulingReadiness featuregate.Feature = "PodSchedulingReadiness"
+
 	// owner: @liggitt, @tallclair, sig-auth
 	// alpha: v1.22
 	// beta: v1.23
@@ -995,6 +1002,8 @@ var defaultKubernetesFeatureGates = map[featuregate.Feature]featuregate.FeatureS
 
 	PodHasNetworkCondition: {Default: false, PreRelease: featuregate.Alpha},
 
+	PodSchedulingReadiness: {Default: false, PreRelease: featuregate.Alpha},
+
 	PodSecurity: {Default: true, PreRelease: featuregate.GA, LockToDefault: true},
 
 	ProbeTerminationGracePeriod: {Default: true, PreRelease: featuregate.Beta}, // Default to true in beta 1.25