API changes for Pod Level Resources

1. Add Resources struct to PodSpec struct in both external and internal API packages
2. Adding feature gate and logic for dropping disabled fields for Pod Level Resources
KEP: enhancements/keps/sig-node/2837-pod-level-resource-spec

Author: ndixita

pkg/api/pod/util.go

@@ -621,6 +621,7 @@ func dropDisabledFields(
 		}
 	}
 
+	dropDisabledPodLevelResources(podSpec, oldPodSpec)
 	dropDisabledProcMountField(podSpec, oldPodSpec)
 
 	dropDisabledNodeInclusionPolicyFields(podSpec, oldPodSpec)
@@ -674,6 +675,14 @@ func dropDisabledFields(
 	dropSELinuxChangePolicy(podSpec, oldPodSpec)
 }
 
+func dropDisabledPodLevelResources(podSpec, oldPodSpec *api.PodSpec) {
+	// If the feature is disabled and not in use, drop Resources at the pod-level
+	// from PodSpec.
+	if !utilfeature.DefaultFeatureGate.Enabled(features.PodLevelResources) && !podLevelResourcesInUse(oldPodSpec) {
+		podSpec.Resources = nil
+	}
+}
+
 func dropPodLifecycleSleepAction(podSpec, oldPodSpec *api.PodSpec) {
 	if utilfeature.DefaultFeatureGate.Enabled(features.PodLifecycleSleepAction) || podLifecycleSleepActionInUse(oldPodSpec) {
 		return
@@ -1050,6 +1059,28 @@ func supplementalGroupsPolicyInUse(podSpec *api.PodSpec) bool {
 	return false
 }
 
+// podLevelResourcesInUse returns true if pod-spec is non-nil and Resources field at
+// pod-level has non-empty Requests or Limits.
+func podLevelResourcesInUse(podSpec *api.PodSpec) bool {
+	if podSpec == nil {
+		return false
+	}
+
+	if podSpec.Resources == nil {
+		return false
+	}
+
+	if len(podSpec.Resources.Requests) > 0 {
+		return true
+	}
+
+	if len(podSpec.Resources.Limits) > 0 {
+		return true
+	}
+
+	return false
+}
+
 // inPlacePodVerticalScalingInUse returns true if pod spec is non-nil and ResizePolicy is set
 func inPlacePodVerticalScalingInUse(podSpec *api.PodSpec) bool {
 	if podSpec == nil {

pkg/api/pod/util_test.go

@@ -2703,6 +2703,149 @@ func TestDropInPlacePodVerticalScaling(t *testing.T) {
 	}
 }
 
+func TestDropPodLevelResources(t *testing.T) {
+	containers := []api.Container{
+		{
+			Name:  "c1",
+			Image: "image",
+			Resources: api.ResourceRequirements{
+				Requests: api.ResourceList{api.ResourceCPU: resource.MustParse("100m")},
+				Limits:   api.ResourceList{api.ResourceCPU: resource.MustParse("200m")},
+			},
+		},
+	}
+	podWithPodLevelResources := func() *api.Pod {
+		return &api.Pod{
+			Spec: api.PodSpec{
+				Resources: &api.ResourceRequirements{
+					Requests: api.ResourceList{
+						api.ResourceCPU:    resource.MustParse("100m"),
+						api.ResourceMemory: resource.MustParse("50Gi"),
+					},
+					Limits: api.ResourceList{
+						api.ResourceCPU:    resource.MustParse("100m"),
+						api.ResourceMemory: resource.MustParse("50Gi"),
+					},
+				},
+				Containers: containers,
+			},
+		}
+	}
+
+	podWithoutPodLevelResources := func() *api.Pod {
+		return &api.Pod{
+			Spec: api.PodSpec{
+				Containers: containers,
+			},
+		}
+	}
+
+	podInfo := []struct {
+		description          string
+		hasPodLevelResources bool
+		pod                  func() *api.Pod
+	}{
+		{
+			description:          "has pod-level resources",
+			hasPodLevelResources: true,
+			pod:                  podWithPodLevelResources,
+		},
+		{
+			description:          "does not have pod-level resources",
+			hasPodLevelResources: false,
+			pod:                  podWithoutPodLevelResources,
+		},
+		{
+			description:          "is nil",
+			hasPodLevelResources: false,
+			pod:                  func() *api.Pod { return nil },
+		},
+		{
+			description:          "is empty struct",
+			hasPodLevelResources: false,
+			// refactor to generalize and use podWithPodLevelResources()
+			pod: func() *api.Pod {
+				return &api.Pod{
+					Spec: api.PodSpec{
+						Resources:  &api.ResourceRequirements{},
+						Containers: containers,
+					},
+				}
+			},
+		},
+		{
+			description:          "is empty Requests list",
+			hasPodLevelResources: false,
+			pod: func() *api.Pod {
+				return &api.Pod{
+					Spec: api.PodSpec{Resources: &api.ResourceRequirements{
+						Requests: api.ResourceList{},
+					}}}
+			},
+		},
+		{
+			description:          "is empty Limits list",
+			hasPodLevelResources: false,
+			pod: func() *api.Pod {
+				return &api.Pod{
+					Spec: api.PodSpec{Resources: &api.ResourceRequirements{
+						Limits: api.ResourceList{},
+					}}}
+			},
+		},
+	}
+
+	for _, enabled := range []bool{true, false} {
+		for _, oldPodInfo := range podInfo {
+			for _, newPodInfo := range podInfo {
+				oldPodHasPodLevelResources, oldPod := oldPodInfo.hasPodLevelResources, oldPodInfo.pod()
+				newPodHasPodLevelResources, newPod := newPodInfo.hasPodLevelResources, newPodInfo.pod()
+				if newPod == nil {
+					continue
+				}
+
+				t.Run(fmt.Sprintf("feature enabled=%v, old pod %v, new pod %v", enabled, oldPodInfo.description, newPodInfo.description), func(t *testing.T) {
+					featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, features.PodLevelResources, enabled)
+
+					var oldPodSpec *api.PodSpec
+					if oldPod != nil {
+						oldPodSpec = &oldPod.Spec
+					}
+
+					dropDisabledFields(&newPod.Spec, nil, oldPodSpec, nil)
+
+					// old pod should never be changed
+					if !reflect.DeepEqual(oldPod, oldPodInfo.pod()) {
+						t.Errorf("old pod changed: %v", cmp.Diff(oldPod, oldPodInfo.pod()))
+					}
+
+					switch {
+					case enabled || oldPodHasPodLevelResources:
+						// new pod shouldn't change if feature enabled or if old pod has
+						// any pod level resources
+						if !reflect.DeepEqual(newPod, newPodInfo.pod()) {
+							t.Errorf("new pod changed: %v", cmp.Diff(newPod, newPodInfo.pod()))
+						}
+					case newPodHasPodLevelResources:
+						// new pod should be changed
+						if reflect.DeepEqual(newPod, newPodInfo.pod()) {
+							t.Errorf("new pod was not changed")
+						}
+						// new pod should not have any pod-level resources
+						if !reflect.DeepEqual(newPod, podWithoutPodLevelResources()) {
+							t.Errorf("new pod has pod-level resources: %v", cmp.Diff(newPod, podWithoutPodLevelResources()))
+						}
+					default:
+						if newPod.Spec.Resources != nil {
+							t.Errorf("expected nil, got: %v", newPod.Spec.Resources)
+						}
+					}
+				})
+			}
+		}
+	}
+}
+
 func TestDropSidecarContainers(t *testing.T) {
 	containerRestartPolicyAlways := api.ContainerRestartPolicyAlways
 

pkg/apis/core/types.go

@@ -3609,6 +3609,20 @@ type PodSpec struct {
 	// +featureGate=DynamicResourceAllocation
 	// +optional
 	ResourceClaims []PodResourceClaim
+	// Resources is the total amount of CPU and Memory resources required by all
+	// containers in the pod. It supports specifying Requests and Limits for
+	// "cpu" and "memory" resource names only. ResourceClaims are not supported.
+	//
+	// This field enables fine-grained control over resource allocation for the
+	// entire pod, allowing resource sharing among containers in a pod.
+	// TODO: For beta graduation, expand this comment with a detailed explanation.
+	//
+	// This is an alpha field and requires enabling the PodLevelResources feature
+	// gate.
+	//
+	// +featureGate=PodLevelResources
+	// +optional
+	Resources *ResourceRequirements
 }
 
 // PodResourceClaim references exactly one ResourceClaim through a ClaimSource.

pkg/features/kube_features.go

@@ -835,6 +835,13 @@ const (
 	// Enables external service account JWT signing and key management.
 	// If enabled, it allows passing --service-account-signing-endpoint flag to configure external signer.
 	ExternalServiceAccountTokenSigner featuregate.Feature = "ExternalServiceAccountTokenSigner"
+
+	// owner: @ndixita
+	// key: https://kep.k8s.io/2837
+	// alpha: 1.32
+	//
+	// Enables specifying resources at pod-level.
+	PodLevelResources featuregate.Feature = "PodLevelResources"
 )
 
 func init() {

pkg/features/versioned_kube_features.go

@@ -567,6 +567,10 @@ var defaultVersionedKubernetesFeatureGates = map[featuregate.Feature]featuregate
 		{Version: version.MustParse("1.32"), Default: true, PreRelease: featuregate.GA, LockToDefault: true}, // remove in 1.35
 	},
 
+	PodLevelResources: {
+		{Version: version.MustParse("1.32"), Default: false, PreRelease: featuregate.Alpha},
+	},
+
 	PodLifecycleSleepAction: {
 		{Version: version.MustParse("1.29"), Default: false, PreRelease: featuregate.Alpha},
 		{Version: version.MustParse("1.30"), Default: true, PreRelease: featuregate.Beta},

staging/src/k8s.io/api/core/v1/types.go

@@ -4080,6 +4080,20 @@ type PodSpec struct {
 	// +featureGate=DynamicResourceAllocation
 	// +optional
 	ResourceClaims []PodResourceClaim `json:"resourceClaims,omitempty" patchStrategy:"merge,retainKeys" patchMergeKey:"name" protobuf:"bytes,39,rep,name=resourceClaims"`
+	// Resources is the total amount of CPU and Memory resources required by all
+	// containers in the pod. It supports specifying Requests and Limits for
+	// "cpu" and "memory" resource names only. ResourceClaims are not supported.
+	//
+	// This field enables fine-grained control over resource allocation for the
+	// entire pod, allowing resource sharing among containers in a pod.
+	// TODO: For beta graduation, expand this comment with a detailed explanation.
+	//
+	// This is an alpha field and requires enabling the PodLevelResources feature
+	// gate.
+	//
+	// +featureGate=PodLevelResources
+	// +optional
+	Resources *ResourceRequirements `json:"resources,omitempty" protobuf:"bytes,40,opt,name=resources"`
 }
 
 // PodResourceClaim references exactly one ResourceClaim, either directly