pod-overhead: add Overhead to PodSpec internal type

Update internal PodSpec to make use of Overhead field. Add validation
and validation tests.

Signed-off-by: Eric Ernst <eric.ernst@intel.com>

pkg/apis/core/types.go

@@ -2700,6 +2700,16 @@ type PodSpec struct {
 	// This is a beta feature as of Kubernetes v1.14.
 	// +optional
 	RuntimeClassName *string
+	// Overhead represents the resource overhead associated with running a pod for a given RuntimeClass.
+	// This field will be autopopulated at admission time by the RuntimeClass admission controller. If
+	// the RuntimeClass admission controller is enabled, overhead must not be set in Pod create requests.
+	// The RuntimeClass admission controller will reject Pod create requests which have the overhead already
+	// set. If RuntimeClass is configured and selected in the PodSpec, Overhead will be set to the value
+	// defined in the corresponding RuntimeClass, otherwise it will remain unset and treated as zero.
+	// More info: https://git.k8s.io/enhancements/keps/sig-node/20190226-pod-overhead.md
+	// This field is alpha-level as of Kubernetes v1.16, and is only honored by servers that enable the PodOverhead feature.
+	// +optional
+	Overhead ResourceList
 	// EnableServiceLinks indicates whether information about services should be injected into pod's
 	// environment variables, matching the syntax of Docker links.
 	// If not specified, the default is true.

pkg/apis/core/validation/validation.go

@@ -264,6 +264,12 @@ func ValidateRuntimeClassName(name string, fldPath *field.Path) field.ErrorList
 	return allErrs
 }
 
+// validateOverhead can be used to check whether the given Overhead is valid.
+func validateOverhead(overhead core.ResourceList, fldPath *field.Path) field.ErrorList {
+	// reuse the ResourceRequirements validation logic
+	return ValidateResourceRequirements(&core.ResourceRequirements{Limits: overhead}, fldPath)
+}
+
 // Validates that given value is not negative.
 func ValidateNonnegativeField(value int64, fldPath *field.Path) field.ErrorList {
 	return apimachineryvalidation.ValidateNonnegativeField(value, fldPath)
@@ -3095,6 +3101,10 @@ func ValidatePodSpec(spec *core.PodSpec, fldPath *field.Path) field.ErrorList {
 		allErrs = append(allErrs, ValidatePreemptionPolicy(spec.PreemptionPolicy, fldPath.Child("preemptionPolicy"))...)
 	}
 
+	if spec.Overhead != nil && utilfeature.DefaultFeatureGate.Enabled(features.PodOverhead) {
+		allErrs = append(allErrs, validateOverhead(spec.Overhead, fldPath.Child("overhead"))...)
+	}
+
 	return allErrs
 }
 

pkg/apis/core/validation/validation_test.go

@@ -6334,6 +6334,7 @@ func TestValidatePodSpec(t *testing.T) {
 
 	defer featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, features.PodPriority, true)()
 	defer featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, features.RuntimeClass, true)()
+	defer featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, features.PodOverhead, true)()
 
 	successCases := []core.PodSpec{
 		{ // Populate basic fields, leave defaults for most.
@@ -6474,6 +6475,13 @@ func TestValidatePodSpec(t *testing.T) {
 			DNSPolicy:        core.DNSClusterFirst,
 			RuntimeClassName: utilpointer.StringPtr("valid-sandbox"),
 		},
+		{ // Populate Overhead
+			Containers:       []core.Container{{Name: "ctr", Image: "image", ImagePullPolicy: "IfNotPresent", TerminationMessagePolicy: "File"}},
+			RestartPolicy:    core.RestartPolicyAlways,
+			DNSPolicy:        core.DNSClusterFirst,
+			RuntimeClassName: utilpointer.StringPtr("valid-sandbox"),
+			Overhead:         core.ResourceList{},
+		},
 	}
 	for i := range successCases {
 		if errs := ValidatePodSpec(&successCases[i], field.NewPath("field")); len(errs) != 0 {
@@ -13498,3 +13506,42 @@ func TestAlphaVolumePVCDataSource(t *testing.T) {
 		}
 	}
 }
+
+func TestValidateOverhead(t *testing.T) {
+	defer featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, features.PodOverhead, true)()
+
+	successCase := []struct {
+		Name     string
+		overhead core.ResourceList
+	}{
+		{
+			Name: "Valid Overhead for CPU + Memory",
+			overhead: core.ResourceList{
+				core.ResourceName(core.ResourceCPU):    resource.MustParse("10"),
+				core.ResourceName(core.ResourceMemory): resource.MustParse("10G"),
+			},
+		},
+	}
+	for _, tc := range successCase {
+		if errs := validateOverhead(tc.overhead, field.NewPath("overheads")); len(errs) != 0 {
+			t.Errorf("%q unexpected error: %v", tc.Name, errs)
+		}
+	}
+
+	errorCase := []struct {
+		Name     string
+		overhead core.ResourceList
+	}{
+		{
+			Name: "Invalid Overhead Resources",
+			overhead: core.ResourceList{
+				core.ResourceName("my.org"): resource.MustParse("10m"),
+			},
+		},
+	}
+	for _, tc := range errorCase {
+		if errs := validateOverhead(tc.overhead, field.NewPath("resources")); len(errs) == 0 {
+			t.Errorf("%q expected error", tc.Name)
+		}
+	}
+}