Add support for the pod runtimeclass

**What**
- Allow policies to configure the Pod RunTimeClassName

Signed-off-by: Lucas Roesler <roesler.lucas@gmail.com>

k8s/policies.go

@@ -26,8 +26,23 @@ type PolicyClient interface {
 // to functions by annotating them with `com.openfaas/policy: name1,name2`
 type Policy struct {
 	// If specified, the function's pod tolerations.
+	//
+	// copied to the Pod Tolerations
+	//
 	// +optional
 	Tolerations []corev1.Toleration `json:"tolerations,omitempty"`
+
+	// RuntimeClassName refers to a RuntimeClass object in the node.k8s.io group, which should be used
+	// to run this pod.  If no RuntimeClass resource matches the named class, the pod will not be run.
+	// If unset or empty, the "legacy" RuntimeClass will be used, which is an implicit class with an
+	// empty definition that uses the default runtime handler.
+	// More info: https://git.k8s.io/enhancements/keps/sig-node/runtime-class.md
+	// This is a beta feature as of Kubernetes v1.14.
+	//
+	// copied to the Pod RunTimeClass
+	//
+	// +optional
+	RuntimeClassName *string `json:"runtimeClassName,omitempty"`
 }
 
 // Apply adds or mutates the configuration of the Deployment with the values defined
@@ -37,6 +52,11 @@ func (p Policy) Apply(deployment *appsv1.Deployment) *appsv1.Deployment {
 	if len(p.Tolerations) > 0 {
 		deployment.Spec.Template.Spec.Tolerations = append(deployment.Spec.Template.Spec.Tolerations, p.Tolerations...)
 	}
+
+	if p.RuntimeClassName != nil {
+		deployment.Spec.Template.Spec.RuntimeClassName = p.RuntimeClassName
+	}
+
 	return deployment
 }
 
@@ -56,9 +76,32 @@ func (p Policy) Remove(deployment *appsv1.Deployment) *appsv1.Deployment {
 		deployment.Spec.Template.Spec.Tolerations = newTolerations
 	}
 
+	if p.RuntimeClassName != nil {
+		if equalStrings(deployment.Spec.Template.Spec.RuntimeClassName, p.RuntimeClassName) {
+			deployment.Spec.Template.Spec.RuntimeClassName = nil
+		}
+	}
+
 	return deployment
 }
 
+func equalStrings(a, b *string) bool {
+	if a == nil && b == nil {
+		return true
+	}
+
+	if a != nil && b == nil {
+		return false
+	}
+
+	if a == nil && b != nil {
+		return false
+	}
+
+	// now we know both values are non-nil
+	return *a == *b
+}
+
 type policyClient struct {
 	kube typedCorev1.ConfigMapsGetter
 }

k8s/policies_test.go

@@ -153,6 +153,83 @@ func Test_TolerationsPolicy_Apply(t *testing.T) {
 	}
 }
 
+func Test_RunTimeClassPolicy_Apply(t *testing.T) {
+	expectedClass := "fastRunTime"
+	p := Policy{RuntimeClassName: &expectedClass}
+
+	basicDeployment := &appsv1.Deployment{
+		Spec: appsv1.DeploymentSpec{
+			Template: apiv1.PodTemplateSpec{
+				Spec: apiv1.PodSpec{
+					Containers: []apiv1.Container{
+						{Name: "testfunc", Image: "alpine:latest"},
+					},
+				},
+			},
+		},
+	}
+
+	basicDeployment = p.Apply(basicDeployment)
+	result := basicDeployment.Spec.Template.Spec.RuntimeClassName
+	if result == nil {
+		t.Fatalf("expected %s, got nil", expectedClass)
+	}
+	if expectedClass != *result {
+		t.Fatalf("expected %s, got %v", expectedClass, *result)
+	}
+}
+
+func Test_RunTimeClaasPolicy_Remove(t *testing.T) {
+	t.Run("remove matching runtime class ", func(t *testing.T) {
+		expectedClass := "fastRunTime"
+		p := Policy{RuntimeClassName: &expectedClass}
+
+		basicDeployment := &appsv1.Deployment{
+			Spec: appsv1.DeploymentSpec{
+				Template: apiv1.PodTemplateSpec{
+					Spec: apiv1.PodSpec{
+						RuntimeClassName: &expectedClass,
+						Containers: []apiv1.Container{
+							{Name: "testfunc", Image: "alpine:latest"},
+						},
+					},
+				},
+			},
+		}
+
+		basicDeployment = p.Remove(basicDeployment)
+		result := basicDeployment.Spec.Template.Spec.RuntimeClassName
+		if result != nil {
+			t.Fatalf("expected nil, got %s", *result)
+		}
+	})
+
+	t.Run("leaves runtime class that does not match", func(t *testing.T) {
+		expectedClass := "fastRunTime"
+		policyClass := "slowRunTime"
+		p := Policy{RuntimeClassName: &policyClass}
+
+		basicDeployment := &appsv1.Deployment{
+			Spec: appsv1.DeploymentSpec{
+				Template: apiv1.PodTemplateSpec{
+					Spec: apiv1.PodSpec{
+						RuntimeClassName: &expectedClass,
+						Containers: []apiv1.Container{
+							{Name: "testfunc", Image: "alpine:latest"},
+						},
+					},
+				},
+			},
+		}
+
+		basicDeployment = p.Remove(basicDeployment)
+		result := basicDeployment.Spec.Template.Spec.RuntimeClassName
+		if !equalStrings(result, &expectedClass) {
+			t.Fatalf("expected %s, got %v", expectedClass, result)
+		}
+	})
+}
+
 func Test_TolerationsPolicy_Remove(t *testing.T) {
 	tolerations := []corev1.Toleration{
 		{