Add PriorityClass support for pod scheduling and preemption

api/v1/runtimecomponent_types.go

@@ -168,6 +168,10 @@ type RuntimeComponentSpec struct {
 	// The list of hostnames and IPs that will be injected into the application pod's hosts file
 	// +operator-sdk:csv:customresourcedefinitions:order=30,type=spec,displayName="Host Aliases"
 	HostAliases []corev1.HostAlias `json:"hostAliases,omitempty"`
+
+	// Name of the PriorityClass for the pod.
+	// +operator-sdk:csv:customresourcedefinitions:order=31,type=spec,displayName="Priority Class Name"
+	PriorityClassName *string `json:"priorityClassName,omitempty"`
 }
 
 // Defines the DNS
@@ -1107,6 +1111,10 @@ func (cr *RuntimeComponent) GetHostAliases() []corev1.HostAlias {
 	return cr.Spec.HostAliases
 }
 
+func (cr *RuntimeComponent) GetPriorityClassName() *string {
+	return cr.Spec.PriorityClassName
+}
+
 // Initialize the RuntimeComponent instance
 func (cr *RuntimeComponent) Initialize() {
 	if cr.Spec.PullPolicy == nil {

bundle/manifests/rc.app.stacks_runtimecomponents.yaml

@@ -4590,6 +4590,9 @@ spec:
                       is allowed from.
                     type: object
                 type: object
+              priorityClassName:
+                description: Name of the PriorityClass for the pod.
+                type: string
               probes:
                 description: Define health checks on application container to determine
                   whether it is alive or ready to receive traffic

bundle/manifests/runtime-component.clusterserviceversion.yaml

@@ -422,6 +422,11 @@ spec:
           application pod's hosts file
         displayName: Host Aliases
         path: hostAliases
+      - description: Name of the PriorityClass for the pod.
+        displayName: Priority Class Name
+        path: priorityClassName
+        x-descriptors:
+        - urn:alm:descriptor:com.tectonic.ui:text
       - description: Labels to set on ServiceMonitor.
         displayName: Monitoring Labels
         path: monitoring.labels

common/types.go

@@ -264,4 +264,5 @@ type BaseComponent interface {
 	GetDNS() BaseComponentDNS
 	GetDisableTopologyRouting() *bool
 	GetHostAliases() []corev1.HostAlias
+	GetPriorityClassName() *string
 }

config/crd/bases/rc.app.stacks_runtimecomponents.yaml

@@ -4586,6 +4586,9 @@ spec:
                       is allowed from.
                     type: object
                 type: object
+              priorityClassName:
+                description: Name of the PriorityClass for the pod.
+                type: string
               probes:
                 description: Define health checks on application container to determine
                   whether it is alive or ready to receive traffic

config/manifests/bases/runtime-component.clusterserviceversion.yaml

@@ -367,6 +367,9 @@ spec:
         path: monitoring.endpoints
         x-descriptors:
         - urn:alm:descriptor:com.tectonic.ui:endpointList
+      - description: Name of the PriorityClass for the pod.
+        displayName: Priority Class Name
+        path: priorityClassName
       - description: Tolerations to be added to application pods. Tolerations allow
           the scheduler to schedule pods on nodes with matching taints.
         displayName: Tolerations

doc/user-guide-v1.adoc

@@ -152,6 +152,7 @@ Each `RuntimeComponent` CR must at least specify the `.spec.applicationImage` fi
 | `networkPolicy.disable` | A Boolean to disable the creation of the network policy. The default value is `false`. By default, network policies for an application are created and limit incoming traffic.
 | `networkPolicy.fromLabels` | The labels of one or more pods from which incoming traffic is allowed.
 | `networkPolicy.namespaceLabels` | The labels of namespaces from which incoming traffic is allowed.
+| `priorityClassName` | The name of the PriorityClass to assign to the application pod. PriorityClasses define the scheduling priority and preemption behaviour of pods. For examples, see link:++https://kubernetes.io/docs/concepts/scheduling-eviction/pod-priority-preemption/++[Pod Priority and Preemption].
 | `probes` | Defines health checks on an application container to determine whether it is alive or ready to receive traffic. For examples, see link:++https://github.com/OpenLiberty/open-liberty-operator/blob/main/doc/user-guide-v1.adoc#configure-probes++[Configure probes].
 | `probes.liveness` | A YAML object configuring the link:++https://kubernetes.io/docs/tasks/configure-pod-container/configure-liveness-readiness-startup-probes/#define-a-liveness-http-request++[Kubernetes liveness probe] that controls when Kubernetes needs to restart the pod.
 | `probes.readiness`   | A YAML object configuring the link:++https://kubernetes.io/docs/tasks/configure-pod-container/configure-liveness-readiness-startup-probes/#define-readiness-probes++[Kubernetes readiness probe] that controls when the pod is ready to receive traffic.

examples/priorityclass/01-priorityclass.yaml

@@ -0,0 +1,7 @@
+apiVersion: scheduling.k8s.io/v1
+kind: PriorityClass
+metadata:
+  name: service-critical
+value: 1000000
+globalDefault: false
+description: "Reserved for critical workloads. Pods with this class may preempt lower-priority pods during resource contention. Pods are Priority 0 by default."

examples/priorityclass/02-runtimecomponent.yaml

@@ -0,0 +1,42 @@
+apiVersion: rc.app.stacks/v1
+kind: RuntimeComponent
+metadata:
+  name: payment-service
+spec:
+  applicationImage: icr.io/appcafe/open-liberty/samples/getting-started@sha256:80a28b6a71ec02369cc13f621e4c3cca0d63b1977be76e15dabbfba48411107f
+  manageTLS: true
+  resources:
+    limits:
+      cpu: 500m
+      memory: 1Gi
+    requests:
+      cpu: 200m
+      memory: 512Mi
+  replicas: 2
+  priorityClassName: service-critical
+  service:
+    port: 9443
+  serviceAccount:
+    mountToken: true
+  probes:
+    startup:
+      failureThreshold: 12
+      periodSeconds: 5
+      httpGet:
+        path: /health/started
+        port: 9443
+    readiness:
+      httpGet:
+        path: /health/ready
+        port: 9443
+      initialDelaySeconds: 1
+      periodSeconds: 5
+      failureThreshold: 24
+    liveness:
+      httpGet:
+        path: /health/live
+        port: 9443
+      initialDelaySeconds: 8
+      periodSeconds: 5
+
+

internal/deploy/kubectl/runtime-component-crd.yaml

@@ -4589,6 +4589,9 @@ spec:
                       is allowed from.
                     type: object
                 type: object
+              priorityClassName:
+                description: Name of the PriorityClass for the pod.
+                type: string
               probes:
                 description: Define health checks on application container to determine
                   whether it is alive or ready to receive traffic

internal/deploy/kustomize/daily/base/runtime-component-crd.yaml

@@ -4589,6 +4589,9 @@ spec:
                       is allowed from.
                     type: object
                 type: object
+              priorityClassName:
+                description: Name of the PriorityClass for the pod.
+                type: string
               probes:
                 description: Define health checks on application container to determine
                   whether it is alive or ready to receive traffic

utils/utils.go

@@ -765,6 +765,11 @@ func CustomizePodSpec(pts *corev1.PodTemplateSpec, ba common.BaseComponent) {
 	}
 
 	pts.Spec.Tolerations = ba.GetTolerations()
+
+	pts.Spec.PriorityClassName = ""
+	if ba.GetPriorityClassName() != nil {
+		pts.Spec.PriorityClassName = *ba.GetPriorityClassName()
+	}
 }
 
 // Initialize an empty TopologySpreadConstraints list and optionally prefers scheduling across zones/hosts for pods with podMatchLabels
@@ -1012,6 +1017,11 @@ func CustomizeKnativeService(ksvc *servingv1.Service, ba common.BaseComponent) {
 	} else {
 		ksvc.Spec.Template.Spec.AutomountServiceAccountToken = nil
 	}
+
+	ksvc.Spec.Template.Spec.PriorityClassName = ""
+	if ba.GetPriorityClassName() != nil {
+		ksvc.Spec.Template.Spec.PriorityClassName = *ba.GetPriorityClassName()
+	}
 }
 
 // CustomizeHPA for autoscaling/v2

utils/utils_test.go

@@ -494,6 +494,40 @@ func TestCustomizePodSpecServiceLinks(t *testing.T) {
 	verifyTests(testCPS, t)
 }
 
+func TestCustomizePodSpecPriorityClassName(t *testing.T) {
+	logger := zap.New()
+	logf.SetLogger(logger)
+
+	spec := appstacksv1.RuntimeComponentSpec{
+		ApplicationImage: appImage,
+		Service:          service,
+	}
+
+	pts, runtime := &corev1.PodTemplateSpec{}, createRuntimeComponent(name, namespace, spec)
+	CustomizePodSpec(pts, runtime)
+	defaultPriorityClassName := pts.Spec.PriorityClassName
+
+	priorityClassName := "high-priority"
+	spec.PriorityClassName = &priorityClassName
+	pts, runtime = &corev1.PodTemplateSpec{}, createRuntimeComponent(name, namespace, spec)
+	CustomizePodSpec(pts, runtime)
+	setPriorityClassName := pts.Spec.PriorityClassName
+
+	spec.PriorityClassName = nil
+	pts = &corev1.PodTemplateSpec{}
+	pts.Spec.PriorityClassName = priorityClassName
+	runtime = createRuntimeComponent(name, namespace, spec)
+	CustomizePodSpec(pts, runtime)
+	clearPriorityClassName := pts.Spec.PriorityClassName
+
+	testCPS := []Test{
+		{"Default PriorityClassName (not set)", "", defaultPriorityClassName},
+		{"Set PriorityClassName", priorityClassName, setPriorityClassName},
+		{"Clearing PriorityClassName", "", clearPriorityClassName},
+	}
+	verifyTests(testCPS, t)
+}
+
 func TestCustomizePersistence(t *testing.T) {
 	logger := zap.New()
 	logf.SetLogger(logger)