simplify disruption controller

pkg/controller/disruption/disruption.go

@@ -107,7 +107,7 @@ type controllerAndScale struct {
 
 // podControllerFinder is a function type that maps a pod to a list of
 // controllers and their scale.
-type podControllerFinder func(*v1.Pod) ([]controllerAndScale, error)
+type podControllerFinder func(*v1.Pod) (*controllerAndScale, error)
 
 func NewDisruptionController(
 	podInformer coreinformers.PodInformer,
@@ -170,8 +170,8 @@ func NewDisruptionController(
 // and we may well need further tweaks just to be able to access scale
 // subresources.
 func (dc *DisruptionController) finders() []podControllerFinder {
-	return []podControllerFinder{dc.getPodReplicationControllers, dc.getPodDeployments, dc.getPodReplicaSets,
-		dc.getPodStatefulSets}
+	return []podControllerFinder{dc.getPodReplicationController, dc.getPodDeployment, dc.getPodReplicaSet,
+		dc.getPodStatefulSet}
 }
 
 var (
@@ -181,9 +181,8 @@ var (
 	controllerKindDep = v1beta1.SchemeGroupVersion.WithKind("Deployment")
 )
 
-// getPodReplicaSets finds replicasets which have no matching deployments.
-func (dc *DisruptionController) getPodReplicaSets(pod *v1.Pod) ([]controllerAndScale, error) {
-	var casSlice []controllerAndScale
+// getPodReplicaSet finds a replicaset which has no matching deployments.
+func (dc *DisruptionController) getPodReplicaSet(pod *v1.Pod) (*controllerAndScale, error) {
 	controllerRef := metav1.GetControllerOf(pod)
 	if controllerRef == nil {
 		return nil, nil
@@ -204,13 +203,11 @@ func (dc *DisruptionController) getPodReplicaSets(pod *v1.Pod) ([]controllerAndS
 		// Skip RS if it's controlled by a Deployment.
 		return nil, nil
 	}
-	casSlice = append(casSlice, controllerAndScale{rs.UID, *(rs.Spec.Replicas)})
-	return casSlice, nil
+	return &controllerAndScale{rs.UID, *(rs.Spec.Replicas)}, nil
 }
 
 // getPodStatefulSet returns the statefulset managing the given pod.
-func (dc *DisruptionController) getPodStatefulSets(pod *v1.Pod) ([]controllerAndScale, error) {
-	var casSlice []controllerAndScale
+func (dc *DisruptionController) getPodStatefulSet(pod *v1.Pod) (*controllerAndScale, error) {
 	controllerRef := metav1.GetControllerOf(pod)
 	if controllerRef == nil {
 		return nil, nil
@@ -227,13 +224,11 @@ func (dc *DisruptionController) getPodStatefulSets(pod *v1.Pod) ([]controllerAnd
 		return nil, nil
 	}
 
-	casSlice = append(casSlice, controllerAndScale{ss.UID, *(ss.Spec.Replicas)})
-	return casSlice, nil
+	return &controllerAndScale{ss.UID, *(ss.Spec.Replicas)}, nil
 }
 
 // getPodDeployments finds deployments for any replicasets which are being managed by deployments.
-func (dc *DisruptionController) getPodDeployments(pod *v1.Pod) ([]controllerAndScale, error) {
-	var casSlice []controllerAndScale
+func (dc *DisruptionController) getPodDeployment(pod *v1.Pod) (*controllerAndScale, error) {
 	controllerRef := metav1.GetControllerOf(pod)
 	if controllerRef == nil {
 		return nil, nil
@@ -264,12 +259,10 @@ func (dc *DisruptionController) getPodDeployments(pod *v1.Pod) ([]controllerAndS
 	if deployment.UID != controllerRef.UID {
 		return nil, nil
 	}
-	casSlice = append(casSlice, controllerAndScale{deployment.UID, *(deployment.Spec.Replicas)})
-	return casSlice, nil
+	return &controllerAndScale{deployment.UID, *(deployment.Spec.Replicas)}, nil
 }
 
-func (dc *DisruptionController) getPodReplicationControllers(pod *v1.Pod) ([]controllerAndScale, error) {
-	var casSlice []controllerAndScale
+func (dc *DisruptionController) getPodReplicationController(pod *v1.Pod) (*controllerAndScale, error) {
 	controllerRef := metav1.GetControllerOf(pod)
 	if controllerRef == nil {
 		return nil, nil
@@ -285,8 +278,7 @@ func (dc *DisruptionController) getPodReplicationControllers(pod *v1.Pod) ([]con
 	if rc.UID != controllerRef.UID {
 		return nil, nil
 	}
-	casSlice = append(casSlice, controllerAndScale{rc.UID, *(rc.Spec.Replicas)})
-	return casSlice, nil
+	return &controllerAndScale{rc.UID, *(rc.Spec.Replicas)}, nil
 }
 
 func (dc *DisruptionController) Run(stopCh <-chan struct{}) {
@@ -590,30 +582,26 @@ func (dc *DisruptionController) getExpectedScale(pdb *policy.PodDisruptionBudget
 	// A mapping from controllers to their scale.
 	controllerScale := map[types.UID]int32{}
 
-	// 1. Find the controller(s) for each pod.  If any pod has 0 controllers,
-	// that's an error.  If any pod has more than 1 controller, that's also an
-	// error.
+	// 1. Find the controller for each pod.  If any pod has 0 controllers,
+	// that's an error. With ControllerRef, a pod can only have 1 controller.
 	for _, pod := range pods {
-		controllerCount := 0
+		foundController := false
 		for _, finder := range dc.finders() {
-			var controllers []controllerAndScale
-			controllers, err = finder(pod)
+			var controllerNScale *controllerAndScale
+			controllerNScale, err = finder(pod)
 			if err != nil {
 				return
 			}
-			for _, controller := range controllers {
-				controllerScale[controller.UID] = controller.scale
-				controllerCount++
+			if controllerNScale != nil {
+				controllerScale[controllerNScale.UID] = controllerNScale.scale
+				foundController = true
+				break
 			}
 		}
-		if controllerCount == 0 {
+		if !foundController {
 			err = fmt.Errorf("found no controllers for pod %q", pod.Name)
 			dc.recorder.Event(pdb, v1.EventTypeWarning, "NoControllers", err.Error())
 			return
-		} else if controllerCount > 1 {
-			err = fmt.Errorf("pod %q has %v>1 controllers", pod.Name, controllerCount)
-			dc.recorder.Event(pdb, v1.EventTypeWarning, "TooManyControllers", err.Error())
-			return
 		}
 	}