Enhancements to scheduler priority functions

- Modified the existing spreading priority to consider service pods explicitly
 - Added a new priority function to spread pods across zones

pkg/scheduler/spreading.go

@@ -17,28 +17,44 @@ limitations under the License.
 package scheduler
 
 import (
-	"math/rand"
-
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/labels"
 )
 
+type ServiceSpread struct {
+	serviceLister ServiceLister
+}
+
+func NewServiceSpreadPriority(serviceLister ServiceLister) PriorityFunction {
+	serviceSpread := &ServiceSpread{
+		serviceLister: serviceLister,
+	}
+	return serviceSpread.CalculateSpreadPriority
+}
+
 // CalculateSpreadPriority spreads pods by minimizing the number of pods on the same machine with the same labels.
 // Importantly, if there are services in the system that span multiple heterogenous sets of pods, this spreading priority
 // may not provide optimal spreading for the members of that Service.
 // TODO: consider if we want to include Service label sets in the scheduling priority.
-func CalculateSpreadPriority(pod api.Pod, podLister PodLister, minionLister MinionLister) (HostPriorityList, error) {
-	pods, err := podLister.List(labels.SelectorFromSet(pod.Labels))
-	if err != nil {
-		return nil, err
+func (s *ServiceSpread) CalculateSpreadPriority(pod api.Pod, podLister PodLister, minionLister MinionLister) (HostPriorityList, error) {
+	var maxCount int
+	var pods []api.Pod
+	var err error
+
+	service, err := s.serviceLister.GetPodService(pod)
+	if err == nil {
+		selector := labels.SelectorFromSet(service.Spec.Selector)
+		pods, err = podLister.ListPods(selector)
+		if err != nil {
+			return nil, err
+		}
 	}
+
 	minions, err := minionLister.List()
 	if err != nil {
 		return nil, err
 	}
 
-	var maxCount int
-	var fScore float32 = 10.0
 	counts := map[string]int{}
 	if len(pods) > 0 {
 		for _, pod := range pods {
@@ -54,6 +70,8 @@ func CalculateSpreadPriority(pod api.Pod, podLister PodLister, minionLister Mini
 	//score int - scale of 0-10
 	// 0 being the lowest priority and 10 being the highest
 	for _, minion := range minions.Items {
+		// initializing to the default/max minion score of 10
+		fScore := float32(10)
 		if maxCount > 0 {
 			fScore = 10 * (float32(maxCount-counts[minion.Name]) / float32(maxCount))
 		}
@@ -62,6 +80,77 @@ func CalculateSpreadPriority(pod api.Pod, podLister PodLister, minionLister Mini
 	return result, nil
 }
 
-func NewSpreadingScheduler(podLister PodLister, minionLister MinionLister, predicates []FitPredicate, random *rand.Rand) Scheduler {
-	return NewGenericScheduler(predicates, []PriorityConfig{{Function: CalculateSpreadPriority, Weight: 1}}, podLister, random)
+type ZoneSpread struct {
+	serviceLister ServiceLister
+	zoneLabel     string
+}
+
+func NewZoneSpreadPriority(serviceLister ServiceLister, zoneLabel string) PriorityFunction {
+	zoneSpread := &ZoneSpread{
+		serviceLister: serviceLister,
+		zoneLabel:     zoneLabel,
+	}
+	return zoneSpread.ZoneSpreadPriority
+}
+
+func (z *ZoneSpread) ZoneSpreadPriority(pod api.Pod, podLister PodLister, minionLister MinionLister) (HostPriorityList, error) {
+	var service api.Service
+	var pods []api.Pod
+	var err error
+
+	service, err = z.serviceLister.GetPodService(pod)
+	if err == nil {
+		selector := labels.SelectorFromSet(service.Spec.Selector)
+		pods, err = podLister.ListPods(selector)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	minions, err := minionLister.List()
+	if err != nil {
+		return nil, err
+	}
+
+	// find the zones that the minions belong to
+	openMinions := []string{}
+	zonedMinions := map[string]string{}
+	for _, minion := range minions.Items {
+		if labels.Set(minion.Labels).Has(z.zoneLabel) {
+			zone := labels.Set(minion.Labels).Get(z.zoneLabel)
+			zonedMinions[minion.Name] = zone
+		} else {
+			openMinions = append(openMinions, minion.Name)
+		}
+	}
+
+	podCounts := map[string]int{}
+	numServicePods := len(pods)
+	if numServicePods > 0 {
+		for _, pod := range pods {
+			zone, exists := zonedMinions[pod.Status.Host]
+			if !exists {
+				continue
+			}
+			podCounts[zone]++
+		}
+	}
+
+	result := []HostPriority{}
+	//score int - scale of 0-10
+	// 0 being the lowest priority and 10 being the highest
+	for minion := range zonedMinions {
+		// initializing to the default/max minion score of 10
+		fScore := float32(10)
+		if numServicePods > 0 {
+			fScore = 10 * (float32(numServicePods-podCounts[zonedMinions[minion]]) / float32(numServicePods))
+		}
+		result = append(result, HostPriority{host: minion, score: int(fScore)})
+	}
+	// add the open minions with a score of 0
+	for _, minion := range openMinions {
+		result = append(result, HostPriority{host: minion, score: 0})
+	}
+
+	return result, nil
 }