Merge pull request #2197 from claire921/scheduler

Refactor selectHost in Sched

pkg/scheduler/generic_scheduler.go

@@ -53,6 +53,9 @@ func (g *genericScheduler) Schedule(pod api.Pod, minionLister MinionLister) (str
 }
 
 func (g *genericScheduler) selectHost(priorityList HostPriorityList) (string, error) {
+	if len(priorityList) == 0 {
+		return "", fmt.Errorf("empty priorityList")
+	}
 	sort.Sort(priorityList)
 
 	hosts := getMinHosts(priorityList)

pkg/scheduler/generic_scheduler_test.go

@@ -23,6 +23,7 @@ import (
 	"testing"
 
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/util"
 )
 
 func falsePredicate(pod api.Pod, existingPods []api.Pod, node string) (bool, error) {
@@ -68,6 +69,72 @@ func makeMinionList(nodeNames []string) api.MinionList {
 	return result
 }
 
+func TestSelectHost(t *testing.T) {
+	scheduler := genericScheduler{random: rand.New(rand.NewSource(0))}
+	tests := []struct {
+		list          HostPriorityList
+		possibleHosts util.StringSet
+		expectsErr    bool
+	}{
+		{
+			list: []HostPriority{
+				{host: "machine1.1", score: 1},
+				{host: "machine2.1", score: 2},
+			},
+			possibleHosts: util.NewStringSet("machine1.1"),
+			expectsErr:    false,
+		},
+		// equal scores
+		{
+			list: []HostPriority{
+				{host: "machine1.1", score: 1},
+				{host: "machine1.2", score: 1},
+				{host: "machine1.3", score: 1},
+				{host: "machine2.1", score: 2},
+			},
+			possibleHosts: util.NewStringSet("machine1.1", "machine1.2", "machine1.3"),
+			expectsErr:    false,
+		},
+		// out of order scores
+		{
+			list: []HostPriority{
+				{host: "machine1.1", score: 1},
+				{host: "machine1.2", score: 1},
+				{host: "machine2.1", score: 2},
+				{host: "machine3.1", score: 3},
+				{host: "machine1.3", score: 1},
+			},
+			possibleHosts: util.NewStringSet("machine1.1", "machine1.2", "machine1.3"),
+			expectsErr:    false,
+		},
+		// empty priorityList
+		{
+			list:          []HostPriority{},
+			possibleHosts: util.NewStringSet(),
+			expectsErr:    true,
+		},
+	}
+
+	for _, test := range tests {
+		// increase the randomness
+		for i := 0; i < 10; i++ {
+			got, err := scheduler.selectHost(test.list)
+			if test.expectsErr {
+				if err == nil {
+					t.Error("Unexpected non-error")
+				}
+			} else {
+				if err != nil {
+					t.Errorf("Unexpected error: %v", err)
+				}
+				if !test.possibleHosts.Has(got) {
+					t.Errorf("got %s is not in the possible map %v", got, test.possibleHosts)
+				}
+			}
+		}
+	}
+}
+
 func TestGenericScheduler(t *testing.T) {
 	tests := []struct {
 		predicates   []FitPredicate