Add a predicate for persistent disk scheduling.

pkg/scheduler/predicates.go

@@ -51,6 +51,39 @@ func (nodes ClientNodeInfo) GetNodeInfo(nodeID string) (*api.Minion, error) {
 	return nodes.GetMinion(nodeID)
 }
 
+func isVolumeConflict(volume api.Volume, pod *api.Pod) bool {
+	if volume.Source.GCEPersistentDisk == nil {
+		return false
+	}
+	pdName := volume.Source.GCEPersistentDisk.PDName
+
+	manifest := &(pod.DesiredState.Manifest)
+	for ix := range manifest.Volumes {
+		if manifest.Volumes[ix].Source.GCEPersistentDisk != nil &&
+			manifest.Volumes[ix].Source.GCEPersistentDisk.PDName == pdName {
+			return true
+		}
+	}
+	return false
+}
+
+// NoDiskConflict evaluates if a pod can fit due to the volumes it requests, and those that
+// are already mounted. Some times of volumes are mounted onto node machines.  For now, these mounts
+// are exclusive so if there is already a volume mounted on that node, another pod can't schedule
+// there. This is GCE specific for now.
+// TODO: migrate this into some per-volume specific code?
+func NoDiskConflict(pod api.Pod, existingPods []api.Pod, node string) (bool, error) {
+	manifest := &(pod.DesiredState.Manifest)
+	for ix := range manifest.Volumes {
+		for podIx := range existingPods {
+			if isVolumeConflict(manifest.Volumes[ix], &existingPods[podIx]) {
+				return false, nil
+			}
+		}
+	}
+	return true, nil
+}
+
 type ResourceFit struct {
 	info NodeInfo
 }

pkg/scheduler/predicates_test.go

@@ -181,3 +181,56 @@ func TestPodFitsPorts(t *testing.T) {
 		}
 	}
 }
+
+func TestDiskConflicts(t *testing.T) {
+	volState := api.PodState{
+		Manifest: api.ContainerManifest{
+			Volumes: []api.Volume{
+				{
+					Source: &api.VolumeSource{
+						GCEPersistentDisk: &api.GCEPersistentDisk{
+							PDName: "foo",
+						},
+					},
+				},
+			},
+		},
+	}
+	volState2 := api.PodState{
+		Manifest: api.ContainerManifest{
+			Volumes: []api.Volume{
+				{
+					Source: &api.VolumeSource{
+						GCEPersistentDisk: &api.GCEPersistentDisk{
+							PDName: "bar",
+						},
+					},
+				},
+			},
+		},
+	}
+	tests := []struct {
+		pod          api.Pod
+		existingPods []api.Pod
+		isOk         bool
+		test         string
+	}{
+		{api.Pod{}, []api.Pod{}, true, "nothing"},
+		{api.Pod{}, []api.Pod{{DesiredState: volState}}, true, "one state"},
+		{api.Pod{DesiredState: volState}, []api.Pod{{DesiredState: volState}}, false, "same state"},
+		{api.Pod{DesiredState: volState2}, []api.Pod{{DesiredState: volState}}, true, "different state"},
+	}
+
+	for _, test := range tests {
+		ok, err := NoDiskConflict(test.pod, test.existingPods, "machine")
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if test.isOk && !ok {
+			t.Errorf("expected ok, got none.  %v %v %s", test.pod, test.existingPods, test.test)
+		}
+		if !test.isOk && ok {
+			t.Errorf("expected no ok, got one.  %v %v %s", test.pod, test.existingPods, test.test)
+		}
+	}
+}

plugin/pkg/scheduler/factory/factory.go

@@ -72,6 +72,8 @@ func (factory *ConfigFactory) Create() *scheduler.Config {
 			algorithm.PodFitsPorts,
 			// Fit is determined by resource availability
 			algorithm.NewResourceFitPredicate(minionLister),
+			// Fit is determined by non-conflicting disk volumes
+			algorithm.NoDiskConflict,
 		},
 		// Prioritize nodes by least requested utilization.
 		algorithm.LeastRequestedPriority,