Merge pull request #1731 from prometheus/release-0.19

Forward-merge 0.19 fixes to master

retrieval/discovery/marathon/marathon.go

@@ -216,6 +216,9 @@ func createTargetGroup(app *App) *config.TargetGroup {
 func targetsForApp(app *App) []model.LabelSet {
 	targets := make([]model.LabelSet, 0, len(app.Tasks))
 	for _, t := range app.Tasks {
+		if len(t.Ports) == 0 {
+			continue
+		}
 		target := targetForTask(&t)
 		targets = append(targets, model.LabelSet{
 			model.AddressLabel: model.LabelValue(target),

retrieval/discovery/marathon/marathon_test.go

@@ -175,3 +175,49 @@ func TestMarathonSDRunAndStop(t *testing.T) {
 		t.Fatalf("Channel not closed.")
 	}
 }
+
+func marathonTestZeroTaskPortAppList(labels map[string]string, runningTasks int) *AppList {
+	task := Task{
+		ID:    "test-task-2",
+		Host:  "mesos-slave-2",
+		Ports: []uint32{},
+	}
+	docker := DockerContainer{Image: "repo/image:tag"}
+	container := Container{Docker: docker}
+	app := App{
+		ID:           "test-service-zero-ports",
+		Tasks:        []Task{task},
+		RunningTasks: runningTasks,
+		Labels:       labels,
+		Container:    container,
+	}
+	return &AppList{
+		Apps: []App{app},
+	}
+}
+
+func TestMarathonZeroTaskPorts(t *testing.T) {
+	ch, md := newTestDiscovery(func(url string) (*AppList, error) {
+		return marathonTestZeroTaskPortAppList(marathonValidLabel, 1), nil
+	})
+
+	go func() {
+		select {
+		case tgs := <-ch:
+			tg := tgs[0]
+
+			if tg.Source != "test-service-zero-ports" {
+				t.Fatalf("Wrong target group name: %s", tg.Source)
+			}
+			if len(tg.Targets) != 0 {
+				t.Fatalf("Wrong number of targets: %v", tg.Targets)
+			}
+		default:
+			t.Fatal("Did not get a target group.")
+		}
+	}()
+	err := md.updateServices(context.Background(), ch)
+	if err != nil {
+		t.Fatalf("Got error: %s", err)
+	}
+}