Do not use transformer when fqdnTemplate is set

source/pod.go

@@ -78,9 +78,11 @@ func NewPodSource(
 
 	_, _ = podInformer.Informer().AddEventHandler(informers.DefaultEventHandler())
 
+	if fqdnTemplate == "" {
 		// Transformer is used to reduce the memory usage of the informer.
 		// The pod informer will otherwise store a full in-memory, go-typed copy of all pod schemas in the cluster.
 		// If watchList is not used it will not prevent memory bursts on the initial informer sync.
+		// When fqdnTemplate is used the entire pod needs to be provided to the rendering call, but the informer itself becomes unneeded.
 		podInformer.Informer().SetTransform(func(i interface{}) (interface{}, error) {
 			pod, ok := i.(*corev1.Pod)
 			if !ok {
@@ -107,6 +109,8 @@ func NewPodSource(
 				},
 			}, nil
 		})
+	}
+
 	_, _ = nodeInformer.Informer().AddEventHandler(informers.DefaultEventHandler())
 
 	informerFactory.Start(ctx.Done())

source/pod_test.go

@@ -1000,6 +1000,7 @@ func nodesFixturesIPv4() []*corev1.Node {
 }
 
 func TestPodTransformerInPodSource(t *testing.T) {
+	t.Run("transformer set", func(t *testing.T) {
 		ctx := t.Context()
 		fakeClient := fake.NewClientset()
 
@@ -1078,4 +1079,66 @@ func TestPodTransformerInPodSource(t *testing.T) {
 		assert.Empty(t, retrieved.Status.HostIP)
 		assert.Equal(t, "127.0.0.1", retrieved.Status.PodIP)
 		assert.Empty(t, retrieved.Status.Conditions)
+	})
+
+	t.Run("transormer is not used when fqdnTemplate is set", func(t *testing.T) {
+		ctx := t.Context()
+		fakeClient := fake.NewClientset()
+
+		pod := &v1.Pod{
+			Spec: v1.PodSpec{
+				Containers: []v1.Container{{
+					Name: "test",
+				}},
+				Hostname:    "test-hostname",
+				NodeName:    "test-node",
+				HostNetwork: true,
+			},
+			ObjectMeta: metav1.ObjectMeta{
+				Namespace: "test-ns",
+				Name:      "test-name",
+				Labels: map[string]string{
+					"label1": "value1",
+					"label2": "value2",
+					"label3": "value3",
+				},
+				Annotations: map[string]string{
+					"user-annotation": "value",
+					"external-dns.alpha.kubernetes.io/hostname": "test-hostname",
+					"external-dns.alpha.kubernetes.io/random":   "value",
+					"other/annotation":                          "value",
+				},
+				UID: "someuid",
+			},
+			Status: v1.PodStatus{
+				PodIP:  "127.0.0.1",
+				HostIP: "127.0.0.2",
+				Conditions: []v1.PodCondition{{
+					Type:   v1.PodReady,
+					Status: v1.ConditionTrue,
+				}, {
+					Type:   v1.ContainersReady,
+					Status: v1.ConditionFalse,
+				}},
+			},
+		}
+
+		_, err := fakeClient.CoreV1().Pods(pod.Namespace).Create(context.Background(), pod, metav1.CreateOptions{})
+		require.NoError(t, err)
+
+		// Should not error when creating the source
+		src, err := NewPodSource(ctx, fakeClient, "", "", false, "", "template", false, "", nil)
+		require.NoError(t, err)
+		ps, ok := src.(*podSource)
+		require.True(t, ok)
+
+		retrieved, err := ps.podInformer.Lister().Pods("test-ns").Get("test-name")
+		require.NoError(t, err)
+
+		// Metadata
+		assert.Equal(t, "test-name", retrieved.Name)
+		assert.Equal(t, "test-ns", retrieved.Namespace)
+		assert.NotEmpty(t, retrieved.UID)
+		assert.NotEmpty(t, retrieved.Labels)
+	})
 }