Tighten pod resource attribution in the Stackdriver event sink

When mapping a corev1.Event onto a Stackdriver MonitoredResource with
InvolvedObject.Kind == "Pod", only emit a k8s_pod resource when the
event's own metadata.namespace is set and equals
event.InvolvedObject.Namespace. Use event.Namespace (the value the API
server validates against RBAC at event creation time) to populate the
namespace_name label. Events that fail the check fall back to the
default cluster-scoped resource so the log content is still exported.

Node attribution is intentionally unchanged in this PR; it will be
addressed separately.

Updates the existing pod test to populate event.Namespace and adds
cases that cover the new fallback paths.

Author: erain

event-exporter/sinks/stackdriver/log_entry_factory_test.go

@@ -111,6 +111,7 @@ func TestFromEvent(t *testing.T) {
 		{
 			desc: "k8s pod event with pod labels",
 			event: &corev1.Event{
+				ObjectMeta:     metav1.ObjectMeta{Namespace: "test_namespace"},
 				Type:           "Normal",
 				InvolvedObject: involvedPodObject,
 				LastTimestamp:  lastTimestamp,

event-exporter/sinks/stackdriver/monitored_resource_factory.go

@@ -74,7 +74,15 @@ func (f *monitoredResourceFactory) resourceFromEvent(event *corev1.Event) *sd.Mo
 
 	switch event.InvolvedObject.Kind {
 	case pod:
-		monitoredResource = f.buildPodMonitoredResource(event)
+		// The event's own metadata.namespace is the RBAC-enforced source
+		// of truth for where the event was created. Only emit a pod-scoped
+		// resource when the involved object's namespace agrees with it;
+		// otherwise fall back to the default cluster-scoped resource.
+		if event.Namespace != "" && event.Namespace == event.InvolvedObject.Namespace {
+			monitoredResource = f.buildPodMonitoredResource(event)
+		} else {
+			monitoredResource = f.defaultResource
+		}
 	case node:
 		monitoredResource = f.buildNodeMonitoredResource(event)
 	default:
@@ -86,7 +94,7 @@ func (f *monitoredResourceFactory) resourceFromEvent(event *corev1.Event) *sd.Mo
 func (f *monitoredResourceFactory) buildPodMonitoredResource(event *corev1.Event) *sd.MonitoredResource {
 	labels := copyMap(f.commonLabels)
 	labels[podName] = event.InvolvedObject.Name
-	labels[namespaceName] = event.InvolvedObject.Namespace
+	labels[namespaceName] = event.Namespace
 
 	return &sd.MonitoredResource{
 		Type:   k8sPod,

event-exporter/sinks/stackdriver/monitored_resource_factory_test.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 	sd "google.golang.org/api/logging/v2"
 	corev1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 )
 
 func TestMonitoredResourceFromEvent(t *testing.T) {
@@ -31,8 +32,11 @@ func TestMonitoredResourceFromEvent(t *testing.T) {
 			},
 		},
 		{
+			// Pod event whose involvedObject namespace matches the event's
+			// own metadata namespace is attributed to the pod.
 			config: newTypesConfig,
 			event: &corev1.Event{
+				ObjectMeta:     metav1.ObjectMeta{Namespace: "test_pod_namespace"},
 				InvolvedObject: corev1.ObjectReference{Kind: pod, Name: "test_pod_name", Namespace: "test_pod_namespace"},
 			},
 			wanted: &sd.MonitoredResource{
@@ -46,6 +50,40 @@ func TestMonitoredResourceFromEvent(t *testing.T) {
 				},
 			},
 		},
+		{
+			// Pod event whose involvedObject namespace disagrees with the
+			// event's own metadata namespace must not be attributed to the
+			// claimed pod; fall back to the cluster resource.
+			config: newTypesConfig,
+			event: &corev1.Event{
+				ObjectMeta:     metav1.ObjectMeta{Namespace: "user_namespace"},
+				InvolvedObject: corev1.ObjectReference{Kind: pod, Name: "test_pod_name", Namespace: "kube-system"},
+			},
+			wanted: &sd.MonitoredResource{
+				Type: k8sCluster,
+				Labels: map[string]string{
+					clusterName: newTypesConfig.clusterName,
+					location:    newTypesConfig.location,
+					projectID:   newTypesConfig.projectID,
+				},
+			},
+		},
+		{
+			// Pod event with no event-level namespace cannot be attributed
+			// to a pod; fall back to the cluster resource.
+			config: newTypesConfig,
+			event: &corev1.Event{
+				InvolvedObject: corev1.ObjectReference{Kind: pod, Name: "test_pod_name", Namespace: "kube-system"},
+			},
+			wanted: &sd.MonitoredResource{
+				Type: k8sCluster,
+				Labels: map[string]string{
+					clusterName: newTypesConfig.clusterName,
+					location:    newTypesConfig.location,
+					projectID:   newTypesConfig.projectID,
+				},
+			},
+		},
 		{
 			config: newTypesConfig,
 			event: &corev1.Event{