[7.x](backport #27707) Add support for ephemeral containers in elastic agent dynamic provider

x-pack/elastic-agent/CHANGELOG.next.asciidoc

@@ -135,3 +135,4 @@
 - Add new --enroll-delay option for install and enroll commands. {pull}27118[27118]
 - Add link to troubleshooting guide on fatal exits. {issue}26367[26367] {pull}27236[27236]
 - Agent now adapts the beats queue size based on output settings. {issue}26638[26638] {pull}27429[27429]
+- Support ephemeral containers in Kubernetes dynamic provider. {issue}#27020[#27020] {pull}27707[27707]

x-pack/elastic-agent/pkg/composable/providers/kubernetes/pod.go

@@ -67,7 +67,11 @@ func (p *pod) emitRunning(pod *kubernetes.Pod) {
 
 	// TODO: deal with init containers stopping after initialization
 	p.emitContainers(pod, pod.Spec.InitContainers, pod.Status.InitContainerStatuses)
-	// TODO: deal with ephemeral containers
+
+	// Get ephemeral containers and their status
+	ephContainers, ephContainersStatuses := getEphemeralContainers(pod)
+	p.emitContainers(pod, ephContainers, ephContainersStatuses)
+
 }
 
 func (p *pod) emitContainers(pod *kubernetes.Pod, containers []kubernetes.Container, containerstatuses []kubernetes.PodContainerStatus) {
@@ -222,3 +226,16 @@ func generateContainerData(
 		comm.AddOrUpdate(eventID, ContainerPriority, mapping, processors)
 	}
 }
+
+func getEphemeralContainers(pod *kubernetes.Pod) ([]kubernetes.Container, []kubernetes.PodContainerStatus) {
+	var ephContainers []kubernetes.Container
+	var ephContainersStatuses []kubernetes.PodContainerStatus
+	for _, c := range pod.Spec.EphemeralContainers {
+		c := kubernetes.Container(c.EphemeralContainerCommon)
+		ephContainers = append(ephContainers, c)
+	}
+	for _, s := range pod.Status.EphemeralContainerStatuses {
+		ephContainersStatuses = append(ephContainersStatuses, s)
+	}
+	return ephContainers, ephContainersStatuses
+}

x-pack/elastic-agent/pkg/composable/providers/kubernetes/pod_test.go

@@ -166,6 +166,79 @@ func TestGenerateContainerPodData(t *testing.T) {
 
 }
 
+func TestGetEphemeralContainers(t *testing.T) {
+	name := "filebeat"
+	namespace := "default"
+	podIP := "127.0.0.1"
+	containerID := "docker://foobar"
+	uid := "005f3b90-4b9d-12f8-acf0-31020a840133"
+	containerImage := "elastic/filebeat:6.3.0"
+	node := "node"
+
+	expectedEphemeralContainers :=
+		[]kubernetes.Container{
+			{
+				Name:  "filebeat",
+				Image: "elastic/filebeat:6.3.0",
+			},
+		}
+	expectedephemeralContainersStatuses :=
+		[]kubernetes.PodContainerStatus{
+			{
+				Name: "filebeat",
+				State: v1.ContainerState{
+					Running: &v1.ContainerStateRunning{
+						StartedAt: metav1.Time{},
+					},
+				},
+				Ready:       false,
+				ContainerID: "docker://foobar",
+			},
+		}
+
+	pod :=
+		&kubernetes.Pod{
+			ObjectMeta: metav1.ObjectMeta{
+				Name:        name,
+				UID:         types.UID(uid),
+				Namespace:   namespace,
+				Labels:      map[string]string{},
+				Annotations: map[string]string{},
+			},
+			TypeMeta: metav1.TypeMeta{
+				Kind:       "Pod",
+				APIVersion: "v1",
+			},
+			Status: v1.PodStatus{
+				PodIP: podIP,
+				Phase: kubernetes.PodRunning,
+				EphemeralContainerStatuses: []kubernetes.PodContainerStatus{
+					{
+						Name:        name,
+						ContainerID: containerID,
+						State: v1.ContainerState{
+							Running: &v1.ContainerStateRunning{},
+						},
+					},
+				},
+			},
+			Spec: v1.PodSpec{
+				NodeName: node,
+				EphemeralContainers: []v1.EphemeralContainer{
+					{
+						EphemeralContainerCommon: v1.EphemeralContainerCommon{
+							Image: containerImage,
+							Name:  name,
+						},
+					},
+				},
+			},
+		}
+	ephContainers, ephContainersStatuses := getEphemeralContainers(pod)
+	assert.Equal(t, expectedEphemeralContainers, ephContainers)
+	assert.Equal(t, expectedephemeralContainersStatuses, ephContainersStatuses)
+}
+
 // MockDynamicComm is used in tests.
 type MockDynamicComm struct {
 	context.Context