Add annotation to mount connect inject volume to other containers

CHANGELOG.md

@@ -7,6 +7,7 @@ BREAKING CHANGES:
 IMPROVEMENTS:
 * Control Plane
   * Upgrade Docker image Alpine version from 3.14 to 3.15. [[GH-1058](https://github.com/hashicorp/consul-k8s/pull/1058)]
+  * Support new annotation for mounting connect-inject volume to other containers. [[GH-1111](https://github.com/hashicorp/consul-k8s/pull/1111)]
 * Helm
   * API Gateway: Allow controller to read Kubernetes namespaces in order to determine if route is allowed for gateway. [[GH-1092](https://github.com/hashicorp/consul-k8s/pull/1092)]
 

control-plane/connect-inject/annotations.go

@@ -16,6 +16,12 @@ const (
 	// be set to a truthy or falsy value, as parseable by strconv.ParseBool.
 	annotationInject = "consul.hashicorp.com/connect-inject"
 
+	// annotationInjectMountVolumes is the key of the annotation that controls whether
+	// the data volume that connect inject uses to store data including the Consul ACL token
+	// is mounted to other containers in the pod. It is a comma-separated list of container names
+	// to mount the volume on. It will be mounted at the path `/consul/connect-inject`.
+	annotationInjectMountVolumes = "consul.hashicorp.com/connect-inject-mount-volume"
+
 	// annotationService is the name of the service to proxy.
 	// This defaults to the name of the Kubernetes service associated with the pod.
 	annotationService = "consul.hashicorp.com/connect-service"

control-plane/connect-inject/handler.go

@@ -209,6 +209,9 @@ func (h *Handler) Handle(ctx context.Context, req admission.Request) admission.R
 	// the sidecar for passing data in the pod.
 	pod.Spec.Volumes = append(pod.Spec.Volumes, h.containerVolume())
 
+	// Optionally mount data volume to other containers
+	h.injectVolumeMount(pod)
+
 	// Add the upstream services as environment variables for easy
 	// service discovery.
 	containerEnvVars := h.containerEnvVars(pod)
@@ -441,6 +444,19 @@ func (h *Handler) overwriteProbes(ns corev1.Namespace, pod *corev1.Pod) error {
 	return nil
 }
 
+func (h *Handler) injectVolumeMount(pod corev1.Pod) {
+	containersToInject := splitCommaSeparatedItemsFromAnnotation(annotationInjectMountVolumes, pod)
+
+	for index, container := range pod.Spec.Containers {
+		if sliceContains(containersToInject, container.Name) {
+			pod.Spec.Containers[index].VolumeMounts = append(pod.Spec.Containers[index].VolumeMounts, corev1.VolumeMount{
+				Name:      volumeName,
+				MountPath: "/consul/connect-inject",
+			})
+		}
+	}
+}
+
 func (h *Handler) shouldInject(pod corev1.Pod, namespace string) (bool, error) {
 	// Don't inject in the Kubernetes system namespaces
 	if kubeSystemNamespaces.Contains(namespace) {
@@ -625,3 +641,12 @@ func (h *Handler) InjectDecoder(d *admission.Decoder) error {
 	h.decoder = d
 	return nil
 }
+
+func sliceContains(slice []string, entry string) bool {
+	for _, s := range slice {
+		if entry == s {
+			return true
+		}
+	}
+	return false
+}

control-plane/connect-inject/handler_test.go

@@ -264,6 +264,127 @@ func TestHandlerHandle(t *testing.T) {
 			},
 		},
 
+		{
+			"pod with empty volume mount annotation",
+			Handler{
+				Log:                   logrtest.TestLogger{T: t},
+				AllowK8sNamespacesSet: mapset.NewSetWith("*"),
+				DenyK8sNamespacesSet:  mapset.NewSet(),
+				decoder:               decoder,
+				Clientset:             defaultTestClientWithNamespace(),
+			},
+			admission.Request{
+				AdmissionRequest: admissionv1.AdmissionRequest{
+					Namespace: namespaces.DefaultNamespace,
+					Object: encodeRaw(t, &corev1.Pod{
+						ObjectMeta: metav1.ObjectMeta{
+							Annotations: map[string]string{
+								annotationInjectMountVolumes: "",
+							},
+						},
+						Spec: basicSpec,
+					}),
+				},
+			},
+			"",
+			[]jsonpatch.Operation{
+				{
+					Operation: "add",
+					Path:      "/spec/volumes",
+				},
+				{
+					Operation: "add",
+					Path:      "/spec/initContainers",
+				},
+				{
+					Operation: "add",
+					Path:      "/spec/containers/1",
+				},
+				{
+					Operation: "add",
+					Path:      "/metadata/annotations/" + escapeJSONPointer(keyInjectStatus),
+				},
+				{
+					Operation: "add",
+					Path:      "/metadata/annotations/" + escapeJSONPointer(annotationOriginalPod),
+				},
+				{
+					Operation: "add",
+					Path:      "/metadata/labels",
+				},
+			},
+		},
+		{
+			"pod with volume mount annotation",
+			Handler{
+				Log:                   logrtest.TestLogger{T: t},
+				AllowK8sNamespacesSet: mapset.NewSetWith("*"),
+				DenyK8sNamespacesSet:  mapset.NewSet(),
+				decoder:               decoder,
+				Clientset:             defaultTestClientWithNamespace(),
+			},
+			admission.Request{
+				AdmissionRequest: admissionv1.AdmissionRequest{
+					Namespace: namespaces.DefaultNamespace,
+					Object: encodeRaw(t, &corev1.Pod{
+						ObjectMeta: metav1.ObjectMeta{
+							Annotations: map[string]string{
+								annotationInjectMountVolumes: "web,unknown,web_three_point_oh",
+							},
+						},
+						Spec: corev1.PodSpec{
+							Containers: []corev1.Container{
+								{
+									Name: "web",
+								},
+								{
+									Name: "web_two_point_oh",
+								},
+								{
+									Name: "web_three_point_oh",
+								},
+							},
+						},
+					}),
+				},
+			},
+			"",
+			[]jsonpatch.Operation{
+				{
+					Operation: "add",
+					Path:      "/spec/volumes",
+				},
+				{
+					Operation: "add",
+					Path:      "/spec/containers/0/volumeMounts",
+				},
+				{
+					Operation: "add",
+					Path:      "/spec/containers/2/volumeMounts",
+				},
+				{
+					Operation: "add",
+					Path:      "/spec/initContainers",
+				},
+				{
+					Operation: "add",
+					Path:      "/spec/containers/3",
+				},
+				{
+					Operation: "add",
+					Path:      "/metadata/annotations/" + escapeJSONPointer(keyInjectStatus),
+				},
+				{
+					Operation: "add",
+					Path:      "/metadata/annotations/" + escapeJSONPointer(annotationOriginalPod),
+				},
+				{
+					Operation: "add",
+					Path:      "/metadata/labels",
+				},
+			},
+		},
+
 		{
 			"pod with service annotation",
 			Handler{