Expose controller kind and name to labelling rules

Relabelling rules can use this information to attach the name of the controller
that has created a pod.

In turn, this can be used to slice metrics by workload at query time, ie.
"Give me all metrics that have been created by the $name Deployment"

Signed-off-by: Damien Lespiau <damien@weave.works>

discovery/kubernetes/pod.go

@@ -23,6 +23,7 @@ import (
 	"github.com/go-kit/kit/log"
 	"github.com/go-kit/kit/log/level"
 	"github.com/prometheus/common/model"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/client-go/pkg/api"
 	apiv1 "k8s.io/client-go/pkg/api/v1"
 	"k8s.io/client-go/tools/cache"
@@ -147,8 +148,21 @@ const (
 	podNodeNameLabel              = metaLabelPrefix + "pod_node_name"
 	podHostIPLabel                = metaLabelPrefix + "pod_host_ip"
 	podUID                        = metaLabelPrefix + "pod_uid"
+	podControllerKind             = metaLabelPrefix + "pod_controller_kind"
+	podControllerName             = metaLabelPrefix + "pod_controller_name"
 )
 
+// GetControllerOf returns a pointer to a copy of the controllerRef if controllee has a controller
+// https://github.com/kubernetes/apimachinery/blob/cd2cae2b39fa57e8063fa1f5f13cfe9862db3d41/pkg/apis/meta/v1/controller_ref.go
+func GetControllerOf(controllee metav1.Object) *metav1.OwnerReference {
+	for _, ref := range controllee.GetOwnerReferences() {
+		if ref.Controller != nil && *ref.Controller {
+			return &ref
+		}
+	}
+	return nil
+}
+
 func podLabels(pod *apiv1.Pod) model.LabelSet {
 	ls := model.LabelSet{
 		podNameLabel:     lv(pod.ObjectMeta.Name),
@@ -159,6 +173,16 @@ func podLabels(pod *apiv1.Pod) model.LabelSet {
 		podUID:           lv(string(pod.ObjectMeta.UID)),
 	}
 
+	createdBy := GetControllerOf(pod)
+	if createdBy != nil {
+		if createdBy.Kind != "" {
+			ls[podControllerKind] = lv(createdBy.Kind)
+		}
+		if createdBy.Name != "" {
+			ls[podControllerName] = lv(createdBy.Name)
+		}
+	}
+
 	for k, v := range pod.Labels {
 		ln := strutil.SanitizeLabelName(podLabelPrefix + k)
 		ls[model.LabelName(ln)] = lv(v)

discovery/kubernetes/pod_test.go

@@ -23,6 +23,10 @@ import (
 	"k8s.io/client-go/pkg/api/v1"
 )
 
+func makeOptionalBool(v bool) *bool {
+	return &v
+}
+
 func makeMultiPortPods() *v1.Pod {
 	return &v1.Pod{
 		ObjectMeta: metav1.ObjectMeta{
@@ -31,6 +35,13 @@ func makeMultiPortPods() *v1.Pod {
 			Labels:      map[string]string{"testlabel": "testvalue"},
 			Annotations: map[string]string{"testannotation": "testannotationvalue"},
 			UID:         types.UID("abc123"),
+			OwnerReferences: []metav1.OwnerReference{
+				{
+					Kind:       "testcontrollerkind",
+					Name:       "testcontrollername",
+					Controller: makeOptionalBool(true),
+				},
+			},
 		},
 		Spec: v1.PodSpec{
 			NodeName: "testnode",
@@ -146,6 +157,8 @@ func TestPodDiscoveryBeforeRun(t *testing.T) {
 					"__meta_kubernetes_pod_host_ip":                   "2.3.4.5",
 					"__meta_kubernetes_pod_ready":                     "true",
 					"__meta_kubernetes_pod_uid":                       "abc123",
+					"__meta_kubernetes_pod_controller_kind":           "testcontrollerkind",
+					"__meta_kubernetes_pod_controller_name":           "testcontrollername",
 				},
 				Source: "pod/default/testpod",
 			},

docs/configuration/configuration.md

@@ -694,6 +694,8 @@ Available meta labels:
 * `__meta_kubernetes_pod_node_name`: The name of the node the pod is scheduled onto.
 * `__meta_kubernetes_pod_host_ip`: The current host IP of the pod object.
 * `__meta_kubernetes_pod_uid`: The UID of the pod object.
+* `__meta_kubernetes_pod_controller_kind`: Object kind of the pod controller.
+* `__meta_kubernetes_pod_controller_name`: Name of the pod controller.
 
 #### `endpoints`