prometheus: Add ability to whitelist Kubernetes labels

Documentation/api.md

@@ -318,6 +318,7 @@ ServiceMonitorSpec contains specification parameters for a ServiceMonitor.
 | Field | Description | Scheme | Required |
 | ----- | ----------- | ------ | -------- |
 | jobLabel | The label to use to retrieve the job name from. | string | false |
+| targetLabels | TargetLabels transfers labels on the Kubernetes Service onto the target. | []string | false |
 | endpoints | A list of endpoints allowed as part of this ServiceMonitor. | [][Endpoint](#endpoint) | true |
 | selector | Selector to select Endpoints objects. | [metav1.LabelSelector](https://v1-6.docs.kubernetes.io/docs/api-reference/v1.6/#labelselector-v1-meta) | true |
 | namespaceSelector | Selector to select which namespaces the Endpoints objects are discovered from. | [NamespaceSelector](#namespaceselector) | false |

contrib/kube-prometheus/manifests/examples/example-app/example-app.yaml

@@ -1,13 +1,13 @@
 kind: Service
 apiVersion: v1
-metadata: 
+metadata:
   name: example-app
   labels:
     tier: frontend
   namespace: default
-spec: 
-  selector: 
-    app: example-app 
+spec:
+  selector:
+    app: example-app
   ports:
   - name: web
     protocol: TCP

contrib/kube-prometheus/manifests/examples/example-app/servicemonitor-frontend.yaml

@@ -9,6 +9,8 @@ spec:
   selector:
     matchLabels:
       tier: frontend
+  targetLabels:
+    - tier
   endpoints:
   - port: web
     interval: 10s

example/prometheus-operator-crd/servicemonitor.crd.yaml

@@ -221,6 +221,12 @@ spec:
                     "In", and the values array contains only "value". The requirements
                     are ANDed.
                   type: object
+            targetLabels:
+              description: TargetLabels transfers labels on the Kubernetes Service
+                onto the target.
+              items:
+                type: string
+              type: array
           required:
           - endpoints
           - selector

pkg/client/monitoring/v1/openapi_generated.go

@@ -1242,6 +1242,20 @@ func GetOpenAPIDefinitions(ref common.ReferenceCallback) map[string]common.OpenA
 								Format:      "",
 							},
 						},
+						"targetLabels": {
+							SchemaProps: spec.SchemaProps{
+								Description: "TargetLabels transfers labels on the Kubernetes Service onto the target.",
+								Type:        []string{"array"},
+								Items: &spec.SchemaOrArray{
+									Schema: &spec.Schema{
+										SchemaProps: spec.SchemaProps{
+											Type:   []string{"string"},
+											Format: "",
+										},
+									},
+								},
+							},
+						},
 						"endpoints": {
 							SchemaProps: spec.SchemaProps{
 								Description: "A list of endpoints allowed as part of this ServiceMonitor.",

pkg/client/monitoring/v1/types.go

@@ -294,6 +294,8 @@ type ServiceMonitor struct {
 type ServiceMonitorSpec struct {
 	// The label to use to retrieve the job name from.
 	JobLabel string `json:"jobLabel,omitempty"`
+	// TargetLabels transfers labels on the Kubernetes Service onto the target.
+	TargetLabels []string `json:"targetLabels,omitempty"`
 	// A list of endpoints allowed as part of this ServiceMonitor.
 	Endpoints []Endpoint `json:"endpoints"`
 	// Selector to select Endpoints objects.

pkg/client/monitoring/v1/zz_generated.deepcopy.go

@@ -732,6 +732,11 @@ func (in *ServiceMonitorList) DeepCopy() *ServiceMonitorList {
 // DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
 func (in *ServiceMonitorSpec) DeepCopyInto(out *ServiceMonitorSpec) {
 	*out = *in
+	if in.TargetLabels != nil {
+		in, out := &in.TargetLabels, &out.TargetLabels
+		*out = make([]string, len(*in))
+		copy(*out, *in)
+	}
 	if in.Endpoints != nil {
 		in, out := &in.Endpoints, &out.Endpoints
 		*out = make([]Endpoint, len(*in))

pkg/prometheus/promcfg.go

@@ -345,6 +345,16 @@ func generateServiceMonitorConfig(version semver.Version, m *v1.ServiceMonitor,
 		},
 	}...)
 
+	// Relabel targetLabels from Service onto target.
+	for _, l := range m.Spec.TargetLabels {
+		relabelings = append(relabelings, yaml.MapSlice{
+			{Key: "source_labels", Value: []string{"__meta_kubernetes_service_label_" + sanitizeLabelName(l)}},
+			{Key: "target_label", Value: sanitizeLabelName(l)},
+			{Key: "regex", Value: "(.+)"},
+			{Key: "replacement", Value: "${1}"},
+		})
+	}
+
 	// By default, generate a safe job name from the service name.  We also keep
 	// this around if a jobLabel is set in case the targets don't actually have a
 	// value for it. A single service may potentially have multiple metrics