Replace special string "<none>" with empty string for "storageclass" dimension.

Returning empty string instead of special string "<none>" for "storageclass" dimensions of "kube_persistentvolumeclaim_info" metric.

Author: pawcykca

docs/persistentvolumeclaim-metrics.md

@@ -13,4 +13,4 @@
 
 Note:
 
-- A special `<none>` string will be used if PVC has no storage class.
+- An empty string will be used if PVC has no storage class.

internal/store/persistentvolumeclaim.go

@@ -270,6 +270,6 @@ func getPersistentVolumeClaimClass(claim *v1.PersistentVolumeClaim) string {
 		return *claim.Spec.StorageClassName
 	}
 
-	// Special non-empty string to indicate absence of storage class.
-	return "<none>"
+	// An empty string indicate absence of storage class.
+	return ""
 }

internal/store/persistentvolumeclaim_test.go

@@ -257,7 +257,7 @@ func TestPersistentVolumeClaimStore(t *testing.T) {
 				# TYPE kube_persistentvolumeclaim_status_phase gauge
 				# TYPE kube_persistentvolumeclaim_status_condition gauge
 				kube_persistentvolumeclaim_created{namespace="",persistentvolumeclaim="mongo-data"} 1.5e+09
-				kube_persistentvolumeclaim_info{namespace="",persistentvolumeclaim="mongo-data",storageclass="<none>",volumename=""} 1
+				kube_persistentvolumeclaim_info{namespace="",persistentvolumeclaim="mongo-data",storageclass="",volumename=""} 1
 				kube_persistentvolumeclaim_status_phase{namespace="",persistentvolumeclaim="mongo-data",phase="Bound"} 0
 				kube_persistentvolumeclaim_status_phase{namespace="",persistentvolumeclaim="mongo-data",phase="Lost"} 1
 				kube_persistentvolumeclaim_status_phase{namespace="",persistentvolumeclaim="mongo-data",phase="Pending"} 0