Add PVC metrics for VolumeAttributesClass (VAC) support

Expose the desired vs. currently-applied VolumeAttributesClass on a
PersistentVolumeClaim, and the state of any in-progress ModifyVolume
operation, via three new EXPERIMENTAL metrics:
kube_persistentvolumeclaim_volume_attributes_class,
kube_persistentvolumeclaim_status_current_volume_attributes_class, and
kube_persistentvolumeclaim_status_modify_volume_status.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Author: FRosner

docs/metrics/storage/persistentvolumeclaim-metrics.md

@@ -11,6 +11,9 @@
 | kube_persistentvolumeclaim_status_phase                    | Gauge       |                                                                                                                           |                         | `namespace`=&lt;persistentvolumeclaim-namespace&gt; <br> `persistentvolumeclaim`=&lt;persistentvolumeclaim-name&gt; <br> `phase`=&lt;Pending\Bound\Lost&gt;                                                                                                  | STABLE       |
 | kube_persistentvolumeclaim_created                         | Gauge       | Unix creation timestamp                                                                                                   | seconds                 | `namespace`=&lt;persistentvolumeclaim-namespace&gt; <br> `persistentvolumeclaim`=&lt;persistentvolumeclaim-name&gt;                                                                                                                                          | EXPERIMENTAL |
 | kube_persistentvolumeclaim_deletion_timestamp              | Gauge       | Unix deletion timestamp                                                                                                   | seconds                 | `namespace`=&lt;persistentvolumeclaim-namespace&gt; <br> `persistentvolumeclaim`=&lt;persistentvolumeclaim-name&gt;                                                                                                                                          | EXPERIMENTAL |
+| kube_persistentvolumeclaim_volume_attributes_class          | Gauge       | The name of the VolumeAttributesClass requested by the persistent volume claim.                                         |                         | `namespace`=&lt;persistentvolumeclaim-namespace&gt; <br> `persistentvolumeclaim`=&lt;persistentvolumeclaim-name&gt; <br> `volume_attributes_class`=&lt;volume-attributes-class-name&gt;                                                                      | EXPERIMENTAL |
+| kube_persistentvolumeclaim_status_current_volume_attributes_class | Gauge | The current VolumeAttributesClass applied to the persistent volume claim, as reported by the CSI driver.               |                         | `namespace`=&lt;persistentvolumeclaim-namespace&gt; <br> `persistentvolumeclaim`=&lt;persistentvolumeclaim-name&gt; <br> `volume_attributes_class`=&lt;volume-attributes-class-name&gt;                                                                      | EXPERIMENTAL |
+| kube_persistentvolumeclaim_status_modify_volume_status      | Gauge       | Information about the status of an in-progress ModifyVolume operation on the persistent volume claim.                  |                         | `namespace`=&lt;persistentvolumeclaim-namespace&gt; <br> `persistentvolumeclaim`=&lt;persistentvolumeclaim-name&gt; <br> `status`=&lt;Pending\InProgress\Infeasible&gt; <br> `target_volume_attributes_class`=&lt;volume-attributes-class-name&gt;          | EXPERIMENTAL |
 
 Note:
 

internal/store/persistentvolumeclaim.go

@@ -112,6 +112,94 @@ func persistentVolumeClaimMetricFamilies(allowAnnotationsList, allowLabelsList [
 				}
 			}),
 		),
+		*generator.NewFamilyGeneratorWithStability(
+			"kube_persistentvolumeclaim_volume_attributes_class",
+			"The name of the VolumeAttributesClass requested by the persistent volume claim.",
+			metric.Gauge,
+			basemetrics.ALPHA,
+			"",
+			wrapPersistentVolumeClaimFunc(func(p *v1.PersistentVolumeClaim) *metric.Family {
+				volumeAttributesClassName := ""
+				if p.Spec.VolumeAttributesClassName != nil {
+					volumeAttributesClassName = *p.Spec.VolumeAttributesClassName
+				}
+
+				return &metric.Family{
+					Metrics: []*metric.Metric{
+						{
+							LabelKeys:   []string{"volume_attributes_class"},
+							LabelValues: []string{volumeAttributesClassName},
+							Value:       1,
+						},
+					},
+				}
+			}),
+		),
+		*generator.NewFamilyGeneratorWithStability(
+			"kube_persistentvolumeclaim_status_current_volume_attributes_class",
+			"The current VolumeAttributesClass applied to the persistent volume claim, as reported by the CSI driver.",
+			metric.Gauge,
+			basemetrics.ALPHA,
+			"",
+			wrapPersistentVolumeClaimFunc(func(p *v1.PersistentVolumeClaim) *metric.Family {
+				currentVolumeAttributesClassName := ""
+				if p.Status.CurrentVolumeAttributesClassName != nil {
+					currentVolumeAttributesClassName = *p.Status.CurrentVolumeAttributesClassName
+				}
+
+				return &metric.Family{
+					Metrics: []*metric.Metric{
+						{
+							LabelKeys:   []string{"volume_attributes_class"},
+							LabelValues: []string{currentVolumeAttributesClassName},
+							Value:       1,
+						},
+					},
+				}
+			}),
+		),
+		*generator.NewFamilyGeneratorWithStability(
+			"kube_persistentvolumeclaim_status_modify_volume_status",
+			"Information about the status of an in-progress ModifyVolume operation on the persistent volume claim.",
+			metric.Gauge,
+			basemetrics.ALPHA,
+			"",
+			wrapPersistentVolumeClaimFunc(func(p *v1.PersistentVolumeClaim) *metric.Family {
+				modifyVolumeStatus := p.Status.ModifyVolumeStatus
+
+				if modifyVolumeStatus == nil {
+					return &metric.Family{
+						Metrics: []*metric.Metric{},
+					}
+				}
+
+				status := modifyVolumeStatus.Status
+				targetVolumeAttributesClass := modifyVolumeStatus.TargetVolumeAttributesClassName
+
+				ms := []*metric.Metric{
+					{
+						LabelValues: []string{string(v1.PersistentVolumeClaimModifyVolumePending), targetVolumeAttributesClass},
+						Value:       boolFloat64(status == v1.PersistentVolumeClaimModifyVolumePending),
+					},
+					{
+						LabelValues: []string{string(v1.PersistentVolumeClaimModifyVolumeInProgress), targetVolumeAttributesClass},
+						Value:       boolFloat64(status == v1.PersistentVolumeClaimModifyVolumeInProgress),
+					},
+					{
+						LabelValues: []string{string(v1.PersistentVolumeClaimModifyVolumeInfeasible), targetVolumeAttributesClass},
+						Value:       boolFloat64(status == v1.PersistentVolumeClaimModifyVolumeInfeasible),
+					},
+				}
+
+				for _, m := range ms {
+					m.LabelKeys = []string{"status", "target_volume_attributes_class"}
+				}
+
+				return &metric.Family{
+					Metrics: ms,
+				}
+			}),
+		),
 		*generator.NewFamilyGeneratorWithStability(
 			"kube_persistentvolumeclaim_status_phase",
 			"The phase the persistent volume claim is currently in.",