Merge pull request #1936 from CatherineF-dev/update-develop-doc-2

Add develop doc on adding new metrics

Author: k8s-ci-robot

docs/developer/guide.md

@@ -6,6 +6,7 @@ Any contribution to improving this documentation will be appreciated.
 ## Table of Contents
 
 - [Add New Kubernetes Resource Metric Collector](#add-new-kubernetes-resource-metric-collector)
+- [Add New Metrics](#add-new-metrics)
 
 ### Add New Kubernetes Resource Metric Collector
 
@@ -20,3 +21,13 @@ The following steps are needed to introduce a new resource and its respective re
 - Reference the new resource in [pkg/options/resource.go](https://github.com/kubernetes/kube-state-metrics/blob/main/pkg/options/resource.go).
 - Add a sample Kubernetes manifest to be used by tests in the [tests/manifests/](https://github.com/kubernetes/kube-state-metrics/tree/main/tests/manifests) directory.
 - Lastly, and most importantly, actually implement your new resource(s) and its test binary in [internal/store](https://github.com/kubernetes/kube-state-metrics/tree/main/internal/store). Follow the formatting and structure of other resources.
+
+### Add New Metrics
+
+- Make metrics experimental first when introducing them, refer [#1910](https://github.com/kubernetes/kube-state-metrics/pull/1910) for more information.
+
+| Metric stability level |                    |
+|------------------------|--------------------|
+| EXPERIMENTAL           | basemetrics.ALPHA  |
+| STABLE                 | basemetrics.STABLE |
+

docs/statefulset-metrics.md

@@ -11,7 +11,7 @@
 | kube_statefulset_status_observed_generation | Gauge | `statefulset`=&lt;statefulset-name&gt; <br> `namespace`=&lt;statefulset-namespace&gt;  | STABLE |
 | kube_statefulset_replicas | Gauge | `statefulset`=&lt;statefulset-name&gt; <br> `namespace`=&lt;statefulset-namespace&gt;  | STABLE |
 | kube_statefulset_metadata_generation | Gauge | `statefulset`=&lt;statefulset-name&gt; <br> `namespace`=&lt;statefulset-namespace&gt;  | STABLE |
-| kube_statefulset_persistentvolumeclaim_retention_policy | Gauge | `statefulset`=&lt;statefulset-name&gt; <br> `namespace`=&lt;statefulset-namespace&gt; <br> `when_deleted`=&lt;statefulset-when-deleted-pvc-policy&gt; <br> `when_scaled`=&lt;statefulset-when-scaled-pvc-policy&gt; | ALPHA |
+| kube_statefulset_persistentvolumeclaim_retention_policy | Gauge | `statefulset`=&lt;statefulset-name&gt; <br> `namespace`=&lt;statefulset-namespace&gt; <br> `when_deleted`=&lt;statefulset-when-deleted-pvc-policy&gt; <br> `when_scaled`=&lt;statefulset-when-scaled-pvc-policy&gt; | EXPERIMENTAL |
 | kube_statefulset_created | Gauge | `statefulset`=&lt;statefulset-name&gt; <br> `namespace`=&lt;statefulset-namespace&gt;  | STABLE |
 | kube_statefulset_labels | Gauge | `statefulset`=&lt;statefulset-name&gt; <br> `namespace`=&lt;statefulset-namespace&gt; <br> `label_STATEFULSET_LABEL`=&lt;STATEFULSET_LABEL&gt; | STABLE |
 | kube_statefulset_status_current_revision | Gauge | `statefulset`=&lt;statefulset-name&gt; <br> `namespace`=&lt;statefulset-namespace&gt; <br> `revision`=&lt;statefulset-current-revision&gt; | STABLE |