Add KSM CR metrics (#32716)

* Add KSM CR metrics

* Fixes after review

* Update configuration.md

---------

Co-authored-by: cecilia saixue wat-kim <cecilia.watt@datadoghq.com>

Author: bitomaxsp

content/en/infrastructure/containers/configuration.md

@@ -411,7 +411,110 @@ field#status.conditions.HorizontalAbleToScale.status:"False"
 
 <div class="alert alert-info">You can select up to 50 fields per resource. You can use the preview to validate your indexing choices.</div>
 
+### Collect custom resource metrics using Kubernetes State Core check
+
+<div class="alert alert-info">This functionality requires Cluster Agent 7.63.0+.</div>
+
+You can use the `kubernetes_state_core` check to collect custom resource metrics when running the Datadog Cluster Agent.
+
+1. Write defintions for your custom resources and the fields to turn into metrics according to the following format:
+
+   ```yaml
+   #=(...)
+   collectCrMetrics:
+     - groupVersionKind:
+         group: "crd.k8s.amazonaws.com"
+         kind: "ENIConfig"
+         version: "v1alpha1"
+       commonLabels:
+         crd_type: "eniconfig"
+       labelsFromPath:
+         crd_name: [metadata, name]
+       metrics:
+         - name: "eniconfig"
+           help: "ENI Config"
+           each:
+             type: gauge
+             gauge:
+               path: [metadata, generation]
+     - groupVersionKind:
+         group: "vpcresources.k8s.aws"
+         kind: "CNINode"
+         version: "v1alpha1"
+         resource: "cninode-pluralized"
+       commonLabels:
+         crd_type: "cninode"
+       labelsFromPath:
+         crd_name: [metadata, name]
+       metrics:
+         - name: "cninode"
+           help: "CNI Node"
+           each:
+             type: gauge
+             gauge:
+               path: [metadata, generation]
+   ```
+
+   For more details, see [Custom Resource State Metrics][5].
+   
+2. Update your Helm or Datadog Operator configuration:
 
+   {{< tabs >}}
+   {{% tab "Helm Chart" %}}
+
+   1. Add the following configuration to `datadog-values.yaml`:
+
+      ```yaml
+      datadog:
+        #(...)
+        kubeStateMetricsCore:
+          collectCrMetrics:
+            - <CUSTOM_RESOURCE_METRIC>
+      ```
+
+       Replace `<CUSTOM_RESOURCE_METRIC>` with the definitions you wrote in the first step.
+
+   1. Upgrade your Helm chart:
+
+      ```
+      helm upgrade -f datadog-values.yaml <RELEASE_NAME> datadog/datadog
+      ```
+
+   {{% /tab %}}
+   {{% tab "Datadog Operator" %}}
+
+   1. Install the Datadog Operator with an option that grants the Datadog Agent permission to collect custom resources:
+
+      ```
+      helm install datadog-operator datadog/datadog-operator --set clusterRole.allowReadAllResources=true
+      ```
+
+   1. Add the following configuration to your `DatadogAgent` manifest, `datadog-agent.yaml`:
+
+      ```yaml
+      apiVersion: datadoghq.com/v2alpha1
+      kind: DatadogAgent
+      metadata:
+        name: datadog
+      spec:
+        #(...)
+        features:
+          kubeStateMetricsCore:
+            collectCrMetrics:
+              - <CUSTOM_RESOURCE_METRIC>
+      ```
+
+      Replace `<CUSTOM_RESOURCE_METRIC>` with the definitions you wrote in the first step.
+
+   1. Apply your new configuration:
+
+      ```
+      kubectl apply -n $DD_NAMESPACE -f datadog-agent.yaml
+      ```
+
+   {{% /tab %}}
+   {{< /tabs >}}
+   
 ## Further reading
 
 {{< partial name="whats-next/whats-next.html" >}}
@@ -420,4 +523,4 @@ field#status.conditions.HorizontalAbleToScale.status:"False"
 [2]: /infrastructure/containers
 [3]: https://app.datadoghq.com/orchestration/explorer/pod
 [4]: https://app.datadoghq.com/orchestration/explorer/crd
-
+[5]: https://github.com/kubernetes/kube-state-metrics/blob/main/docs/metrics/extend/customresourcestate-metrics.md