Add pod metrics (#23844)

**Description:**
Add explicitly `k8s.node.allocatable_pods` to the list of Kubernetes
node metrics available, which went missing during the pdata translation

**Link to tracking Issue:**
#23839

Author: atoulme

.chloggen/add-back-pods-metrics.yaml

@@ -0,0 +1,20 @@
+# Use this changelog template to create an entry for release notes.
+# If your change doesn't affect end users, such as a test fix or a tooling change,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: bug_fix
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: k8sclusterreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add explicitly `k8s.node.allocatable_pods` to the list of Kubernetes node metrics available, which went missing during the pdata translation
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [23839]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:

receiver/k8sclusterreceiver/internal/node/documentation.md

@@ -38,6 +38,14 @@ How many bytes of RAM memory remaining that the node can allocate to pods
 | ---- | ----------- | ---------- |
 | By | Gauge | Int |
 
+### k8s.node.allocatable_pods
+
+How many pods remaining the node can allocate
+
+| Unit | Metric Type | Value Type |
+| ---- | ----------- | ---------- |
+| {pods} | Gauge | Int |
+
 ### k8s.node.allocatable_storage
 
 How many bytes of storage remaining that the node can allocate to pods

receiver/k8sclusterreceiver/internal/node/internal/metadata/generated_config.go

@@ -7,6 +7,8 @@ all_set:
       enabled: true
     k8s.node.allocatable_memory:
       enabled: true
+    k8s.node.allocatable_pods:
+      enabled: true
     k8s.node.allocatable_storage:
       enabled: true
     k8s.node.condition_disk_pressure:
@@ -34,6 +36,8 @@ none_set:
       enabled: false
     k8s.node.allocatable_memory:
       enabled: false
+    k8s.node.allocatable_pods:
+      enabled: false
     k8s.node.allocatable_storage:
       enabled: false
     k8s.node.condition_disk_pressure:

receiver/k8sclusterreceiver/internal/node/internal/metadata/generated_config_test.go

@@ -73,5 +73,11 @@ metrics:
     enabled: true
     description: How many bytes of storage remaining that the node can allocate to pods
     unit: "By"
+    gauge:
+      value_type: int
+  k8s.node.allocatable_pods:
+    enabled: true
+    description: How many pods remaining the node can allocate
+    unit: "{pods}"
     gauge:
       value_type: int

receiver/k8sclusterreceiver/internal/node/internal/metadata/generated_metrics.go

@@ -86,6 +86,8 @@ func GetMetrics(set receiver.CreateSettings, node *corev1.Node, nodeConditionTyp
 			mb.RecordK8sNodeAllocatableEphemeralStorageDataPoint(ts, quantity.Value())
 		case corev1.ResourceStorage:
 			mb.RecordK8sNodeAllocatableStorageDataPoint(ts, quantity.Value())
+		case corev1.ResourcePods:
+			mb.RecordK8sNodeAllocatablePodsDataPoint(ts, quantity.Value())
 		default:
 			set.Logger.Warn("unknown node condition type", zap.Any("conditionType", v1NodeAllocatableTypeValue))
 		}

receiver/k8sclusterreceiver/internal/node/internal/metadata/generated_metrics_test.go

@@ -31,6 +31,12 @@ resourceMetrics:
                 - asInt: "456"
             name: k8s.node.allocatable_memory
             unit: By
+          - description: How many pods remaining the node can allocate
+            gauge:
+              dataPoints:
+                - asInt: "12"
+            name: k8s.node.allocatable_pods
+            unit: "{pods}"
           - description: Whether this node is DiskPressure (1), not DiskPressure (0) or in an unknown state (-1)
             gauge:
               dataPoints: