[receiver/k8scluster] add hpa.scaletargetref attrs (open-telemetry#40063)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description

Adds new resource attributes to `k8s.hpa`. These attributes track the
target resource a given HPA is configured to scale. The attributes are -
`k8s.hpa.scaletargetref.kind`, `k8s.hpa.scaletargetref.name`, and
`k8s.hpa.scaletargetref.apiversion`. These attributes are disabled by
default.

PR for semantic-conventions is available
[here](open-telemetry/semantic-conventions#2180).

<!-- Issue number (e.g. open-telemetry#1234) or full URL to issue, if applicable. -->
#### Link to tracking issue
Fixes open-telemetry#38768

<!--Describe what testing was performed and which tests were added.-->
#### Testing
Added unit tests
Tested manually in a k8s cluster

<!--Describe the documentation added.-->
#### Documentation
Documentation updated with new attribute names

<!--Please delete paragraphs that you did not use before submitting.-->

Author: jinja2

.chloggen/hpa-scaletarget-attrs.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: receiver/k8sclusterreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Added new resource attributes `k8s.hpa.scaletargetref.kind`, `k8s.hpa.scaletargetref.name`, and `k8s.hpa.scaletargetref.apiversion` to the `k8s.hpa` resource.  These attributes are disabled by default.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [38768]
+
+# (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:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

receiver/k8sclusterreceiver/documentation.md

@@ -436,6 +436,9 @@ Current status reason of the pod (1 - Evicted, 2 - NodeAffinity, 3 - NodeLost, 4
 | k8s.deployment.name | The name of the Deployment. | Any Str | true |
 | k8s.deployment.uid | The UID of the Deployment. | Any Str | true |
 | k8s.hpa.name | The k8s hpa name. | Any Str | true |
+| k8s.hpa.scaletargetref.apiversion | The API version of the target resource to scale for the HorizontalPodAutoscaler. | Any Str | false |
+| k8s.hpa.scaletargetref.kind | The kind of the target resource to scale for the HorizontalPodAutoscaler. | Any Str | false |
+| k8s.hpa.scaletargetref.name | The name of the target resource to scale for the HorizontalPodAutoscaler. | Any Str | false |
 | k8s.hpa.uid | The k8s hpa uid. | Any Str | true |
 | k8s.job.name | The k8s pod name. | Any Str | true |
 | k8s.job.uid | The k8s job uid. | Any Str | true |

receiver/k8sclusterreceiver/internal/hpa/hpa.go

@@ -20,6 +20,9 @@ func RecordMetrics(mb *metadata.MetricsBuilder, hpa *autoscalingv2.HorizontalPod
 	rb.SetK8sHpaUID(string(hpa.UID))
 	rb.SetK8sHpaName(hpa.Name)
 	rb.SetK8sNamespaceName(hpa.Namespace)
+	rb.SetK8sHpaScaletargetrefApiversion(hpa.Spec.ScaleTargetRef.APIVersion)
+	rb.SetK8sHpaScaletargetrefKind(hpa.Spec.ScaleTargetRef.Kind)
+	rb.SetK8sHpaScaletargetrefName(hpa.Spec.ScaleTargetRef.Name)
 	mb.EmitForResource(metadata.WithResource(rb.Emit()))
 }
 

receiver/k8sclusterreceiver/internal/hpa/hpa_test.go

@@ -46,3 +46,32 @@ func TestHPAMetrics(t *testing.T) {
 	testutils.AssertMetricInt(t, sms.Metrics().At(2), "k8s.hpa.max_replicas", pmetric.MetricTypeGauge, 10)
 	testutils.AssertMetricInt(t, sms.Metrics().At(3), "k8s.hpa.min_replicas", pmetric.MetricTypeGauge, 2)
 }
+
+func TestHPAResAttrs(t *testing.T) {
+	hpa := testutils.NewHPA("1")
+
+	ts := pcommon.Timestamp(time.Now().UnixNano())
+
+	// Enable additional attributes
+	cfg := metadata.DefaultMetricsBuilderConfig()
+	cfg.ResourceAttributes.K8sHpaScaletargetrefKind.Enabled = true
+	cfg.ResourceAttributes.K8sHpaScaletargetrefName.Enabled = true
+	cfg.ResourceAttributes.K8sHpaScaletargetrefApiversion.Enabled = true
+
+	mb := metadata.NewMetricsBuilder(cfg, receivertest.NewNopSettings(metadata.Type))
+	RecordMetrics(mb, hpa, ts)
+	m := mb.Emit()
+
+	require.Equal(t, 1, m.ResourceMetrics().Len())
+	rm := m.ResourceMetrics().At(0)
+	assert.Equal(t,
+		map[string]any{
+			"k8s.hpa.uid":                       "test-hpa-1-uid",
+			"k8s.hpa.name":                      "test-hpa-1",
+			"k8s.namespace.name":                "test-namespace",
+			"k8s.hpa.scaletargetref.kind":       "Deployment",
+			"k8s.hpa.scaletargetref.name":       "test-deployment",
+			"k8s.hpa.scaletargetref.apiversion": "apps/v1",
+		},
+		rm.Resource().Attributes().AsRaw())
+}