feat: Add pod affinity/anti-affinity metrics for deployments

docs/metrics/workload/deployment-metrics.md

@@ -1,7 +1,7 @@
 # Deployment Metrics
 
 | Metric name                                                 | Metric type | Description                                                                                                                             | Labels/tags                                                                                                                                                                 | Status       |
-| ----------------------------------------------------------- | ----------- | --------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------ |
+|-------------------------------------------------------------|-------------|-----------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------|
 | kube_deployment_annotations                                 | Gauge       | Kubernetes annotations converted to Prometheus labels controlled via [--metric-annotations-allowlist](../../developer/cli-arguments.md) | `deployment`=&lt;deployment-name&gt; <br> `namespace`=&lt;deployment-namespace&gt; <br> `annotation_DEPLOYMENT_ANNOTATION`=&lt;DEPLOYMENT_ANNOTATION&gt;                    | EXPERIMENTAL |
 | kube_deployment_status_replicas                             | Gauge       | The number of replicas per deployment.                                                                                                 | `deployment`=&lt;deployment-name&gt; <br> `namespace`=&lt;deployment-namespace&gt;                                                                                          | STABLE       |
 | kube_deployment_status_replicas_ready                       | Gauge       | The number of ready replicas per deployment.                                                                                           | `deployment`=&lt;deployment-name&gt; <br> `namespace`=&lt;deployment-namespace&gt;                                                                                          | STABLE       |
@@ -12,9 +12,10 @@
 | kube_deployment_status_condition                            | Gauge       | The current status conditions of a deployment.                                                                                         | `deployment`=&lt;deployment-name&gt; <br> `namespace`=&lt;deployment-namespace&gt; <br> `reason`=&lt;deployment-transition-reason&gt; <br> `condition`=&lt;deployment-condition&gt; <br> `status`=&lt;true\|false\|unknown&gt; | STABLE       |
 | kube_deployment_spec_replicas                               | Gauge       | Number of desired pods for a deployment.                                                                                               | `deployment`=&lt;deployment-name&gt; <br> `namespace`=&lt;deployment-namespace&gt;                                                                                          | STABLE       |
 | kube_deployment_spec_paused                                 | Gauge       | Whether the deployment is paused and will not be processed by the deployment controller.                                               | `deployment`=&lt;deployment-name&gt; <br> `namespace`=&lt;deployment-namespace&gt;                                                                                          | STABLE       |
+| kube_deployment_spec_affinity                               | Gauge       | Pod affinity and anti-affinity rules defined in the deployment's pod template specification                                             | `deployment`=&lt;deployment-name&gt; <br> `namespace`=&lt;deployment-namespace&gt; <br> `affinity`=&lt;podaffinity\|podantiaffinity&gt; <br> `type`=&lt;requiredDuringSchedulingIgnoredDuringExecution\|preferredDuringSchedulingIgnoredDuringExecution&gt; <br> `topology_key`=&lt;topology-key&gt; <br> `label_selector`=&lt;selector-string&gt; <br> `namespace_selector`=&lt;namespace-selector-string&gt; <br> `namespaces`=&lt;comma-separated-namespaces&gt; | ALPHA |
 | kube_deployment_spec_strategy_rollingupdate_max_unavailable | Gauge       | Maximum number of unavailable replicas during a rolling update of a deployment.                                                        | `deployment`=&lt;deployment-name&gt; <br> `namespace`=&lt;deployment-namespace&gt;                                                                                          | STABLE       |
 | kube_deployment_spec_strategy_rollingupdate_max_surge       | Gauge       | Maximum number of replicas that can be scheduled above the desired number of replicas during a rolling update of a deployment.        | `deployment`=&lt;deployment-name&gt; <br> `namespace`=&lt;deployment-namespace&gt;                                                                                          | STABLE       |
 | kube_deployment_metadata_generation                         | Gauge       | Sequence number representing a specific generation of the desired state.                                                               | `deployment`=&lt;deployment-name&gt; <br> `namespace`=&lt;deployment-namespace&gt;                                                                                          | STABLE       |
 | kube_deployment_labels                                      | Gauge       | Kubernetes labels converted to Prometheus labels controlled via [--metric-labels-allowlist](../../developer/cli-arguments.md)           | `deployment`=&lt;deployment-name&gt; <br> `namespace`=&lt;deployment-namespace&gt; <br> `label_DEPLOYMENT_LABEL`=&lt;DEPLOYMENT_LABEL&gt;                                   | STABLE       |
 | kube_deployment_created                                     | Gauge       | Unix creation timestamp                                                                                                                 | `deployment`=&lt;deployment-name&gt; <br> `namespace`=&lt;deployment-namespace&gt;                                                                                          | STABLE       |
-| kube_deployment_deletion_timestamp                          | Gauge       | Unix deletion timestamp                                                                                                                 | `deployment`=&lt;deployment-name&gt; <br> `namespace`=&lt;deployment-namespace&gt;                                                                                          | EXPIREMENTAL |
+| kube_deployment_deletion_timestamp                          | Gauge       | Unix deletion timestamp                                                                                                                 | `deployment`=&lt;deployment-name&gt; <br> `namespace`=&lt;deployment-namespace&gt;                                                                                          | EXPERIMENTAL |

internal/store/deployment.go

@@ -18,6 +18,7 @@ package store
 
 import (
 	"context"
+	"strings"
 
 	basemetrics "k8s.io/component-base/metrics"
 
@@ -289,6 +290,15 @@ func deploymentMetricFamilies(allowAnnotationsList, allowLabelsList []string) []
 				}
 			}),
 		),
+		*generator.NewFamilyGeneratorWithStability(
+			"kube_deployment_spec_affinity",
+			"Pod affinity and anti-affinity rules defined in the deployment's pod template specification.",
+			metric.Gauge,
+			basemetrics.ALPHA,
+			"",
+			wrapDeploymentFunc(generateDeploymentAffinityMetrics),
+		),
+
 		*generator.NewFamilyGeneratorWithStability(
 			"kube_deployment_metadata_generation",
 			"Sequence number representing a specific generation of the desired state.",
@@ -398,3 +408,74 @@ func createDeploymentListWatch(kubeClient clientset.Interface, ns string, fieldS
 		},
 	}
 }
+func generateDeploymentAffinityMetrics(d *v1.Deployment) *metric.Family {
+	var metrics []*metric.Metric
+
+	if d.Spec.Template.Spec.Affinity == nil {
+		return &metric.Family{Metrics: metrics}
+	}
+
+	// Handle pod affinity rules
+	if d.Spec.Template.Spec.Affinity.PodAffinity != nil {
+		// Required affinity rules
+		for _, rule := range d.Spec.Template.Spec.Affinity.PodAffinity.RequiredDuringSchedulingIgnoredDuringExecution {
+			labelSelector := formatLabelSelector(rule.LabelSelector)
+			namespaceSelector := formatLabelSelector(rule.NamespaceSelector)
+			namespaces := strings.Join(rule.Namespaces, ",")
+			metrics = append(metrics, &metric.Metric{
+				LabelKeys:   []string{"affinity", "type", "topology_key", "label_selector", "namespace_selector", "namespaces"},
+				LabelValues: []string{"podaffinity", "requiredDuringSchedulingIgnoredDuringExecution", rule.TopologyKey, labelSelector, namespaceSelector, namespaces},
+				Value:       1,
+			})
+		}
+
+		// Preferred affinity rules
+		for _, rule := range d.Spec.Template.Spec.Affinity.PodAffinity.PreferredDuringSchedulingIgnoredDuringExecution {
+			labelSelector := formatLabelSelector(rule.PodAffinityTerm.LabelSelector)
+			namespaceSelector := formatLabelSelector(rule.PodAffinityTerm.NamespaceSelector)
+			namespaces := strings.Join(rule.PodAffinityTerm.Namespaces, ",")
+			metrics = append(metrics, &metric.Metric{
+				LabelKeys:   []string{"affinity", "type", "topology_key", "label_selector", "namespace_selector", "namespaces"},
+				LabelValues: []string{"podaffinity", "preferredDuringSchedulingIgnoredDuringExecution", rule.PodAffinityTerm.TopologyKey, labelSelector, namespaceSelector, namespaces},
+				Value:       1,
+			})
+		}
+	}
+
+	// Handle pod anti-affinity rules
+	if d.Spec.Template.Spec.Affinity.PodAntiAffinity != nil {
+		// Required anti-affinity rules
+		for _, rule := range d.Spec.Template.Spec.Affinity.PodAntiAffinity.RequiredDuringSchedulingIgnoredDuringExecution {
+			labelSelector := formatLabelSelector(rule.LabelSelector)
+			namespaceSelector := formatLabelSelector(rule.NamespaceSelector)
+			namespaces := strings.Join(rule.Namespaces, ",")
+			metrics = append(metrics, &metric.Metric{
+				LabelKeys:   []string{"affinity", "type", "topology_key", "label_selector", "namespace_selector", "namespaces"},
+				LabelValues: []string{"podantiaffinity", "requiredDuringSchedulingIgnoredDuringExecution", rule.TopologyKey, labelSelector, namespaceSelector, namespaces},
+				Value:       1,
+			})
+		}
+
+		// Preferred anti-affinity rules
+		for _, rule := range d.Spec.Template.Spec.Affinity.PodAntiAffinity.PreferredDuringSchedulingIgnoredDuringExecution {
+			labelSelector := formatLabelSelector(rule.PodAffinityTerm.LabelSelector)
+			namespaceSelector := formatLabelSelector(rule.PodAffinityTerm.NamespaceSelector)
+			namespaces := strings.Join(rule.PodAffinityTerm.Namespaces, ",")
+			metrics = append(metrics, &metric.Metric{
+				LabelKeys:   []string{"affinity", "type", "topology_key", "label_selector", "namespace_selector", "namespaces"},
+				LabelValues: []string{"podantiaffinity", "preferredDuringSchedulingIgnoredDuringExecution", rule.PodAffinityTerm.TopologyKey, labelSelector, namespaceSelector, namespaces},
+				Value:       1,
+			})
+		}
+	}
+
+	return &metric.Family{Metrics: metrics}
+}
+
+// formatLabelSelector converts a LabelSelector to a string representation
+func formatLabelSelector(selector *metav1.LabelSelector) string {
+	if selector == nil {
+		return ""
+	}
+	return metav1.FormatLabelSelector(selector)
+}