chore: ensure metrics are correctly exposed

CHANGELOG.md

@@ -7,6 +7,7 @@ All notable changes to this project will be documented in this file.
 ### Added
 
 - Helm: Allow Pod `priorityClassName` to be configured ([#633]).
+- Add `prometheus.io/path|port|scheme` annotations to metrics service ([#641]).
 
 ### Fixed
 
@@ -18,6 +19,7 @@ All notable changes to this project will be documented in this file.
 
 [#633]: https://github.com/stackabletech/hive-operator/pull/633
 [#636]: https://github.com/stackabletech/hive-operator/pull/636
+[#641]: https://github.com/stackabletech/hive-operator/pull/641
 
 ## [25.7.0] - 2025-07-23
 

rust/operator-binary/src/service.rs

@@ -3,7 +3,7 @@ use stackable_operator::{
     builder::meta::ObjectMetaBuilder,
     commons::product_image_selection::ResolvedProductImage,
     k8s_openapi::api::core::v1::{Service, ServicePort, ServiceSpec},
-    kvp::{Label, Labels},
+    kvp::{Annotations, Labels},
     role_utils::RoleGroupRef,
 };
 
@@ -90,7 +90,8 @@ pub fn build_rolegroup_metrics_service(
                 &rolegroup.role_group,
             ))
             .context(MetadataBuildSnafu)?
-            .with_label(Label::try_from(("prometheus.io/scrape", "true")).context(LabelBuildSnafu)?)
+            .with_labels(prometheus_labels())
+            .with_annotations(prometheus_annotations())
             .build(),
         spec: Some(ServiceSpec {
             // Internal communication does not need to be exposed
@@ -139,3 +140,23 @@ fn service_ports() -> Vec<ServicePort> {
         ..ServicePort::default()
     }]
 }
+
+/// Common labels for Prometheus
+fn prometheus_labels() -> Labels {
+    Labels::try_from([("prometheus.io/scrape", "true")]).expect("should be a valid label")
+}
+
+/// Common annotations for Prometheus
+///
+/// These annotations can be used in a ServiceMonitor.
+///
+/// see also <https://github.com/prometheus-community/helm-charts/blob/prometheus-27.32.0/charts/prometheus/values.yaml#L983-L1036>
+fn prometheus_annotations() -> Annotations {
+    Annotations::try_from([
+        ("prometheus.io/path".to_owned(), "/metrics".to_owned()),
+        ("prometheus.io/port".to_owned(), METRICS_PORT.to_string()),
+        ("prometheus.io/scheme".to_owned(), "http".to_owned()),
+        ("prometheus.io/scrape".to_owned(), "true".to_owned()),
+    ])
+    .expect("should be valid annotations")
+}