chore: ensure metrics are correctly exposed (#698)

* add prometheus annotations to metrics service

* clippy

* adapted changelog

* fix copy paste

Author: maltesander

CHANGELOG.md

@@ -13,6 +13,7 @@
   - `EOS_CHECK_MODE` (`--eos-check-mode`) to set the EoS check mode. Currently, only "offline" is supported.
   - `EOS_INTERVAL` (`--eos-interval`) to set the interval in which the operator checks if it is EoS.
   - `EOS_DISABLED` (`--eos-disabled`) to disable the EoS checker completely.
+- Add `prometheus.io/path|port|scheme` annotations to metrics service ([#698]).
 
 ### Changed
 
@@ -50,6 +51,7 @@
 [#692]: https://github.com/stackabletech/airflow-operator/pull/692
 [#695]: https://github.com/stackabletech/airflow-operator/pull/695
 [#696]: https://github.com/stackabletech/airflow-operator/pull/696
+[#698]: https://github.com/stackabletech/airflow-operator/pull/698
 
 ## [25.7.0] - 2025-07-23
 

rust/operator-binary/src/service.rs

@@ -4,7 +4,7 @@ use snafu::{ResultExt, Snafu};
 use stackable_operator::{
     builder::meta::ObjectMetaBuilder,
     k8s_openapi::api::core::v1::{Service, ServicePort, ServiceSpec},
-    kvp::{Label, ObjectLabels},
+    kvp::{Annotations, Labels, ObjectLabels},
     role_utils::RoleGroupRef,
 };
 
@@ -78,17 +78,15 @@ pub fn build_rolegroup_metrics_service(
 ) -> Result<Service, Error> {
     let ports = metrics_service_ports();
 
-    let prometheus_label =
-        Label::try_from(("prometheus.io/scrape", "true")).context(LabelBuildSnafu)?;
-
     let metadata = ObjectMetaBuilder::new()
         .name_and_namespace(airflow)
         .name(rolegroup_metrics_service_name(&rolegroup_ref.object_name()))
         .ownerreference_from_resource(airflow, None, Some(true))
         .context(ObjectMissingMetadataForOwnerRefSnafu)?
         .with_recommended_labels(object_labels)
         .context(MetadataBuildSnafu)?
-        .with_label(prometheus_label)
+        .with_labels(prometheus_labels())
+        .with_annotations(prometheus_annotations())
         .build();
 
     let service_spec = ServiceSpec {
@@ -145,3 +143,23 @@ fn metrics_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")
+}