Add functions to create Prometheus labels and annotations

Author: siegfriedweber

crates/stackable-operator/src/v2/builder.rs

@@ -1,4 +1,5 @@
 pub mod meta;
 pub mod pdb;
 pub mod pod;
+pub mod service;
 pub mod statefulset;

crates/stackable-operator/src/v2/builder/service.rs

@@ -0,0 +1,77 @@
+use crate::{
+    kvp::{Annotations, Labels},
+    v2::types::common::Port,
+};
+
+pub enum Scraping {
+    Enabled,
+    Disabled,
+}
+
+pub enum Scheme {
+    Http,
+    Https,
+}
+
+/// Common labels for Prometheus
+pub fn prometheus_labels(scraping_enabled: &Scraping) -> Labels {
+    Labels::try_from([(
+        "prometheus.io/scrape",
+        // "true" and "false" are valid label values.
+        match scraping_enabled {
+            Scraping::Enabled => "true".to_owned(),
+            Scraping::Disabled => "false".to_owned(),
+        },
+    )])
+    .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>
+///
+/// # Example
+///
+/// ```rust
+/// # use stackable_operator::v2::{
+/// #     builder::service::{Scheme, Scraping, prometheus_annotations},
+/// #     types::common::Port,
+/// # };
+///
+/// prometheus_annotations(
+///     &Scraping::Enabled,
+///     &Scheme::Https,
+///     "/_prometheus/metrics",
+///     &Port(9200),
+/// );
+/// ```
+pub fn prometheus_annotations(
+    scraping_enabled: &Scraping,
+    scheme: &Scheme,
+    path: &str,
+    port: &Port,
+) -> Annotations {
+    // There are no restrictions on annotation values, so it is not necessary to check the given
+    // parameters.
+    Annotations::try_from([
+        ("prometheus.io/path".to_owned(), path.to_owned()),
+        ("prometheus.io/port".to_owned(), port.to_string()),
+        (
+            "prometheus.io/scheme".to_owned(),
+            match scheme {
+                Scheme::Http => "http".to_owned(),
+                Scheme::Https => "https".to_owned(),
+            },
+        ),
+        (
+            "prometheus.io/scrape".to_owned(),
+            match scraping_enabled {
+                Scraping::Enabled => "true".to_owned(),
+                Scraping::Disabled => "false".to_owned(),
+            },
+        ),
+    ])
+    .expect("should be valid annotations")
+}