feat: enable prometheus format in new http tracker core metrics endpoint

Author: josecelano

packages/axum-rest-tracker-api-server/src/v1/context/stats/handlers.rs

@@ -11,7 +11,7 @@ use serde::Deserialize;
 use tokio::sync::RwLock;
 use torrust_rest_tracker_api_core::statistics::services::{get_labeled_metrics, get_metrics};
 
-use super::responses::{labeled_stats_response, metrics_response, stats_response};
+use super::responses::{labeled_metrics_response, labeled_stats_response, metrics_response, stats_response};
 
 #[derive(Deserialize, Debug, Default)]
 #[serde(rename_all = "lowercase")]
@@ -28,7 +28,7 @@ pub struct QueryParams {
     pub format: Option<Format>,
 }
 
-/// It handles the request to get the tracker statistics.
+/// It handles the request to get the tracker global metrics.
 ///
 /// By default it returns a `200` response with the stats in JSON format.
 ///
@@ -58,6 +58,12 @@ pub async fn get_stats_handler(
     }
 }
 
+/// It handles the request to get the tracker extendable metrics.
+///
+/// By default it returns a `200` response with the stats in JSON format.
+///
+/// You can add the GET parameter `format=prometheus` to get the stats in
+/// Prometheus Text Exposition Format.
 #[allow(clippy::type_complexity)]
 pub async fn get_metrics_handler(
     State(state): State<(
@@ -73,7 +79,7 @@ pub async fn get_metrics_handler(
     match params.0.format {
         Some(format) => match format {
             Format::Json => labeled_stats_response(metrics),
-            Format::Prometheus => todo!(),
+            Format::Prometheus => labeled_metrics_response(&metrics),
         },
         None => labeled_stats_response(metrics),
     }

packages/axum-rest-tracker-api-server/src/v1/context/stats/responses.rs

@@ -2,21 +2,27 @@
 //! API context.
 use axum::response::{IntoResponse, Json, Response};
 use torrust_rest_tracker_api_core::statistics::services::{TrackerLabeledMetrics, TrackerMetrics};
+use torrust_tracker_metrics::prometheus::PrometheusSerializable;
 
 use super::resources::{LabeledStats, Stats};
 
-/// `200` response that contains the [`Stats`] resource as json.
-#[must_use]
-pub fn stats_response(tracker_metrics: TrackerMetrics) -> Response {
-    Json(Stats::from(tracker_metrics)).into_response()
-}
-
 /// `200` response that contains the [`LabeledStats`] resource as json.
 #[must_use]
 pub fn labeled_stats_response(tracker_metrics: TrackerLabeledMetrics) -> Response {
     Json(LabeledStats::from(tracker_metrics)).into_response()
 }
 
+#[must_use]
+pub fn labeled_metrics_response(tracker_metrics: &TrackerLabeledMetrics) -> Response {
+    tracker_metrics.metrics.to_prometheus().into_response()
+}
+
+/// `200` response that contains the [`Stats`] resource as json.
+#[must_use]
+pub fn stats_response(tracker_metrics: TrackerMetrics) -> Response {
+    Json(Stats::from(tracker_metrics)).into_response()
+}
+
 /// `200` response that contains the [`Stats`] resource in Prometheus Text Exposition Format .
 #[allow(deprecated)]
 #[must_use]