feat: [torrust#1403] POC. New API endpoint with extendable metrics

This is only a Prood of Concept.

It adds a new  REST API endpoint with a new format for metrics:

URL: http://0.0.0.0:1212/api/v1/metrics?token=MyAccessToken

Sample response:

```json
{
  "labeled_metrics": [
    {
      "metric": {
        "name": "announce_requests_received_total",
        "kind": "counter",
        "value": 1
      },
      "labels": {
        "ip_version": "ipv4",
        "protocol": "http",
        "url": "http://0.0.0.0:7070"
      }
    },
    {
      "metric": {
        "name": "scrape_requests_received_total",
        "kind": "counter",
        "value": 1
      },
      "labels": {
        "ip_version": "ipv4",
        "protocol": "http",
        "url": "http://0.0.0.0:7070"
      }
    }
  ]
}
```

It only supports JSON format for now. It doesn't support prometheus
format like the current stats endpoint:

URL: http://0.0.0.0:1212/api/v1/stats?token=MyAccessToken&format=prometheus

TODO:

- Replace primitive types in the new labeled metrics with new tpyes to
  enforce constraints. For example, metrics names, labels, metric types, etc.
- Inject the rigth URL scheme. It's hardcoded now.
- Implement for UDP metrics. It's only implemented for HTTP tracker metrics. This would require mergin labeled metrics.
- Use a f64 for metric values instead of u64.
- The metric name and label set pair must be unique in the array of
  labeled metrics. Enforce
  constraint.
- Implement versioning. A given API version must contain a set of
  labeled metrics. Clients expects some labeled metrics to be included
in a API version. We need to initialize the array of metrics with all
the expected labeled metrics with the initial value.

Author: josecelano

Cargo.lock

@@ -59,6 +59,7 @@
         "Eray",
         "filesd",
         "flamegraph",
+        "formatjson",
         "Freebox",
         "Frostegård",
         "gecos",

cSpell.json

@@ -9,9 +9,9 @@ use bittorrent_tracker_core::torrent::repository::in_memory::InMemoryTorrentRepo
 use bittorrent_udp_tracker_core::services::banning::BanService;
 use serde::Deserialize;
 use tokio::sync::RwLock;
-use torrust_rest_tracker_api_core::statistics::services::get_metrics;
+use torrust_rest_tracker_api_core::statistics::services::{get_labeled_metrics, get_metrics};
 
-use super::responses::{metrics_response, stats_response};
+use super::responses::{labeled_stats_response, metrics_response, stats_response};
 
 #[derive(Deserialize, Debug, Default)]
 #[serde(rename_all = "lowercase")]
@@ -57,3 +57,24 @@ pub async fn get_stats_handler(
         None => stats_response(metrics),
     }
 }
+
+#[allow(clippy::type_complexity)]
+pub async fn get_metrics_handler(
+    State(state): State<(
+        Arc<InMemoryTorrentRepository>,
+        Arc<RwLock<BanService>>,
+        Arc<bittorrent_http_tracker_core::statistics::repository::Repository>,
+        Arc<torrust_udp_tracker_server::statistics::repository::Repository>,
+    )>,
+    params: Query<QueryParams>,
+) -> Response {
+    let metrics = get_labeled_metrics(state.0.clone(), state.1.clone(), state.2.clone(), state.3.clone()).await;
+
+    match params.0.format {
+        Some(format) => match format {
+            Format::Json => labeled_stats_response(metrics),
+            Format::Prometheus => todo!(),
+        },
+        None => labeled_stats_response(metrics),
+    }
+}

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

@@ -1,7 +1,8 @@
 //! API resources for the [`stats`](crate::v1::context::stats)
 //! API context.
+use bittorrent_http_tracker_core::statistics::metrics::LabeledMetric;
 use serde::{Deserialize, Serialize};
-use torrust_rest_tracker_api_core::statistics::services::TrackerMetrics;
+use torrust_rest_tracker_api_core::statistics::services::{TrackerLabeledMetrics, TrackerMetrics};
 
 /// It contains all the statistics generated by the tracker.
 #[derive(Serialize, Deserialize, Debug, PartialEq, Eq)]
@@ -116,6 +117,22 @@ impl From<TrackerMetrics> for Stats {
     }
 }
 
+/// It contains all the statistics generated by the tracker.
+#[derive(Serialize, Debug, PartialEq, Eq)]
+pub struct LabeledStats {
+    // Extendable metrics
+    labeled_metrics: Vec<LabeledMetric>,
+}
+
+impl From<TrackerLabeledMetrics> for LabeledStats {
+    #[allow(deprecated)]
+    fn from(metrics: TrackerLabeledMetrics) -> Self {
+        Self {
+            labeled_metrics: metrics.labeled_metrics,
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use torrust_rest_tracker_api_core::statistics::metrics::Metrics;

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

@@ -1,16 +1,22 @@
 //! API responses for the [`stats`](crate::v1::context::stats)
 //! API context.
 use axum::response::{IntoResponse, Json, Response};
-use torrust_rest_tracker_api_core::statistics::services::TrackerMetrics;
+use torrust_rest_tracker_api_core::statistics::services::{TrackerLabeledMetrics, TrackerMetrics};
 
-use super::resources::Stats;
+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()
+}
+
 /// `200` response that contains the [`Stats`] resource in Prometheus Text Exposition Format .
 #[allow(deprecated)]
 #[must_use]

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

@@ -9,17 +9,27 @@ use axum::routing::get;
 use axum::Router;
 use torrust_rest_tracker_api_core::container::TrackerHttpApiCoreContainer;
 
-use super::handlers::get_stats_handler;
+use super::handlers::{get_metrics_handler, get_stats_handler};
 
 /// It adds the routes to the router for the [`stats`](crate::v1::context::stats) API context.
 pub fn add(prefix: &str, router: Router, http_api_container: &Arc<TrackerHttpApiCoreContainer>) -> Router {
-    router.route(
-        &format!("{prefix}/stats"),
-        get(get_stats_handler).with_state((
-            http_api_container.tracker_core_container.in_memory_torrent_repository.clone(),
-            http_api_container.ban_service.clone(),
-            http_api_container.http_stats_repository.clone(),
-            http_api_container.udp_server_stats_repository.clone(),
-        )),
-    )
+    router
+        .route(
+            &format!("{prefix}/stats"),
+            get(get_stats_handler).with_state((
+                http_api_container.tracker_core_container.in_memory_torrent_repository.clone(),
+                http_api_container.ban_service.clone(),
+                http_api_container.http_stats_repository.clone(),
+                http_api_container.udp_server_stats_repository.clone(),
+            )),
+        )
+        .route(
+            &format!("{prefix}/metrics"),
+            get(get_metrics_handler).with_state((
+                http_api_container.tracker_core_container.in_memory_torrent_repository.clone(),
+                http_api_container.ban_service.clone(),
+                http_api_container.http_stats_repository.clone(),
+                http_api_container.udp_server_stats_repository.clone(),
+            )),
+        )
 }

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

@@ -20,14 +20,17 @@ bittorrent-primitives = "0.1.0"
 bittorrent-tracker-core = { version = "3.0.0-develop", path = "../tracker-core" }
 criterion = { version = "0.5.1", features = ["async_tokio"] }
 futures = "0"
+serde = "1.0.219"
 thiserror = "2"
 tokio = { version = "1", features = ["macros", "net", "rt-multi-thread", "signal", "sync"] }
 torrust-tracker-configuration = { version = "3.0.0-develop", path = "../configuration" }
 torrust-tracker-primitives = { version = "3.0.0-develop", path = "../primitives" }
 tracing = "0"
 
 [dev-dependencies]
+formatjson = "0.3.1"
 mockall = "0"
+serde_json = "1.0.140"
 torrust-tracker-test-helpers = { version = "3.0.0-develop", path = "../test-helpers" }
 
 [[bench]]