feat(starknet_monitoring_endpoint): add metrics endpoint

crates/starknet_monitoring_endpoint/Cargo.toml

@@ -14,6 +14,7 @@ workspace = true
 [dependencies]
 axum.workspace = true
 hyper = { workspace = true }
+metrics-exporter-prometheus.workspace = true
 papyrus_config.workspace = true
 serde.workspace = true
 starknet_sequencer_infra.workspace = true
@@ -23,6 +24,7 @@ tracing.workspace = true
 validator.workspace = true
 
 [dev-dependencies]
+metrics.workspace = true
 pretty_assertions.workspace = true
 tokio.workspace = true
 tower.workspace = true

crates/starknet_monitoring_endpoint/src/monitoring_endpoint.rs

@@ -2,9 +2,11 @@ use std::any::type_name;
 use std::net::SocketAddr;
 
 use axum::http::StatusCode;
+use axum::response::{IntoResponse, Response};
 use axum::routing::get;
 use axum::{async_trait, Router, Server};
 use hyper::Error;
+use metrics_exporter_prometheus::PrometheusHandle;
 use starknet_sequencer_infra::component_definitions::ComponentStarter;
 use starknet_sequencer_infra::errors::ComponentError;
 use tracing::{info, instrument};
@@ -19,15 +21,17 @@ pub(crate) const MONITORING_PREFIX: &str = "monitoring";
 pub(crate) const ALIVE: &str = "alive";
 pub(crate) const READY: &str = "ready";
 pub(crate) const VERSION: &str = "nodeVersion";
+pub(crate) const METRICS: &str = "metrics";
 
 pub struct MonitoringEndpoint {
     config: MonitoringEndpointConfig,
     version: &'static str,
+    prometheus_handle: Option<PrometheusHandle>,
 }
 
 impl MonitoringEndpoint {
     pub fn new(config: MonitoringEndpointConfig, version: &'static str) -> Self {
-        MonitoringEndpoint { config, version }
+        MonitoringEndpoint { config, version, prometheus_handle: None }
     }
 
     #[instrument(
@@ -41,13 +45,13 @@ impl MonitoringEndpoint {
         let MonitoringEndpointConfig { ip, port } = self.config;
         let endpoint_addr = SocketAddr::new(ip, port);
 
-        let app = self.app();
+        let app = self.app(self.prometheus_handle.clone());
         info!("MonitoringEndpoint running using socket: {}", endpoint_addr);
 
         Server::bind(&endpoint_addr).serve(app.into_make_service()).await
     }
 
-    fn app(&self) -> Router {
+    fn app(&self, prometheus_handle: Option<PrometheusHandle>) -> Router {
         let version = self.version.to_string();
 
         Router::new()
@@ -63,6 +67,10 @@ impl MonitoringEndpoint {
                 format!("/{MONITORING_PREFIX}/{VERSION}").as_str(),
                 get(move || async { version }),
             )
+            .route(
+                format!("/{MONITORING_PREFIX}/{METRICS}").as_str(),
+                get(move || metrics(prometheus_handle)),
+            )
     }
 }
 
@@ -80,3 +88,14 @@ impl ComponentStarter for MonitoringEndpoint {
         self.run().await.map_err(|_| ComponentError::InternalComponentError)
     }
 }
+
+/// Returns prometheus metrics.
+/// In case the node doesn’t collect metrics returns an empty response with status code 405: method
+/// not allowed.
+#[instrument(level = "debug", ret, skip(prometheus_handle))]
+async fn metrics(prometheus_handle: Option<PrometheusHandle>) -> Response {
+    match prometheus_handle {
+        Some(handle) => handle.render().into_response(),
+        None => StatusCode::METHOD_NOT_ALLOWED.into_response(),
+    }
+}

crates/starknet_monitoring_endpoint/src/monitoring_endpoint_test.rs

@@ -5,6 +5,8 @@ use axum::response::Response;
 use axum::Router;
 use hyper::body::to_bytes;
 use hyper::Client;
+use metrics::{absolute_counter, describe_counter, register_counter};
+use metrics_exporter_prometheus::PrometheusBuilder;
 use pretty_assertions::assert_eq;
 use tokio::spawn;
 use tokio::task::yield_now;
@@ -32,7 +34,7 @@ async fn request_app(app: Router, method: &str) -> Response {
 
 #[tokio::test]
 async fn test_node_version() {
-    let response = request_app(setup_monitoring_endpoint().app(), VERSION).await;
+    let response = request_app(setup_monitoring_endpoint().app(None), VERSION).await;
     assert_eq!(response.status(), StatusCode::OK);
 
     let body = to_bytes(response.into_body()).await.unwrap();
@@ -41,16 +43,47 @@ async fn test_node_version() {
 
 #[tokio::test]
 async fn test_alive() {
-    let response = request_app(setup_monitoring_endpoint().app(), ALIVE).await;
+    let response = request_app(setup_monitoring_endpoint().app(None), ALIVE).await;
     assert_eq!(response.status(), StatusCode::OK);
 }
 
 #[tokio::test]
 async fn test_ready() {
-    let response = request_app(setup_monitoring_endpoint().app(), READY).await;
+    let response = request_app(setup_monitoring_endpoint().app(None), READY).await;
     assert_eq!(response.status(), StatusCode::OK);
 }
 
+#[tokio::test]
+async fn with_metrics() {
+    let app =
+        setup_monitoring_endpoint().app(Some(PrometheusBuilder::new().install_recorder().unwrap()));
+
+    // Register a metric.
+    let metric_name = "metric_name";
+    let metric_help = "metric_help";
+    let metric_value = 8224;
+    register_counter!(metric_name);
+    describe_counter!(metric_name, metric_help);
+    absolute_counter!(metric_name, metric_value);
+
+    let response = request_app(app, crate::monitoring_endpoint::METRICS).await;
+    assert_eq!(response.status(), StatusCode::OK);
+    let body_bytes = hyper::body::to_bytes(response.into_body()).await.unwrap();
+    let body_string = String::from_utf8(body_bytes.to_vec()).unwrap();
+    let expected_prefix = format!(
+        "# HELP {metric_name} {metric_help}\n# TYPE {metric_name} counter\n{metric_name} \
+         {metric_value}\n\n"
+    );
+    assert!(body_string.starts_with(&expected_prefix));
+}
+
+#[tokio::test]
+async fn without_metrics() {
+    let app = setup_monitoring_endpoint().app(None);
+    let response = request_app(app, crate::monitoring_endpoint::METRICS).await;
+    assert_eq!(response.status(), StatusCode::METHOD_NOT_ALLOWED);
+}
+
 #[tokio::test]
 async fn test_endpoint_as_server() {
     spawn(async move { setup_monitoring_endpoint().run().await });