Add prometheus metrics via metrics-rs

Cargo.toml

@@ -26,6 +26,7 @@ swagger = ["paperclip"]
 rabbit = ["amiquip", "crossbeam-channel"]
 prometheus = []
 tracing = ["dep:tracing", "tracing-actix-web", "tracing-subscriber", "tracing-bunyan-formatter"]
+metrics = ["dep:metrics", "metrics-exporter-prometheus", "lazy_static", "futures-util"]
 
 [dependencies]
 actix = "0.13"
@@ -65,3 +66,8 @@ tracing-actix-web = { version = "0.7.8", optional = true }
 tracing = { version = "0.1.40", features = ["log"], optional = true }
 tracing-subscriber = { version = "0.3.16", features = ["env-filter", "tracing-log"], optional = true }
 tracing-bunyan-formatter = { version = "0.3", optional = true }
+
+metrics = { version = "0.22.1", optional = true }
+metrics-exporter-prometheus = { version = "0.13.1", optional = true }
+lazy_static = { version = "1.4.0", optional = true }
+futures-util = { version = "0.3.30", optional = true }

src/server/builder.rs

@@ -160,6 +160,12 @@ impl<'a> Serwus<'a> {
                 actix_web::web::get().to(super::prometheus::prometheus_stats_handler::<T, D>),
             );
 
+            #[cfg(feature = "metrics")]
+            let app = app.wrap(super::metrics::middleware::Metrics).route(
+                "metrics",
+                actix_web::web::get().to(super::metrics::handler::metrics),
+            );
+
             #[cfg(feature = "swagger")]
             let app = if prod_env {
                 app.wrap_api()

src/server/metrics/handler.rs

@@ -0,0 +1,14 @@
+use actix_web::HttpRequest;
+use lazy_static::lazy_static;
+use metrics_exporter_prometheus::{PrometheusBuilder, PrometheusHandle};
+use paperclip::actix::api_v2_operation;
+
+lazy_static! {
+    pub static ref PROM_HANDLER: PrometheusHandle = PrometheusBuilder::new()
+        .install_recorder()
+        .expect("failed to install recorder");
+}
+
+pub async fn metrics(_: HttpRequest) -> String {
+    PROM_HANDLER.render()
+}

src/server/metrics/middleware.rs

@@ -0,0 +1,74 @@
+use std::{
+    future::{ready, Ready},
+    time::Instant,
+};
+
+use actix_web::{
+    dev::{forward_ready, Service, ServiceRequest, ServiceResponse, Transform},
+    Error,
+};
+use futures_util::future::LocalBoxFuture;
+
+#[derive(Debug, Clone)]
+pub struct Metrics;
+
+impl<S, B> Transform<S, ServiceRequest> for Metrics
+where
+    S: Service<ServiceRequest, Response = ServiceResponse<B>, Error = Error> + 'static,
+    S::Future: 'static,
+    B: 'static,
+{
+    type Response = ServiceResponse<B>;
+    type Error = Error;
+    type InitError = ();
+    type Transform = MetricsMiddleware<S>;
+    type Future = Ready<Result<Self::Transform, Self::InitError>>;
+
+    fn new_transform(&self, service: S) -> Self::Future {
+        ready(Ok(MetricsMiddleware { service }))
+    }
+}
+
+pub struct MetricsMiddleware<S> {
+    service: S,
+}
+
+impl<S, B> Service<ServiceRequest> for MetricsMiddleware<S>
+where
+    S: Service<ServiceRequest, Response = ServiceResponse<B>, Error = Error> + 'static,
+    S::Future: 'static,
+    B: 'static,
+{
+    type Response = ServiceResponse<B>;
+    type Error = Error;
+    type Future = LocalBoxFuture<'static, Result<Self::Response, Self::Error>>;
+
+    forward_ready!(service);
+
+    fn call(&self, req: ServiceRequest) -> Self::Future {
+        let start = Instant::now();
+        let path = req.path().to_owned();
+        let method = req.method().to_string();
+
+        let fut = self.service.call(req);
+
+        Box::pin(async move {
+            let response = fut.await;
+
+            let latency = start.elapsed().as_secs_f64();
+            let status = response
+                .as_ref()
+                .map(|r| r.status())
+                .unwrap_or_else(|e| e.as_response_error().status_code())
+                .as_u16()
+                .to_string();
+
+            let labels = [("method", method), ("path", path), ("status", status)];
+
+            metrics::counter!("http_requests_total", &labels).increment(1);
+            metrics::histogram!("http_requests_duration_seconds", &labels).record(latency);
+
+            response
+        })
+    }
+}

src/server/metrics/mod.rs

@@ -0,0 +1,2 @@
+pub mod handler;
+pub mod middleware;

src/server/mod.rs

@@ -5,6 +5,8 @@ mod builder;
 pub mod json_error;
 #[cfg(feature = "prometheus")]
 pub mod prometheus;
+#[cfg(feature = "metrics")]
+pub mod metrics;
 pub mod stats;
 
 use actix_cors::Cors;