Changed prometheus metrics feature as optional

meilisearch-http/src/route_metrics.rs

@@ -0,0 +1,75 @@
+use std::future::{ready, Ready};
+
+use actix_web::{
+    dev::{self, Service, ServiceRequest, ServiceResponse, Transform},
+    Error,
+};
+use futures_util::future::LocalBoxFuture;
+use prometheus::HistogramTimer;
+
+pub struct RouteMetrics;
+
+// Middleware factory is `Transform` trait from actix-service crate
+// `S` - type of the next service
+// `B` - type of response's body
+impl<S, B> Transform<S, ServiceRequest> for RouteMetrics
+where
+    S: Service<ServiceRequest, Response = ServiceResponse<B>, Error = Error>,
+    S::Future: 'static,
+    B: 'static,
+{
+    type Response = ServiceResponse<B>;
+    type Error = Error;
+    type InitError = ();
+    type Transform = RouteMetricsMiddleware<S>;
+    type Future = Ready<Result<Self::Transform, Self::InitError>>;
+
+    fn new_transform(&self, service: S) -> Self::Future {
+        ready(Ok(RouteMetricsMiddleware { service }))
+    }
+}
+
+pub struct RouteMetricsMiddleware<S> {
+    service: S,
+}
+
+impl<S, B> Service<ServiceRequest> for RouteMetricsMiddleware<S>
+where
+    S: Service<ServiceRequest, Response = ServiceResponse<B>, Error = Error>,
+    S::Future: 'static,
+    B: 'static,
+{
+    type Response = ServiceResponse<B>;
+    type Error = Error;
+    type Future = LocalBoxFuture<'static, Result<Self::Response, Self::Error>>;
+
+    dev::forward_ready!(service);
+
+    fn call(&self, req: ServiceRequest) -> Self::Future {
+        let mut histogram_timer: Option<HistogramTimer> = None;
+        let request_path = req.path();
+        let is_registered_resource = req.resource_map().has_resource(request_path);
+        if is_registered_resource {
+            let request_method = req.method().to_string();
+            histogram_timer = Some(
+                crate::metrics::HTTP_RESPONSE_TIME_SECONDS
+                    .with_label_values(&[&request_method, request_path])
+                    .start_timer(),
+            );
+            crate::metrics::HTTP_REQUESTS_TOTAL
+                .with_label_values(&[&request_method, request_path])
+                .inc();
+        }
+
+        let fut = self.service.call(req);
+
+        Box::pin(async move {
+            let res = fut.await?;
+
+            if let Some(histogram_timer) = histogram_timer {
+                histogram_timer.observe_duration();
+            };
+            Ok(res)
+        })
+    }
+}