feat(metrics): add real-time throughput sampling and byte-counting metrics

rust/crates/rustproxy-http/src/proxy_service.rs

@@ -21,6 +21,7 @@ use tracing::{debug, error, info, warn};
 use rustproxy_routing::RouteManager;
 use rustproxy_metrics::MetricsCollector;
 
+use crate::counting_body::{CountingBody, Direction};
 use crate::request_filter::RequestFilter;
 use crate::response_filter::ResponseFilter;
 use crate::upstream_selector::UpstreamSelector;
@@ -345,8 +346,16 @@ impl HttpProxyService {
             }
         }
 
+        // Wrap the request body in CountingBody to track bytes_in
+        let counting_req_body = CountingBody::new(
+            body,
+            Arc::clone(&self.metrics),
+            route_id.map(|s| s.to_string()),
+            Direction::In,
+        );
+
         // Stream the request body through to upstream
-        let upstream_req = upstream_req.body(body).unwrap();
+        let upstream_req = upstream_req.body(counting_req_body).unwrap();
 
         let upstream_response = match sender.send_request(upstream_req).await {
             Ok(resp) => resp,
@@ -401,8 +410,16 @@ impl HttpProxyService {
             }
         }
 
+        // Wrap the request body in CountingBody to track bytes_in
+        let counting_req_body = CountingBody::new(
+            body,
+            Arc::clone(&self.metrics),
+            route_id.map(|s| s.to_string()),
+            Direction::In,
+        );
+
         // Stream the request body through to upstream
-        let upstream_req = upstream_req.body(body).unwrap();
+        let upstream_req = upstream_req.body(counting_req_body).unwrap();
 
         let upstream_response = match sender.send_request(upstream_req).await {
             Ok(resp) => resp,
@@ -417,6 +434,10 @@ impl HttpProxyService {
     }
 
     /// Build the client-facing response from an upstream response, streaming the body.
+    ///
+    /// The response body is wrapped in a `CountingBody` that counts bytes as they
+    /// stream from upstream to client. When the body is fully consumed (or dropped),
+    /// it reports byte counts to the metrics collector and calls `connection_closed`.
     async fn build_streaming_response(
         &self,
         upstream_response: Response<Incoming>,
@@ -433,10 +454,22 @@ impl HttpProxyService {
             ResponseFilter::apply_headers(route, headers, None);
         }
 
+        // Wrap the response body in CountingBody to track bytes_out.
+        // CountingBody will report bytes and we close the connection metric
+        // after the body stream completes (not before it even starts).
+        let counting_body = CountingBody::new(
+            resp_body,
+            Arc::clone(&self.metrics),
+            route_id.map(|s| s.to_string()),
+            Direction::Out,
+        );
+
+        // Close the connection metric now — the HTTP request/response cycle is done
+        // from the proxy's perspective once we hand the streaming body to hyper.
+        // Bytes will still be counted as they flow.
         self.metrics.connection_closed(route_id);
 
-        // Stream the response body directly from upstream to client
-        let body: BoxBody<Bytes, hyper::Error> = BoxBody::new(resp_body);
+        let body: BoxBody<Bytes, hyper::Error> = BoxBody::new(counting_body);
 
         Ok(response.body(body).unwrap())
     }