Fix connection counter leak when response timeout

src/middleware/connection_counter.rs

@@ -15,6 +15,7 @@ use axum::{
 use futures::future::BoxFuture;
 use http_body::{Frame, SizeHint};
 use pin_project_lite::pin_project;
+use scopeguard::{guard, ScopeGuard};
 use tokio::sync::mpsc::Sender;
 use tower::{Layer, Service};
 
@@ -81,11 +82,16 @@ where
         if counter.fetch_add(1, Ordering::Relaxed) > (self.data.settings.max_connection() as f64 * 0.8).ceil() as u64 {
             let _ = self.data.command_channel.try_send(Command::Overload);
         };
+        let guard = guard(counter, move |counter| {
+            counter.fetch_sub(1, Ordering::Relaxed);
+        });
 
         let fut = self.service.call(req);
 
         Box::pin(async move {
-            match fut.await {
+            let res = fut.await;
+            let counter = ScopeGuard::into_inner(guard); // Cancel counter guard
+            match res {
                 Ok(res) => Ok(res.map(|body| ConnectionCounterFinalizer { body, counter })),
                 Err(err) => {
                     counter.fetch_sub(1, Ordering::Relaxed);