Improve performance of BoxRoute (#339)

* Improve performance of `BoxRoute`

This is based on #315 but slightly shorter.

It removes the need for a `tower::buffer::Buffer` in `BoxRoute` which
improves performance.

* changelog

Co-authored-by: Programatik <[email protected]>

src/routing/mod.rs

@@ -3,7 +3,7 @@
 use self::future::{BoxRouteFuture, EmptyRouterFuture, NestedFuture, RouteFuture};
 use crate::{
     body::{box_body, BoxBody},
-    buffer::MpscBuffer,
+    clone_box_service::CloneBoxService,
     extract::{
         connect_info::{Connected, IntoMakeServiceWithConnectInfo},
         OriginalUri,
@@ -24,10 +24,7 @@ use std::{
     sync::Arc,
     task::{Context, Poll},
 };
-use tower::{
-    util::{BoxService, ServiceExt},
-    ServiceBuilder,
-};
+use tower::{util::ServiceExt, ServiceBuilder};
 use tower_http::map_response_body::MapResponseBodyLayer;
 use tower_layer::Layer;
 use tower_service::Service;
@@ -256,7 +253,7 @@ impl<S> Router<S> {
     /// routes.
     pub fn boxed<ReqBody, ResBody>(self) -> Router<BoxRoute<ReqBody, S::Error>>
     where
-        S: Service<Request<ReqBody>, Response = Response<ResBody>> + Send + 'static,
+        S: Service<Request<ReqBody>, Response = Response<ResBody>> + Clone + Send + Sync + 'static,
         S::Error: Into<BoxError> + Send,
         S::Future: Send,
         ReqBody: Send + 'static,
@@ -266,8 +263,7 @@ impl<S> Router<S> {
         self.map(|svc| {
             ServiceBuilder::new()
                 .layer_fn(BoxRoute)
-                .layer_fn(MpscBuffer::new)
-                .layer(BoxService::layer())
+                .layer_fn(CloneBoxService::new)
                 .layer(MapResponseBodyLayer::new(box_body))
                 .service(svc)
         })
@@ -834,7 +830,7 @@ type Captures = Vec<(String, String)>;
 ///
 /// See [`Router::boxed`] for more details.
 pub struct BoxRoute<B = crate::body::Body, E = Infallible>(
-    MpscBuffer<BoxService<Request<B>, Response<BoxBody>, E>, Request<B>>,
+    CloneBoxService<Request<B>, Response<BoxBody>, E>,
 );
 
 impl<B, E> Clone for BoxRoute<B, E> {