http: Use ExtractParam in NewNormalizeUri (#2245)

This change refactors `http::NormalizeUri` to take an `ExtractParam` for
extracting the default authority, rather than requiring `T:
Param<DefaultAuthority>`. This way, we can remove the wrapper target
type that's used only to temporarily add this `Param` impl.

Author: hawkw

linkerd/app/outbound/src/http/server.rs

@@ -78,11 +78,16 @@ impl<N> Outbound<N> {
                         .push(http_tracing::server(rt.span_sink.clone(), trace_labels()))
                         .push(http::BoxResponse::layer()),
                 )
-                .push_map_target(|Target(t)| t)
                 // Convert origin form HTTP/1 URIs to absolute form for Hyper's
                 // `Client`.
-                .push(http::NewNormalizeUri::layer())
-                .push_map_target(Target)
+                .push(http::NewNormalizeUri::layer_via(|target: &T| {
+                    let addr = match target.param() {
+                        Logical::Route(addr, _) => Addr::from(addr),
+                        Logical::Forward(Remote(ServerAddr(addr)), _) => Addr::from(addr),
+                    };
+
+                    http::normalize_uri::DefaultAuthority(Some(addr.to_http_authority()))
+                }))
                 // Record when a HTTP/1 URI originated in absolute form
                 .push_on_service(http::normalize_uri::MarkAbsoluteForm::layer())
                 .push(svc::ArcNewService::layer())
@@ -119,22 +124,6 @@ impl<N> Outbound<N> {
     }
 }
 
-// === impl Target ===
-
-impl<T> svc::Param<http::normalize_uri::DefaultAuthority> for Target<T>
-where
-    T: svc::Param<Logical>,
-{
-    fn param(&self) -> http::normalize_uri::DefaultAuthority {
-        let addr = match self.0.param() {
-            Logical::Route(addr, _) => Addr::from(addr),
-            Logical::Forward(Remote(ServerAddr(addr)), _) => Addr::from(addr),
-        };
-
-        http::normalize_uri::DefaultAuthority(Some(addr.to_http_authority()))
-    }
-}
-
 // === impl ServerRescue ===
 
 impl ServerRescue {

linkerd/proxy/http/src/normalize_uri.rs

@@ -18,13 +18,14 @@ use super::h1;
 use futures::{future, TryFutureExt};
 use http::uri::Authority;
 use linkerd_error::Error;
-use linkerd_stack::{layer, NewService, Param};
+use linkerd_stack::{layer, ExtractParam, NewService};
 use std::task::{Context, Poll};
 use thiserror::Error;
 use tracing::trace;
 
 #[derive(Clone, Debug)]
-pub struct NewNormalizeUri<N> {
+pub struct NewNormalizeUri<X, N> {
+    extract: X,
     inner: N,
 }
 
@@ -51,25 +52,34 @@ pub struct MarkAbsoluteForm<S> {
 
 // === impl NewNormalizeUri ===
 
-impl<N> NewNormalizeUri<N> {
+impl<N> NewNormalizeUri<(), N> {
     pub fn layer() -> impl layer::Layer<N, Service = Self> + Copy + Clone {
-        layer::mk(Self::new)
+        layer::mk(|inner| Self::new((), inner))
     }
+}
 
-    fn new(inner: N) -> Self {
-        Self { inner }
+impl<X, N> NewNormalizeUri<X, N> {
+    pub fn layer_via(extract: X) -> impl layer::Layer<N, Service = Self> + Clone
+    where
+        X: Clone,
+    {
+        layer::mk(move |inner| Self::new(extract.clone(), inner))
+    }
+
+    fn new(extract: X, inner: N) -> Self {
+        Self { inner, extract }
     }
 }
 
-impl<T, N> NewService<T> for NewNormalizeUri<N>
+impl<T, X, N> NewService<T> for NewNormalizeUri<X, N>
 where
-    T: Param<DefaultAuthority>,
+    X: ExtractParam<DefaultAuthority, T>,
     N: NewService<T>,
 {
     type Service = NormalizeUri<N::Service>;
 
     fn new_service(&self, target: T) -> Self::Service {
-        let DefaultAuthority(default) = target.param();
+        let DefaultAuthority(default) = self.extract.extract_param(&target);
         let inner = self.inner.new_service(target);
         NormalizeUri::new(inner, default)
     }