http: Parameterize authority overriding (#946)

The authority override module still uses a dedicated trait,
`CanOverrideAuthority`. This change replaces this trait with a newtype,
`AuthorityOverride`, which is provided via `Param`.

Author: olix0r

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

@@ -135,9 +135,12 @@ impl Param<Option<SessionProtocol>> for Endpoint {
     }
 }
 
-impl CanOverrideAuthority for Endpoint {
-    fn override_authority(&self) -> Option<uri::Authority> {
-        self.metadata.authority_override().cloned()
+impl Param<Option<AuthorityOverride>> for Endpoint {
+    fn param(&self) -> Option<AuthorityOverride> {
+        self.metadata
+            .authority_override()
+            .cloned()
+            .map(AuthorityOverride)
     }
 }
 

linkerd/proxy/http/src/lib.rs

@@ -30,7 +30,7 @@ pub use self::{
     glue::{HyperServerSvc, UpgradeBody},
     header_from_target::NewHeaderFromTarget,
     normalize_uri::{MarkAbsoluteForm, NewNormalizeUri},
-    override_authority::{CanOverrideAuthority, NewOverrideAuthority},
+    override_authority::{AuthorityOverride, NewOverrideAuthority},
     retain::Retain,
     server::NewServeHttp,
     timeout::MakeTimeoutLayer,

linkerd/proxy/http/src/override_authority.rs

@@ -1,16 +1,15 @@
 use super::h1;
 use http::{self, header::AsHeaderName, uri::Authority};
-use linkerd_stack::{layer, NewService};
+use linkerd_stack::{layer, NewService, Param};
 use std::{
     fmt,
     sync::Arc,
     task::{Context, Poll},
 };
 use tracing::debug;
 
-pub trait CanOverrideAuthority {
-    fn override_authority(&self) -> Option<Authority>;
-}
+#[derive(Clone, Debug)]
+pub struct AuthorityOverride(pub Authority);
 
 #[derive(Clone, Debug)]
 pub struct NewOverrideAuthority<H, M> {
@@ -41,7 +40,7 @@ impl<H: Clone, N> NewOverrideAuthority<H, N> {
 
 impl<H, T, M> NewService<T> for NewOverrideAuthority<H, M>
 where
-    T: CanOverrideAuthority + Clone + Send + Sync + 'static,
+    T: Param<Option<AuthorityOverride>>,
     M: NewService<T>,
     H: AsHeaderName + Clone,
 {
@@ -50,7 +49,7 @@ where
     #[inline]
     fn new_service(&mut self, t: T) -> Self::Service {
         OverrideAuthority {
-            authority: t.override_authority(),
+            authority: t.param().map(|AuthorityOverride(a)| a),
             headers_to_strip: self.headers_to_strip.clone(),
             inner: self.inner.new_service(t),
         }