outbound: Restore spawn-ready (#679)

The spawn-ready layer was removed in 1382e32; but this means that
endpoint-level services aren't necessarily driven to readiness. This
can manifest in TLS detection timeouts, since a client may not be driven
through the TLS handshake.

This change removes the `push_spawn_ready` helper, because it's really a
`push_make_spawn_ready` and the make layer is totally superfluous.

Author: olix0r

linkerd/app/core/src/svc.rs

@@ -13,7 +13,7 @@ use std::time::Duration;
 use tower::layer::util::{Identity, Stack as Pair};
 pub use tower::layer::Layer;
 pub use tower::make::MakeService;
-use tower::spawn_ready::SpawnReadyLayer;
+pub use tower::spawn_ready::SpawnReady;
 pub use tower::util::{Either, Oneshot};
 pub use tower::{service_fn as mk, Service, ServiceExt};
 
@@ -99,10 +99,6 @@ impl<L> Layers<L> {
         self.push(stack::OnResponseLayer::new(layer))
     }
 
-    pub fn push_spawn_ready(self) -> Layers<Pair<L, SpawnReadyLayer>> {
-        self.push(SpawnReadyLayer::new())
-    }
-
     pub fn push_concurrency_limit(self, max: usize) -> Layers<Pair<L, concurrency_limit::Layer>> {
         self.push(concurrency_limit::Layer::new(max))
     }
@@ -209,10 +205,6 @@ impl<S> Stack<S> {
         self.push(stack::OnResponseLayer::new(layer))
     }
 
-    pub fn push_spawn_ready(self) -> Stack<tower::spawn_ready::MakeSpawnReady<S>> {
-        self.push(SpawnReadyLayer::new())
-    }
-
     pub fn push_concurrency_limit(
         self,
         max: usize,

linkerd/app/outbound/src/lib.rs

@@ -292,7 +292,7 @@ impl Config {
         let discover = svc::layers()
             .push(discover::resolve(map_endpoint::Resolve::new(
                 endpoint::FromMetadata,
-                resolve.clone(),
+                resolve,
             )))
             .push(discover::buffer(1_000, cache_max_idle_age));
 
@@ -301,6 +301,7 @@ impl Config {
             .check_new_service::<HttpEndpoint, http::Request<http::boxed::Payload>>()
             .push_on_response(
                 svc::layers()
+                    .push(svc::layer::mk(svc::SpawnReady::new))
                     .push(metrics.stack.layer(stack_labels("balance.endpoint")))
                     .box_http_request(),
             )
@@ -332,6 +333,7 @@ impl Config {
         let logical = concrete
             // Uses the split-provided target `Addr` to build a concrete target.
             .push_map_target(HttpConcrete::from)
+            .push_on_response(svc::layers().push(svc::layer::mk(svc::SpawnReady::new)))
             .push(profiles::split::layer())
             // Drives concrete stacks to readiness and makes the split
             // cloneable, as required by the retry middleware.