Remove the labels::Direction type (#72)

Following #67 and #68, the `labels::Direction` type can be replaced with
an `impl FmtLabels for ctx::Proxy`.

src/ctx/mod.rs

@@ -8,6 +8,8 @@ pub mod transport;
 ///   local instance.
 /// - The  _outbound_ proxy receives traffic from the local instance and forwards it to a
 ///   remote service.
+///
+/// This type is used for the purposes of caching and telemetry.
 #[derive(Clone, Copy, Debug, Hash, PartialEq, Eq)]
 pub enum Proxy {
     Inbound,

src/telemetry/metrics/labels.rs

@@ -12,9 +12,7 @@ use transport::tls;
 
 #[derive(Clone, Debug, Eq, PartialEq, Hash)]
 pub struct RequestLabels {
-
-    /// Was the request in the inbound or outbound direction?
-    direction: Direction,
+    proxy: ctx::Proxy,
 
     // Additional labels identifying the destination service of an outbound
     // request, provided by service discovery.
@@ -50,9 +48,6 @@ pub enum Classification {
     Failure,
 }
 
-#[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
-pub struct Direction(ctx::Proxy);
-
 #[derive(Clone, Debug, Eq, PartialEq, Hash)]
 struct DstLabels(String);
 
@@ -72,8 +67,6 @@ struct GrpcStatus(u32);
 
 impl RequestLabels {
     pub fn new(req: &ctx::http::Request) -> Self {
-        let direction = Direction::new(req.server.proxy);
-
         let outbound_labels = DstLabels::new(req.labels());
 
         let authority = req.uri
@@ -81,7 +74,7 @@ impl RequestLabels {
             .cloned();
 
         RequestLabels {
-            direction,
+            proxy: req.server.proxy,
             outbound_labels,
             authority: Authority(authority),
             tls_status: TlsStatus(req.tls_status()),
@@ -98,7 +91,7 @@ impl FmtLabels for RequestLabels {
     fn fmt_labels(&self, f: &mut fmt::Formatter) -> fmt::Result {
         let dst = (self.outbound_labels.as_ref(), &self.tls_status);
 
-        ((&self.authority, &self.direction), dst).fmt_labels(f)
+        ((&self.authority, &self.proxy), dst).fmt_labels(f)
     }
 }
 
@@ -203,17 +196,10 @@ impl FmtLabels for Classification {
     }
 }
 
-// ===== impl Direction =====
-
-impl Direction {
-    pub fn new(ctx: ctx::Proxy) -> Self {
-        Direction(ctx)
-    }
-}
-
-impl FmtLabels for Direction {
+// TODO https://github.com/linkerd/linkerd2/issues/1486
+impl FmtLabels for ctx::Proxy {
     fn fmt_labels(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match self.0 {
+        match *self {
             ctx::Proxy::Inbound => f.pad("direction=\"inbound\""),
             ctx::Proxy::Outbound => f.pad("direction=\"outbound\""),
         }

src/telemetry/metrics/transport.rs

@@ -4,7 +4,7 @@ use std::time::Duration;
 
 use ctx;
 use super::{
-    labels::{Direction, TlsStatus},
+    labels::TlsStatus,
     latency,
     prom::{FmtLabels, FmtMetrics},
     Counter,
@@ -36,7 +36,7 @@ pub struct Transports {
 /// Implements `fmt::Display` to render a comma-separated list of key-value pairs.
 #[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
 struct Key {
-    direction: Direction,
+    proxy: ctx::Proxy,
     peer: Peer,
     tls_status: TlsStatus,
 }
@@ -181,14 +181,14 @@ impl FmtMetrics for Transports {
 
 impl FmtLabels for Key {
     fn fmt_labels(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        ((self.direction, self.peer), self.tls_status).fmt_labels(f)
+        ((self.proxy, self.peer), self.tls_status).fmt_labels(f)
     }
 }
 
 impl Key {
     fn new(ctx: &ctx::transport::Ctx) -> Self {
         Self {
-            direction: Direction::new(ctx.proxy()),
+            proxy: ctx.proxy(),
             peer: match *ctx {
                 ctx::transport::Ctx::Server(_) => Peer::Src,
                 ctx::transport::Ctx::Client(_) => Peer::Dst,