Remove the `timestamp_request_open` module (#128)

The `timestamp_request_open` module is no longer used.  It can safely be
removed.

src/app/main.rs

@@ -21,7 +21,7 @@ use metrics::{self, FmtMetrics};
 use never::Never;
 use proxy::{
     self, buffer,
-    http::{client, insert_target, metrics::timestamp_request_open, normalize_uri, router},
+    http::{client, insert_target, normalize_uri, router},
     limit, reconnect, timeout,
 };
 use svc::{self, Layer as _Layer, Stack as _Stack};
@@ -334,7 +334,6 @@ where
                 // including metadata about the request's origin.
                 let server_stack = svc::stack::phantom_data::layer()
                     .push(insert_target::layer())
-                    .push(timestamp_request_open::layer())
                     .bind(svc::shared::stack(router));
 
                 serve(
@@ -404,7 +403,6 @@ where
                 let source_stack = svc::stack::phantom_data::layer()
                     .push(inbound::orig_proto_downgrade::layer())
                     .push(insert_target::layer())
-                    .push(timestamp_request_open::layer())
                     .bind(svc::shared::stack(router));
 
                 serve(
@@ -504,13 +502,6 @@ where
     <B::Data as ::bytes::IntoBuf>::Buf: Send,
     G: GetOriginalDst + Send + 'static,
 {
-    // Install the request open timestamp module at the very top of the
-    // stack, in order to take the timestamp as close as possible to the
-    // beginning of the request's lifetime.
-    //
-    // TODO replace with a metrics module that is registered to the server
-    // transport.
-
     let listen_addr = bound_port.local_addr();
     let server = proxy::Server::new(
         proxy_name,

src/proxy/http/metrics/mod.rs

@@ -10,7 +10,6 @@ use metrics::{latency, Counter, FmtLabels, Histogram};
 pub mod classify;
 mod report;
 mod service;
-pub mod timestamp_request_open;
 
 pub use self::report::Report;
 pub use self::service::layer;

src/proxy/http/metrics/timestamp_request_open.rs

@@ -1,89 +0,0 @@
-use futures::Poll;
-use http;
-use std::time::Instant;
-
-use svc;
-
-/// A `RequestOpen` timestamp.
-///
-/// This is added to a request's `Extensions` by the `TimestampRequestOpen`
-/// middleware. It's a newtype in order to distinguish it from other
-/// `Instant`s that may be added as request extensions.
-#[derive(Copy, Clone, Debug)]
-pub struct RequestOpen(pub Instant);
-
-/// Middleware that adds a `RequestOpen` timestamp to requests.
-///
-/// This is a separate middleware from `sensor::Http`, because we want
-/// to install it at the earliest point in the stack. This is in order
-/// to ensure that request latency metrics cover the overhead added by
-/// the proxy as accurately as possible.
-#[derive(Copy, Clone, Debug)]
-pub struct TimestampRequestOpen<S> {
-    inner: S,
-}
-
-/// Layers a `TimestampRequestOpen` middleware on an HTTP client.
-#[derive(Clone, Debug)]
-pub struct Layer();
-
-/// Uses an `M`-typed `Stack` to build a `TimestampRequestOpen` service.
-#[derive(Clone, Debug)]
-pub struct Stack<M>(M);
-
-// === impl TimestampRequsetOpen ===
-
-impl<S, B> svc::Service for TimestampRequestOpen<S>
-where
-    S: svc::Service<Request = http::Request<B>>,
-{
-    type Request = http::Request<B>;
-    type Response = S::Response;
-    type Error = S::Error;
-    type Future = S::Future;
-
-    fn poll_ready(&mut self) -> Poll<(), Self::Error> {
-        self.inner.poll_ready()
-    }
-
-    fn call(&mut self, mut req: Self::Request) -> Self::Future {
-        req.extensions_mut().insert(RequestOpen(Instant::now()));
-        self.inner.call(req)
-    }
-}
-
-// === impl Layer ===
-
-pub fn layer() -> Layer {
-    Layer()
-}
-
-impl<T, B, M> svc::Layer<T, T, M> for Layer
-where
-    M: svc::Stack<T>,
-    M::Value: svc::Service<Request = http::Request<B>>,
-{
-    type Value = <Stack<M> as svc::Stack<T>>::Value;
-    type Error = <Stack<M> as svc::Stack<T>>::Error;
-    type Stack = Stack<M>;
-
-    fn bind(&self, next: M) -> Self::Stack {
-        Stack(next)
-    }
-}
-
-// === impl Stack ===
-
-impl<T, B, M> svc::Stack<T> for Stack<M>
-where
-    M: svc::Stack<T>,
-    M::Value: svc::Service<Request = http::Request<B>>,
-{
-    type Value = TimestampRequestOpen<M::Value>;
-    type Error = M::Error;
-
-    fn make(&self, target: &T) -> Result<Self::Value, Self::Error> {
-        let inner = self.0.make(target)?;
-        Ok(TimestampRequestOpen { inner })
-    }
-}