refactor(http/retry): outline ForwardCompatibleBody<B>

in #3559 (4b53081), we introduced a backported `Frame<T>` type, and a
`ForwardCompatibleBody<B>` type that allows us to interact with a
`http_body::Body` circa 0.4.6 in terms of frame-based interfaces that
match those of the 1.0 interface.

see linkerd/linkerd2#8733 for more information on upgrading hyper.

in #3559, we narrowly added this as an internal submodule of the
`linkerd-http-retry` library. these facilities however, would have
utility in other places such as `linkerd-app-core`.

this commit pulls these compatibility shims out into a
`linkerd-http-body-compat` library so that they can be imported and
reused elsewhere.

Signed-off-by: katelyn martin <[email protected]>

Cargo.lock

@@ -1687,6 +1687,14 @@ dependencies = [
  "tracing",
 ]
 
+[[package]]
+name = "linkerd-http-body-compat"
+version = "0.1.0"
+dependencies = [
+ "http",
+ "http-body",
+]
+
 [[package]]
 name = "linkerd-http-box"
 version = "0.1.0"
@@ -1813,6 +1821,7 @@ dependencies = [
  "hyper",
  "linkerd-error",
  "linkerd-exp-backoff",
+ "linkerd-http-body-compat",
  "linkerd-http-box",
  "linkerd-metrics",
  "linkerd-mock-http-body",

Cargo.toml

@@ -25,6 +25,7 @@ members = [
     "linkerd/error-respond",
     "linkerd/exp-backoff",
     "linkerd/http/access-log",
+    "linkerd/http/body-compat",
     "linkerd/http/box",
     "linkerd/http/classify",
     "linkerd/http/executor",

linkerd/http/body-compat/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "linkerd-http-body-compat"
+version = "0.1.0"
+authors = ["Linkerd Developers <[email protected]>"]
+license = "Apache-2.0"
+edition = "2021"
+publish = false
+
+[dependencies]
+http = { workspace = true }
+http-body = { workspace = true }

linkerd/http/retry/src/compat.rs → linkerd/http/body-compat/src/lib.rs

@@ -7,12 +7,12 @@ use std::{
     task::{Context, Poll},
 };
 
-pub(crate) use self::frame::Frame;
+pub use self::frame::Frame;
 
 mod frame;
 
 #[derive(Debug)]
-pub(crate) struct ForwardCompatibleBody<B> {
+pub struct ForwardCompatibleBody<B> {
     inner: B,
     data_finished: bool,
     trailers_finished: bool,
@@ -21,7 +21,7 @@ pub(crate) struct ForwardCompatibleBody<B> {
 // === impl ForwardCompatibleBody ===
 
 impl<B: Body> ForwardCompatibleBody<B> {
-    pub(crate) fn new(body: B) -> Self {
+    pub fn new(body: B) -> Self {
         if body.is_end_stream() {
             Self {
                 inner: body,
@@ -37,28 +37,28 @@ impl<B: Body> ForwardCompatibleBody<B> {
         }
     }
 
-    pub(crate) fn into_inner(self) -> B {
+    pub fn into_inner(self) -> B {
         self.inner
     }
 
     /// Returns a future that resolves to the next frame.
-    pub(crate) fn frame(&mut self) -> combinators::Frame<'_, B> {
+    pub fn frame(&mut self) -> combinators::Frame<'_, B> {
         combinators::Frame(self)
     }
 
     /// Returns `true` when the end of stream has been reached.
-    pub(crate) fn is_end_stream(&self) -> bool {
+    pub fn is_end_stream(&self) -> bool {
         self.inner.is_end_stream()
     }
 
     /// Returns the bounds on the remaining length of the stream.
-    pub(crate) fn size_hint(&self) -> SizeHint {
+    pub fn size_hint(&self) -> SizeHint {
         self.inner.size_hint()
     }
 }
 
 impl<B: Body + Unpin> ForwardCompatibleBody<B> {
-    pub(crate) fn poll_frame(
+    pub fn poll_frame(
         self: Pin<&mut Self>,
         cx: &mut Context<'_>,
     ) -> Poll<Option<Result<Frame<B::Data>, B::Error>>> {

linkerd/http/retry/Cargo.toml

@@ -21,6 +21,7 @@ thiserror = "2"
 linkerd-http-box = { path = "../box" }
 linkerd-error = { path = "../../error" }
 linkerd-exp-backoff = { path = "../../exp-backoff" }
+linkerd-http-body-compat = { path = "../body-compat" }
 linkerd-metrics = { path = "../../metrics" }
 linkerd-stack = { path = "../../stack" }
 

linkerd/http/retry/src/lib.rs

@@ -4,8 +4,6 @@
 pub mod peek_trailers;
 pub mod replay;
 
-mod compat;
-
 pub use self::{peek_trailers::PeekTrailersBody, replay::ReplayBody};
 pub use tower::retry::budget::Budget;
 

linkerd/http/retry/src/peek_trailers.rs

@@ -123,7 +123,7 @@ impl<B: Body> PeekTrailersBody<B> {
     {
         // XXX(kate): for now, wrap this in a compatibility adapter that yields `Frame<T>`s.
         // this can be removed when we upgrade to http-body 1.0.
-        use crate::compat::ForwardCompatibleBody;
+        use linkerd_http_body_compat::ForwardCompatibleBody;
         let mut body = ForwardCompatibleBody::new(body);
 
         // First, poll the body for its first frame.
@@ -220,9 +220,9 @@ impl<B: Body> PeekTrailersBody<B> {
     ///
     /// This is an internal helper to facilitate pattern matching in `read_body(..)`, above.
     fn split_frame(
-        frame: crate::compat::Frame<B::Data>,
+        frame: linkerd_http_body_compat::Frame<B::Data>,
     ) -> Option<futures::future::Either<B::Data, HeaderMap>> {
-        use {crate::compat::Frame, futures::future::Either};
+        use {futures::future::Either, linkerd_http_body_compat::Frame};
         match frame.into_data().map_err(Frame::into_trailers) {
             Ok(data) => Some(Either::Left(data)),
             Err(Ok(trailers)) => Some(Either::Right(trailers)),

linkerd/http/retry/src/replay.rs

@@ -68,7 +68,7 @@ struct SharedState<B> {
 struct BodyState<B> {
     replay: Replay,
     trailers: Option<HeaderMap>,
-    rest: crate::compat::ForwardCompatibleBody<B>,
+    rest: linkerd_http_body_compat::ForwardCompatibleBody<B>,
     is_completed: bool,
 
     /// Maximum number of bytes to buffer.
@@ -104,7 +104,7 @@ impl<B: Body> ReplayBody<B> {
             state: Some(BodyState {
                 replay: Default::default(),
                 trailers: None,
-                rest: crate::compat::ForwardCompatibleBody::new(body),
+                rest: linkerd_http_body_compat::ForwardCompatibleBody::new(body),
                 is_completed: false,
                 max_bytes: max_bytes + 1,
             }),
@@ -368,9 +368,9 @@ impl<B: Body> ReplayBody<B> {
     ///
     /// This is an internal helper to facilitate pattern matching in `read_body(..)`, above.
     fn split_frame(
-        frame: crate::compat::Frame<B::Data>,
+        frame: linkerd_http_body_compat::Frame<B::Data>,
     ) -> Option<futures::future::Either<B::Data, HeaderMap>> {
-        use {crate::compat::Frame, futures::future::Either};
+        use {futures::future::Either, linkerd_http_body_compat::Frame};
         match frame.into_data().map_err(Frame::into_trailers) {
             Ok(data) => Some(Either::Left(data)),
             Err(Ok(trailers)) => Some(Either::Right(trailers)),

linkerd/http/retry/src/replay/tests.rs

@@ -89,7 +89,7 @@ async fn replays_trailers() {
     drop(tx);
 
     let read_trailers = |body: ReplayBody<_>| async move {
-        let mut body = crate::compat::ForwardCompatibleBody::new(body);
+        let mut body = linkerd_http_body_compat::ForwardCompatibleBody::new(body);
         let _ = body
             .frame()
             .await
@@ -126,8 +126,8 @@ async fn replays_trailers_only() {
         replay,
         _trace,
     } = Test::new();
-    let mut initial = crate::compat::ForwardCompatibleBody::new(initial);
-    let mut replay = crate::compat::ForwardCompatibleBody::new(replay);
+    let mut initial = linkerd_http_body_compat::ForwardCompatibleBody::new(initial);
+    let mut replay = linkerd_http_body_compat::ForwardCompatibleBody::new(replay);
 
     let mut tlrs = HeaderMap::new();
     tlrs.insert("x-hello", HeaderValue::from_str("world").unwrap());
@@ -332,8 +332,8 @@ async fn eos_only_when_fully_replayed() {
         .expect("body must not be too large");
     let replay = initial.clone();
 
-    let mut initial = crate::compat::ForwardCompatibleBody::new(initial);
-    let mut replay = crate::compat::ForwardCompatibleBody::new(replay);
+    let mut initial = linkerd_http_body_compat::ForwardCompatibleBody::new(initial);
+    let mut replay = linkerd_http_body_compat::ForwardCompatibleBody::new(replay);
 
     // Read the initial body, show that the replay does not consider itself to have reached the
     // end-of-stream. Then drop the initial body, show that the replay is still not done.
@@ -374,7 +374,7 @@ async fn eos_only_when_fully_replayed() {
     drop(replay);
 
     // Read the second replay body.
-    let mut replay2 = crate::compat::ForwardCompatibleBody::new(replay2);
+    let mut replay2 = linkerd_http_body_compat::ForwardCompatibleBody::new(replay2);
     replay2
         .frame()
         .await
@@ -396,8 +396,8 @@ async fn eos_only_when_fully_replayed_with_trailers() {
         .expect("body must not be too large");
     let replay = initial.clone();
 
-    let mut initial = crate::compat::ForwardCompatibleBody::new(initial);
-    let mut replay = crate::compat::ForwardCompatibleBody::new(replay);
+    let mut initial = linkerd_http_body_compat::ForwardCompatibleBody::new(initial);
+    let mut replay = linkerd_http_body_compat::ForwardCompatibleBody::new(replay);
 
     // Read the initial body, show that the replay does not consider itself to have reached the
     // end-of-stream. Then drop the initial body, show that the replay is still not done.
@@ -450,7 +450,7 @@ async fn eos_only_when_fully_replayed_with_trailers() {
     drop(replay);
 
     // Read the second replay body.
-    let mut replay2 = crate::compat::ForwardCompatibleBody::new(replay2);
+    let mut replay2 = linkerd_http_body_compat::ForwardCompatibleBody::new(replay2);
     replay2
         .frame()
         .await
@@ -508,7 +508,7 @@ async fn caps_buffer() {
 
     // The request's replay should error, since we discarded the buffer when
     // we hit the cap.
-    let mut replay = crate::compat::ForwardCompatibleBody::new(replay);
+    let mut replay = linkerd_http_body_compat::ForwardCompatibleBody::new(replay);
     let err = replay
         .frame()
         .await
@@ -554,7 +554,7 @@ async fn caps_across_replays() {
     drop(replay);
 
     // The second replay will fail, though, because the buffer was discarded.
-    let mut replay2 = crate::compat::ForwardCompatibleBody::new(replay2);
+    let mut replay2 = linkerd_http_body_compat::ForwardCompatibleBody::new(replay2);
     let err = replay2
         .frame()
         .await
@@ -638,7 +638,7 @@ async fn size_hint_is_correct_across_replays() {
     assert_eq!(chunk(&mut initial).await.as_deref(), Some(BODY));
     let initial = {
         // TODO(kate): the initial body doesn't report ending until it has (not) yielded trailers.
-        let mut body = crate::compat::ForwardCompatibleBody::new(initial);
+        let mut body = linkerd_http_body_compat::ForwardCompatibleBody::new(initial);
         assert!(body.frame().await.is_none());
         body.into_inner()
     };
@@ -661,7 +661,7 @@ async fn size_hint_is_correct_across_replays() {
     assert_eq!(chunk(&mut replay).await.as_deref(), Some(BODY));
     // let replay = {
     //     // TODO(kate): the replay doesn't report ending until it has (not) yielded trailers.
-    //     let mut body = crate::compat::ForwardCompatibleBody::new(replay);
+    //     let mut body = linkerd_http_body_compat::ForwardCompatibleBody::new(replay);
     //     assert!(body.frame().await.is_none());
     //     body.into_inner()
     // };
@@ -770,7 +770,7 @@ where
     T: http_body::Body + Unpin,
 {
     tracing::trace!("waiting for a body chunk...");
-    let chunk = crate::compat::ForwardCompatibleBody::new(body)
+    let chunk = linkerd_http_body_compat::ForwardCompatibleBody::new(body)
         .frame()
         .await
         .expect("yields a result")
@@ -788,7 +788,7 @@ where
     B: http_body::Body + Unpin,
     B::Error: std::fmt::Debug,
 {
-    let mut body = crate::compat::ForwardCompatibleBody::new(body);
+    let mut body = linkerd_http_body_compat::ForwardCompatibleBody::new(body);
     let mut data = String::new();
     let mut trailers = None;