pr #3559 (dd4fbcd) refactored our trailer peeking body middleware to model its buffering in terms of the `Frame<T>` type used in `http-body`'s 1.0 release. this commit performs a similar change for the other piece of body middleware that super linkerd's retry facilities: `ReplayBody<B>`. the inner body `B` is now wrapped in the `ForwardCompatibleBody<B>` adapter, and we now poll it in terms of frames. NB: polling the underlying in terms of frames has a subtle knock-on effect regarding when we observe the trailers, in the liminal period between this refactor and the subsequent upgrade to hyper 1.0, whilst we must still implement the existing 0.4 interface for `Body` that includes `poll_trailers()`. see the comment above `replay_trailers` for more on this, describing why we now initialize this to `true`. relatedly, this is why we now longer delegate down to `B::poll_trailers` ourselves. it will have already been called by our adapter. `ReplayBody::is_end_stream()` now behaves identically when initially polling a body compared to subsequent replays. this is fine, as `is_end_stream()` is a hint that facilitates optimizations (hyperium/http-body#143). we do still report the end properly, we just won't be quite as prescient on the initial playthrough. see: - linkerd/linkerd2#8733. - #3559 Signed-off-by: katelyn martin <kate@buoyant.io>

Commits

Commits on Feb 6, 2025

nit(http/retry): install tracing subscriber in tests

feat(http/retry): ForwardCompatibleBody<B> exposes hints

refactor(http/retry): ForwardCompatibleBody::poll_frame()

feat(http/retry): ReplayBody<B> polls for frames

feat(http/retry): is_end_stream() traces

nit(http/retry): capitalize trace event messages

feat(http/retry): `ForwardCompatibleBody<B>` exposes hints

refactor(http/retry): `ForwardCompatibleBody::poll_frame()`

feat(http/retry): `ReplayBody<B>` polls for frames

feat(http/retry): `is_end_stream()` traces