feat(http/retry): model ReplayBody<B> with Frame<T>
#3598
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olix0r
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Feb 6, 2025
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February 6, 2025 15:50
some tests do not set up a tracing subscriber, because they do not use the shared `Test::new()` helper function used elsewhere in this test suite. to provide a trace of the test's execution in the event of a failure, initialize a tracing subscriber in some additional unit tests. Signed-off-by: katelyn martin <kate@buoyant.io>
this commit removes the `cfg(test)` gate on the method exposing `B::is_end_stream()`, and introduces another method also exposing the `size_hint()` method. we will want these in order to implement these methods for `ReplayBody<B>`. Signed-off-by: katelyn martin <kate@buoyant.io>
in the same manner as the existing `frame()` method mimics `http_body_util::BodyExt::frame()`, this commit introduces a new `ForwardCompatibleBody::poll_frame()` method. this allows us to poll the compatibility layer for a `Frame<T>`. Signed-off-by: katelyn martin <kate@buoyant.io>
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>
this commit introduces some trace-level diagnostics tracking how the replay body has determined whether or not it has reached the end of the stream. Signed-off-by: katelyn martin <kate@buoyant.io>
Signed-off-by: katelyn martin <kate@buoyant.io>
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pr #3559 (dd4fbcd) refactored our trailer peeking body middleware to
model its buffering in terms of the
Frame<T>type used inhttp-body's 1.0 release.this branch performs a similar change for the other piece of body
middleware that super linkerd's retry facilities:
ReplayBody<B>. theinner body
Bis now wrapped in theForwardCompatibleBody<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
Bodythat includespoll_trailers().see the comment above
replay_trailersfor more on this, describing whywe now initialize this to
true. relatedly, this is why we no longerdelegate down to
B::poll_trailersourselves. it will have already beencalled by our adapter.
ReplayBody::is_end_stream()now behaves identically when initiallypolling 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.
in the same manner as the existing
frame()method mimicshttp_body_util::BodyExt::frame(), this branch introducesa new
ForwardCompatibleBody::poll_frame()method.this allows us to poll the compatibility layer for a
Frame<T>.see:
PeekTrailersBody<B>withFrame<T>#3559