refactor(app/core): prepare rescue body for http-body upgrade #3616
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this commit makes some minor alterations to our error recovery body middleware. see linkerd/linkerd2#8733 for more information. this commit removes an `assert!` statement from the implementation of `<Response<R, B> as Body>::poll_data()`. see the documentation of `Body::poll_frame()`: > Once the end of the stream is reached, implementations should > continue to return [`Poll::Ready(None)`]. hyperium/http-body@1090bff#diff-33aabe8c2aaa7614022addf244245e09bbff576a67a9ae3c6938c8a868201d36R60-R61 to do this, this commit introduces a distinct terminal state `Inner::Rescued` to represent when the underlying `B`-typed body has yielded an error and been rescued. once in this state the body will yield no more data frames, instead yielding a collection of trailers describing the mid-stream error that was encountered by the underlying body. the call to `R::rescue` is also moved down into the helper function fka `grpc_trailers()`. this helps the function follow the grain of our "state machine" a little more directly. see #3615, #3614, and #3611 for pretext to this change. Signed-off-by: katelyn martin <[email protected]>
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| } => { | ||
| // should not be calling poll_data if we have set trailers derived from an error | ||
| assert!(trailers.is_none()); | ||
| match inner.poll_data(cx) { | ||
| Poll::Ready(Some(Err(error))) => { | ||
| let SyntheticHttpResponse { | ||
| grpc_status, | ||
| message, | ||
| .. | ||
| } = rescue.rescue(error)?; | ||
| let t = Self::grpc_trailers(grpc_status, &message, *emit_headers); | ||
| *trailers = Some(t); | ||
| Poll::Ready(None) | ||
| } | ||
| data => data, | ||
| } => match inner.poll_data(cx) { | ||
| Poll::Ready(Some(Err(error))) => { | ||
| // The inner body has yielded an error, which we will try to rescue. If so, | ||
| // store our synthetic trailers reporting the error. | ||
| let trailers = Self::rescue(error, rescue, *emit_headers)?; | ||
| self.set_rescued(trailers); | ||
| Poll::Ready(None) |
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this is the important part to look at ☝️
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refactor(app/core): prepare rescue body for http-body upgrade
this commit makes some minor alterations to our error recovery body
middleware. see linkerd/linkerd2#8733 for more
information.
this commit removes an
assert!statement from the implementation of<Response<R, B> as Body>::poll_data(). see the documentation ofBody::poll_frame():hyperium/http-body@1090bff#diff-33aabe8c2aaa7614022addf244245e09bbff576a67a9ae3c6938c8a868201d36R60-R61
to do this, this commit introduces a distinct terminal state
Inner::Rescuedto represent when the underlyingB-typed body hasyielded an error and been rescued. once in this state the body will
yield no more data frames, instead yielding a collection of trailers
describing the mid-stream error that was encountered by the underlying
body.
the call to
R::rescueis also moved down into the helper function fkagrpc_trailers(). this helps the function follow the grain of our"state machine" a little more directly.
see #3615, #3614, and #3611 for pretext to this change.