chore: Reduce how much code gets monomorphized (#1032)

tonic/src/client/grpc.rs

@@ -2,7 +2,7 @@ use crate::codec::compression::{CompressionEncoding, EnabledCompressionEncodings
 use crate::{
     body::BoxBody,
     client::GrpcService,
-    codec::{encode_client, Codec, Streaming},
+    codec::{encode_client, Codec, Decoder, Streaming},
     request::SanitizeHeaders,
     Code, Request, Response, Status,
 };
@@ -30,6 +30,10 @@ use std::fmt;
 /// [gRPC protocol definition]: https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests
 pub struct Grpc<T> {
     inner: T,
+    config: GrpcConfig,
+}
+
+struct GrpcConfig {
     origin: Uri,
     /// Which compression encodings does the client accept?
     accept_compression_encodings: EnabledCompressionEncodings,
@@ -40,12 +44,7 @@ pub struct Grpc<T> {
 impl<T> Grpc<T> {
     /// Creates a new gRPC client with the provided [`GrpcService`].
     pub fn new(inner: T) -> Self {
-        Self {
+        Self::with_origin(inner, Uri::default())
-            inner,
-            origin: Uri::default(),
-            send_compression_encodings: None,
-            accept_compression_encodings: EnabledCompressionEncodings::default(),
-        }
     }
 
     /// Creates a new gRPC client with the provided [`GrpcService`] and `Uri`.
@@ -55,9 +54,11 @@ impl<T> Grpc<T> {
     pub fn with_origin(inner: T, origin: Uri) -> Self {
         Self {
             inner,
-            origin,
+            config: GrpcConfig {
-            send_compression_encodings: None,
+                origin,
-            accept_compression_encodings: EnabledCompressionEncodings::default(),
+                send_compression_encodings: None,
+                accept_compression_encodings: EnabledCompressionEncodings::default(),
+            },
         }
     }
 
@@ -88,7 +89,7 @@ impl<T> Grpc<T> {
     /// # };
     /// ```
     pub fn send_compressed(mut self, encoding: CompressionEncoding) -> Self {
-        self.send_compression_encodings = Some(encoding);
+        self.config.send_compression_encodings = Some(encoding);
         self
     }
 
@@ -119,7 +120,7 @@ impl<T> Grpc<T> {
     /// # };
     /// ```
     pub fn accept_compressed(mut self, encoding: CompressionEncoding) -> Self {
-        self.accept_compression_encodings.enable(encoding);
+        self.config.accept_compression_encodings.enable(encoding);
         self
     }
 
@@ -226,6 +227,73 @@ impl<T> Grpc<T> {
         M1: Send + Sync + 'static,
         M2: Send + Sync + 'static,
     {
+        let request = request
+            .map(|s| encode_client(codec.encoder(), s, self.config.send_compression_encodings))
+            .map(BoxBody::new);
+
+        let request = self.config.prepare_request(request, path);
+
+        let response = self
+            .inner
+            .call(request)
+            .await
+            .map_err(Status::from_error_generic)?;
+
+        let decoder = codec.decoder();
+
+        self.create_response(decoder, response)
+    }
+
+    // Keeping this code in a separate function from Self::streaming lets functions that return the
+    // same output share the generated binary code
+    fn create_response<M2>(
+        &self,
+        decoder: impl Decoder<Item = M2, Error = Status> + Send + 'static,
+        response: http::Response<T::ResponseBody>,
+    ) -> Result<Response<Streaming<M2>>, Status>
+    where
+        T: GrpcService<BoxBody>,
+        T::ResponseBody: Body + Send + 'static,
+        <T::ResponseBody as Body>::Error: Into<crate::Error>,
+    {
+        let encoding = CompressionEncoding::from_encoding_header(
+            response.headers(),
+            self.config.accept_compression_encodings,
+        )?;
+
+        let status_code = response.status();
+        let trailers_only_status = Status::from_header_map(response.headers());
+
+        // We do not need to check for trailers if the `grpc-status` header is present
+        // with a valid code.
+        let expect_additional_trailers = if let Some(status) = trailers_only_status {
+            if status.code() != Code::Ok {
+                return Err(status);
+            }
+
+            false
+        } else {
+            true
+        };
+
+        let response = response.map(|body| {
+            if expect_additional_trailers {
+                Streaming::new_response(decoder, body, status_code, encoding)
+            } else {
+                Streaming::new_empty(decoder, body)
+            }
+        });
+
+        Ok(Response::from_http(response))
+    }
+}
+
+impl GrpcConfig {
+    fn prepare_request(
+        &self,
+        request: Request<http_body::combinators::UnsyncBoxBody<bytes::Bytes, Status>>,
+        path: PathAndQuery,
+    ) -> http::Request<http_body::combinators::UnsyncBoxBody<bytes::Bytes, Status>> {
         let scheme = self.origin.scheme().cloned();
         let authority = self.origin.authority().cloned();
 
@@ -236,10 +304,6 @@ impl<T> Grpc<T> {
 
         let uri = Uri::from_parts(parts).expect("path_and_query only is valid Uri");
 
-        let request = request
-            .map(|s| encode_client(codec.encoder(), s, self.send_compression_encodings))
-            .map(BoxBody::new);
-
         let mut request = request.into_http(
             uri,
             http::Method::POST,
@@ -274,41 +338,7 @@ impl<T> Grpc<T> {
             );
         }
 
-        let response = self
+        request
-            .inner
-            .call(request)
-            .await
-            .map_err(|err| Status::from_error(err.into()))?;
-
-        let encoding = CompressionEncoding::from_encoding_header(
-            response.headers(),
-            self.accept_compression_encodings,
-        )?;
-
-        let status_code = response.status();
-        let trailers_only_status = Status::from_header_map(response.headers());
-
-        // We do not need to check for trailers if the `grpc-status` header is present
-        // with a valid code.
-        let expect_additional_trailers = if let Some(status) = trailers_only_status {
-            if status.code() != Code::Ok {
-                return Err(status);
-            }
-
-            false
-        } else {
-            true
-        };
-
-        let response = response.map(|body| {
-            if expect_additional_trailers {
-                Streaming::new_response(codec.decoder(), body, status_code, encoding)
-            } else {
-                Streaming::new_empty(codec.decoder(), body)
-            }
-        });
-
-        Ok(Response::from_http(response))
     }
 }
 
@@ -316,9 +346,11 @@ impl<T: Clone> Clone for Grpc<T> {
     fn clone(&self) -> Self {
         Self {
             inner: self.inner.clone(),
-            origin: self.origin.clone(),
+            config: GrpcConfig {
-            send_compression_encodings: self.send_compression_encodings,
+                origin: self.config.origin.clone(),
-            accept_compression_encodings: self.accept_compression_encodings,
+                send_compression_encodings: self.config.send_compression_encodings,
+                accept_compression_encodings: self.config.accept_compression_encodings,
+            },
         }
     }
 }
@@ -329,13 +361,16 @@ impl<T: fmt::Debug> fmt::Debug for Grpc<T> {
 
         f.field("inner", &self.inner);
 
-        f.field("origin", &self.origin);
+        f.field("origin", &self.config.origin);
 
-        f.field("compression_encoding", &self.send_compression_encodings);
+        f.field(
+            "compression_encoding",
+            &self.config.send_compression_encodings,
+        );
 
         f.field(
             "accept_compression_encodings",
-            &self.accept_compression_encodings,
+            &self.config.accept_compression_encodings,
         );
 
         f.finish()

tonic/src/codec/decode.rs

@@ -21,6 +21,10 @@ const BUFFER_SIZE: usize = 8 * 1024;
 /// to fetch the message stream and trailing metadata
 pub struct Streaming<T> {
     decoder: Box<dyn Decoder<Item = T, Error = Status> + Send + 'static>,
+    inner: StreamingInner,
+}
+
+struct StreamingInner {
     body: BoxBody,
     state: State,
     direction: Direction,
@@ -96,20 +100,157 @@ impl<T> Streaming<T> {
     {
         Self {
             decoder: Box::new(decoder),
-            body: body
+            inner: StreamingInner {
-                .map_data(|mut buf| buf.copy_to_bytes(buf.remaining()))
+                body: body
-                .map_err(|err| Status::map_error(err.into()))
+                    .map_data(|mut buf| buf.copy_to_bytes(buf.remaining()))
-                .boxed_unsync(),
+                    .map_err(|err| Status::map_error(err.into()))
-            state: State::ReadHeader,
+                    .boxed_unsync(),
-            direction,
+                state: State::ReadHeader,
-            buf: BytesMut::with_capacity(BUFFER_SIZE),
+                direction,
-            trailers: None,
+                buf: BytesMut::with_capacity(BUFFER_SIZE),
-            decompress_buf: BytesMut::new(),
+                trailers: None,
-            encoding,
+                decompress_buf: BytesMut::new(),
+                encoding,
+            },
         }
     }
 }
 
+impl StreamingInner {
+    fn decode_chunk(&mut self) -> Result<Option<DecodeBuf<'_>>, Status> {
+        if let State::ReadHeader = self.state {
+            if self.buf.remaining() < HEADER_SIZE {
+                return Ok(None);
+            }
+
+            let compression_encoding = match self.buf.get_u8() {
+                0 => None,
+                1 => {
+                    {
+                        if self.encoding.is_some() {
+                            self.encoding
+                        } else {
+                            // https://grpc.github.io/grpc/core/md_doc_compression.html
+                            // An ill-constructed message with its Compressed-Flag bit set but lacking a grpc-encoding
+                            // entry different from identity in its metadata MUST fail with INTERNAL status,
+                            // its associated description indicating the invalid Compressed-Flag condition.
+                            return Err(Status::new(Code::Internal, "protocol error: received message with compressed-flag but no grpc-encoding was specified"));
+                        }
+                    }
+                }
+                f => {
+                    trace!("unexpected compression flag");
+                    let message = if let Direction::Response(status) = self.direction {
+                        format!(
+                            "protocol error: received message with invalid compression flag: {} (valid flags are 0 and 1) while receiving response with status: {}",
+                            f, status
+                        )
+                    } else {
+                        format!("protocol error: received message with invalid compression flag: {} (valid flags are 0 and 1), while sending request", f)
+                    };
+                    return Err(Status::new(Code::Internal, message));
+                }
+            };
+            let len = self.buf.get_u32() as usize;
+            self.buf.reserve(len);
+
+            self.state = State::ReadBody {
+                compression: compression_encoding,
+                len,
+            }
+        }
+
+        if let State::ReadBody { len, compression } = self.state {
+            // if we haven't read enough of the message then return and keep
+            // reading
+            if self.buf.remaining() < len || self.buf.len() < len {
+                return Ok(None);
+            }
+
+            let decode_buf = if let Some(encoding) = compression {
+                self.decompress_buf.clear();
+
+                if let Err(err) = decompress(encoding, &mut self.buf, &mut self.decompress_buf, len)
+                {
+                    let message = if let Direction::Response(status) = self.direction {
+                        format!(
+                            "Error decompressing: {}, while receiving response with status: {}",
+                            err, status
+                        )
+                    } else {
+                        format!("Error decompressing: {}, while sending request", err)
+                    };
+                    return Err(Status::new(Code::Internal, message));
+                }
+                let decompressed_len = self.decompress_buf.len();
+                DecodeBuf::new(&mut self.decompress_buf, decompressed_len)
+            } else {
+                DecodeBuf::new(&mut self.buf, len)
+            };
+
+            return Ok(Some(decode_buf));
+        }
+
+        Ok(None)
+    }
+
+    // Returns Some(()) if data was found or None if the loop in `poll_next` should break
+    fn poll_data(&mut self, cx: &mut Context<'_>) -> Poll<Result<Option<()>, Status>> {
+        let chunk = match ready!(Pin::new(&mut self.body).poll_data(cx)) {
+            Some(Ok(d)) => Some(d),
+            Some(Err(e)) => {
+                let _ = std::mem::replace(&mut self.state, State::Error);
+                let err: crate::Error = e.into();
+                debug!("decoder inner stream error: {:?}", err);
+                let status = Status::from_error(err);
+                return Poll::Ready(Err(status));
+            }
+            None => None,
+        };
+
+        Poll::Ready(if let Some(data) = chunk {
+            self.buf.put(data);
+            Ok(Some(()))
+        } else {
+            // FIXME: improve buf usage.
+            if self.buf.has_remaining() {
+                trace!("unexpected EOF decoding stream");
+                Err(Status::new(
+                    Code::Internal,
+                    "Unexpected EOF decoding stream.".to_string(),
+                ))
+            } else {
+                Ok(None)
+            }
+        })
+    }
+
+    fn poll_response(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Status>> {
+        if let Direction::Response(status) = self.direction {
+            match ready!(Pin::new(&mut self.body).poll_trailers(cx)) {
+                Ok(trailer) => {
+                    if let Err(e) = crate::status::infer_grpc_status(trailer.as_ref(), status) {
+                        if let Some(e) = e {
+                            return Poll::Ready(Err(e));
+                        } else {
+                            return Poll::Ready(Ok(()));
+                        }
+                    } else {
+                        self.trailers = trailer.map(MetadataMap::from_headers);
+                    }
+                }
+                Err(e) => {
+                    let err: crate::Error = e.into();
+                    debug!("decoder inner trailers error: {:?}", err);
+                    let status = Status::from_error(err);
+                    return Poll::Ready(Err(status));
+                }
+            }
+        }
+        Poll::Ready(Ok(()))
+    }
+}
+
 impl<T> Streaming<T> {
     /// Fetch the next message from this stream.
     ///
@@ -165,7 +306,7 @@ impl<T> Streaming<T> {
     pub async fn trailers(&mut self) -> Result<Option<MetadataMap>, Status> {
         // Shortcut to see if we already pulled the trailers in the stream step
         // we need to do that so that the stream can error on trailing grpc-status
-        if let Some(trailers) = self.trailers.take() {
+        if let Some(trailers) = self.inner.trailers.take() {
             return Ok(Some(trailers));
         }
 
@@ -174,13 +315,13 @@ impl<T> Streaming<T> {
 
         // Since we call poll_trailers internally on poll_next we need to
         // check if it got cached again.
-        if let Some(trailers) = self.trailers.take() {
+        if let Some(trailers) = self.inner.trailers.take() {
             return Ok(Some(trailers));
         }
 
         // Trailers were not caught during poll_next and thus lets poll for
         // them manually.
-        let map = future::poll_fn(|cx| Pin::new(&mut self.body).poll_trailers(cx))
+        let map = future::poll_fn(|cx| Pin::new(&mut self.inner.body).poll_trailers(cx))
             .await
             .map_err(|e| Status::from_error(Box::new(e)));
 
@@ -188,90 +329,16 @@ impl<T> Streaming<T> {
     }
 
     fn decode_chunk(&mut self) -> Result<Option<T>, Status> {
-        if let State::ReadHeader = self.state {
+        match self.inner.decode_chunk()? {
-            if self.buf.remaining() < HEADER_SIZE {
+            Some(mut decode_buf) => match self.decoder.decode(&mut decode_buf)? {
-                return Ok(None);
+                Some(msg) => {
-            }
+                    self.inner.state = State::ReadHeader;
-
-            let compression_encoding = match self.buf.get_u8() {
-                0 => None,
-                1 => {
-                    {
-                        if self.encoding.is_some() {
-                            self.encoding
-                        } else {
-                            // https://grpc.github.io/grpc/core/md_doc_compression.html
-                            // An ill-constructed message with its Compressed-Flag bit set but lacking a grpc-encoding
-                            // entry different from identity in its metadata MUST fail with INTERNAL status,
-                            // its associated description indicating the invalid Compressed-Flag condition.
-                            return Err(Status::new(Code::Internal, "protocol error: received message with compressed-flag but no grpc-encoding was specified"));
-                        }
-                    }
-                }
-                f => {
-                    trace!("unexpected compression flag");
-                    let message = if let Direction::Response(status) = self.direction {
-                        format!(
-                            "protocol error: received message with invalid compression flag: {} (valid flags are 0 and 1) while receiving response with status: {}",
-                            f, status
-                        )
-                    } else {
-                        format!("protocol error: received message with invalid compression flag: {} (valid flags are 0 and 1), while sending request", f)
-                    };
-                    return Err(Status::new(Code::Internal, message));
-                }
-            };
-            let len = self.buf.get_u32() as usize;
-            self.buf.reserve(len);
-
-            self.state = State::ReadBody {
-                compression: compression_encoding,
-                len,
-            }
-        }
-
-        if let State::ReadBody { len, compression } = self.state {
-            // if we haven't read enough of the message then return and keep
-            // reading
-            if self.buf.remaining() < len || self.buf.len() < len {
-                return Ok(None);
-            }
-
-            let decoding_result = if let Some(encoding) = compression {
-                self.decompress_buf.clear();
-
-                if let Err(err) = decompress(encoding, &mut self.buf, &mut self.decompress_buf, len)
-                {
-                    let message = if let Direction::Response(status) = self.direction {
-                        format!(
-                            "Error decompressing: {}, while receiving response with status: {}",
-                            err, status
-                        )
-                    } else {
-                        format!("Error decompressing: {}, while sending request", err)
-                    };
-                    return Err(Status::new(Code::Internal, message));
-                }
-                let decompressed_len = self.decompress_buf.len();
-                self.decoder.decode(&mut DecodeBuf::new(
-                    &mut self.decompress_buf,
-                    decompressed_len,
-                ))
-            } else {
-                self.decoder.decode(&mut DecodeBuf::new(&mut self.buf, len))
-            };
-
-            return match decoding_result {
-                Ok(Some(msg)) => {
-                    self.state = State::ReadHeader;
                     Ok(Some(msg))
                 }
-                Ok(None) => Ok(None),
+                None => Ok(None),
-                Err(e) => Err(e),
+            },
-            };
+            None => Ok(None),
         }
-
-        Ok(None)
     }
 }
 
@@ -280,7 +347,7 @@ impl<T> Stream for Streaming<T> {
 
     fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
         loop {
-            if let State::Error = &self.state {
+            if let State::Error = &self.inner.state {
                 return Poll::Ready(None);
             }
 
@@ -291,57 +358,16 @@ impl<T> Stream for Streaming<T> {
                 return Poll::Ready(Some(Ok(item)));
             }
 
-            let chunk = match ready!(Pin::new(&mut self.body).poll_data(cx)) {
+            match ready!(self.inner.poll_data(cx))? {
-                Some(Ok(d)) => Some(d),
+                Some(()) => (),
-                Some(Err(e)) => {
+                None => break,
-                    let _ = std::mem::replace(&mut self.state, State::Error);
-                    let err: crate::Error = e.into();
-                    debug!("decoder inner stream error: {:?}", err);
-                    let status = Status::from_error(err);
-                    return Poll::Ready(Some(Err(status)));
-                }
-                None => None,
-            };
-
-            if let Some(data) = chunk {
-                self.buf.put(data);
-            } else {
-                // FIXME: improve buf usage.
-                if self.buf.has_remaining() {
-                    trace!("unexpected EOF decoding stream");
-                    return Poll::Ready(Some(Err(Status::new(
-                        Code::Internal,
-                        "Unexpected EOF decoding stream.".to_string(),
-                    ))));
-                } else {
-                    break;
-                }
             }
         }
 
-        if let Direction::Response(status) = self.direction {
+        Poll::Ready(match ready!(self.inner.poll_response(cx)) {
-            match ready!(Pin::new(&mut self.body).poll_trailers(cx)) {
+            Ok(()) => None,
-                Ok(trailer) => {
+            Err(err) => Some(Err(err)),
-                    if let Err(e) = crate::status::infer_grpc_status(trailer.as_ref(), status) {
+        })
-                        if let Some(e) = e {
-                            return Some(Err(e)).into();
-                        } else {
-                            return Poll::Ready(None);
-                        }
-                    } else {
-                        self.trailers = trailer.map(MetadataMap::from_headers);
-                    }
-                }
-                Err(e) => {
-                    let err: crate::Error = e.into();
-                    debug!("decoder inner trailers error: {:?}", err);
-                    let status = Status::from_error(err);
-                    return Some(Err(status)).into();
-                }
-            }
-        }
-
-        Poll::Ready(None)
     }
 }
 

tonic/src/codec/encode.rs

@@ -58,66 +58,80 @@ where
     T: Encoder<Error = Status>,
     U: Stream<Item = Result<T::Item, Status>>,
 {
-    async_stream::stream! {
+    let mut buf = BytesMut::with_capacity(BUFFER_SIZE);
-        let mut buf = BytesMut::with_capacity(BUFFER_SIZE);
 
-        let compression_encoding = if compression_override == SingleMessageCompressionOverride::Disable {
+    let compression_encoding = if compression_override == SingleMessageCompressionOverride::Disable
-            None
+    {
-        } else {
+        None
-            compression_encoding
+    } else {
-        };
+        compression_encoding
+    };
 
-        let mut uncompression_buf = if compression_encoding.is_some() {
+    let mut uncompression_buf = if compression_encoding.is_some() {
-            BytesMut::with_capacity(BUFFER_SIZE)
+        BytesMut::with_capacity(BUFFER_SIZE)
-        } else {
+    } else {
-            BytesMut::new()
+        BytesMut::new()
-        };
+    };
 
-        futures_util::pin_mut!(source);
+    source.map(move |result| {
+        let item = result?;
 
-        loop {
+        encode_item(
-            match source.next().await {
+            &mut encoder,
-                Some(Ok(item)) => {
+            &mut buf,
-                    buf.reserve(HEADER_SIZE);
+            &mut uncompression_buf,
-                    unsafe {
+            compression_encoding,
-                        buf.advance_mut(HEADER_SIZE);
+            item,
-                    }
+        )
+    })
+}
 
-                    if let Some(encoding) = compression_encoding {
+fn encode_item<T>(
-                        uncompression_buf.clear();
+    encoder: &mut T,
-
+    buf: &mut BytesMut,
-                        encoder.encode(item, &mut EncodeBuf::new(&mut uncompression_buf))
+    uncompression_buf: &mut BytesMut,
-                            .map_err(|err| Status::internal(format!("Error encoding: {}", err)))?;
+    compression_encoding: Option<CompressionEncoding>,
-
+    item: T::Item,
-                        let uncompressed_len = uncompression_buf.len();
+) -> Result<Bytes, Status>
-
+where
-                        compress(
+    T: Encoder<Error = Status>,
-                            encoding,
+{
-                            &mut uncompression_buf,
+    buf.reserve(HEADER_SIZE);
-                            &mut buf,
+    unsafe {
-                            uncompressed_len,
+        buf.advance_mut(HEADER_SIZE);
-                        ).map_err(|err| Status::internal(format!("Error compressing: {}", err)))?;
-                    } else {
-                        encoder.encode(item, &mut EncodeBuf::new(&mut buf))
-                            .map_err(|err| Status::internal(format!("Error encoding: {}", err)))?;
-                    }
-
-                    // now that we know length, we can write the header
-                    let len = buf.len() - HEADER_SIZE;
-                    assert!(len <= std::u32::MAX as usize);
-                    {
-                        let mut buf = &mut buf[..HEADER_SIZE];
-                        buf.put_u8(compression_encoding.is_some() as u8);
-                        buf.put_u32(len as u32);
-                    }
-
-                    yield Ok(buf.split_to(len + HEADER_SIZE).freeze());
-                },
-                Some(Err(status)) => yield Err(status),
-                None => break,
-            }
-        }
     }
+
+    if let Some(encoding) = compression_encoding {
+        uncompression_buf.clear();
+
+        encoder
+            .encode(item, &mut EncodeBuf::new(uncompression_buf))
+            .map_err(|err| Status::internal(format!("Error encoding: {}", err)))?;
+
+        let uncompressed_len = uncompression_buf.len();
+
+        compress(encoding, uncompression_buf, buf, uncompressed_len)
+            .map_err(|err| Status::internal(format!("Error compressing: {}", err)))?;
+    } else {
+        encoder
+            .encode(item, &mut EncodeBuf::new(buf))
+            .map_err(|err| Status::internal(format!("Error encoding: {}", err)))?;
+    }
+
+    // now that we know length, we can write the header
+    Ok(finish_encoding(compression_encoding, buf))
+}
+
+fn finish_encoding(compression_encoding: Option<CompressionEncoding>, buf: &mut BytesMut) -> Bytes {
+    let len = buf.len() - HEADER_SIZE;
+    assert!(len <= std::u32::MAX as usize);
+    {
+        let mut buf = &mut buf[..HEADER_SIZE];
+        buf.put_u8(compression_encoding.is_some() as u8);
+        buf.put_u32(len as u32);
+    }
+
+    buf.split_to(len + HEADER_SIZE).freeze()
 }
 
 #[derive(Debug)]
@@ -131,6 +145,11 @@ enum Role {
 pub(crate) struct EncodeBody<S> {
     #[pin]
     inner: S,
+    state: EncodeState,
+}
+
+#[derive(Debug)]
+struct EncodeState {
     error: Option<Status>,
     role: Role,
     is_end_stream: bool,
@@ -143,18 +162,44 @@ where
     pub(crate) fn new_client(inner: S) -> Self {
         Self {
             inner,
-            error: None,
+            state: EncodeState {
-            role: Role::Client,
+                error: None,
-            is_end_stream: false,
+                role: Role::Client,
+                is_end_stream: false,
+            },
         }
     }
 
     pub(crate) fn new_server(inner: S) -> Self {
         Self {
             inner,
-            error: None,
+            state: EncodeState {
-            role: Role::Server,
+                error: None,
-            is_end_stream: false,
+                role: Role::Server,
+                is_end_stream: false,
+            },
+        }
+    }
+}
+
+impl EncodeState {
+    fn trailers(&mut self) -> Result<Option<HeaderMap>, Status> {
+        match self.role {
+            Role::Client => Ok(None),
+            Role::Server => {
+                if self.is_end_stream {
+                    return Ok(None);
+                }
+
+                let status = if let Some(status) = self.error.take() {
+                    self.is_end_stream = true;
+                    status
+                } else {
+                    Status::new(Code::Ok, "")
+                };
+
+                Ok(Some(status.to_header_map()?))
+            }
         }
     }
 }
@@ -167,7 +212,7 @@ where
     type Error = Status;
 
     fn is_end_stream(&self) -> bool {
-        self.is_end_stream
+        self.state.is_end_stream
     }
 
     fn poll_data(
@@ -177,10 +222,10 @@ where
         let mut self_proj = self.project();
         match ready!(self_proj.inner.try_poll_next_unpin(cx)) {
             Some(Ok(d)) => Some(Ok(d)).into(),
-            Some(Err(status)) => match self_proj.role {
+            Some(Err(status)) => match self_proj.state.role {
                 Role::Client => Some(Err(status)).into(),
                 Role::Server => {
-                    *self_proj.error = Some(status);
+                    self_proj.state.error = Some(status);
                     None.into()
                 }
             },
@@ -192,24 +237,6 @@ where
         self: Pin<&mut Self>,
         _cx: &mut Context<'_>,
     ) -> Poll<Result<Option<HeaderMap>, Status>> {
-        match self.role {
+        Poll::Ready(self.project().state.trailers())
-            Role::Client => Poll::Ready(Ok(None)),
-            Role::Server => {
-                let self_proj = self.project();
-
-                if *self_proj.is_end_stream {
-                    return Poll::Ready(Ok(None));
-                }
-
-                let status = if let Some(status) = self_proj.error.take() {
-                    *self_proj.is_end_stream = true;
-                    status
-                } else {
-                    Status::new(Code::Ok, "")
-                };
-
-                Poll::Ready(Ok(Some(status.to_header_map()?)))
-            }
-        }
     }
 }

tonic/src/status.rs

@@ -303,6 +303,13 @@ impl Status {
         Status::new(Code::Unauthenticated, message)
     }
 
+    #[cfg_attr(not(feature = "transport"), allow(dead_code))]
+    pub(crate) fn from_error_generic(
+        err: impl Into<Box<dyn Error + Send + Sync + 'static>>,
+    ) -> Status {
+        Self::from_error(err.into())
+    }
+
     #[cfg_attr(not(feature = "transport"), allow(dead_code))]
     pub(crate) fn from_error(err: Box<dyn Error + Send + Sync + 'static>) -> Status {
         Status::try_from_error(err).unwrap_or_else(|err| {

tonic/src/transport/server/incoming.rs

@@ -23,13 +23,7 @@ where
     IO: AsyncRead + AsyncWrite + Connected + Unpin + Send + 'static,
     IE: Into<crate::Error>,
 {
-    async_stream::try_stream! {
+    incoming.err_into().map_ok(ServerIo::new_io)
-        futures_util::pin_mut!(incoming);
-
-        while let Some(stream) = incoming.try_next().await? {
-            yield ServerIo::new_io(stream);
-        }
-    }
 }
 
 #[cfg(feature = "tls")]