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use super::compression::{decompress, CompressionEncoding};
use super::{DecodeBuf, Decoder, DEFAULT_MAX_RECV_MESSAGE_SIZE, HEADER_SIZE};
use crate::{body::BoxBody, metadata::MetadataMap, Code, Status};
use bytes::{Buf, BufMut, BytesMut};
use http::StatusCode;
use http_body::Body;
use std::{
fmt, future,
pin::Pin,
task::ready,
task::{Context, Poll},
};
use tokio_stream::Stream;
use tracing::{debug, trace};
const BUFFER_SIZE: usize = 8 * 1024;
/// Streaming requests and responses.
///
/// This will wrap some inner [`Body`] and [`Decoder`] and provide an interface
/// 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,
buf: BytesMut,
trailers: Option<MetadataMap>,
decompress_buf: BytesMut,
encoding: Option<CompressionEncoding>,
max_message_size: Option<usize>,
}
impl<T> Unpin for Streaming<T> {}
#[derive(Debug, Clone, Copy)]
enum State {
ReadHeader,
ReadBody {
compression: Option<CompressionEncoding>,
len: usize,
},
Error,
}
#[derive(Debug, PartialEq, Eq)]
enum Direction {
Request,
Response(StatusCode),
EmptyResponse,
}
impl<T> Streaming<T> {
pub(crate) fn new_response<B, D>(
decoder: D,
body: B,
status_code: StatusCode,
encoding: Option<CompressionEncoding>,
max_message_size: Option<usize>,
) -> Self
where
B: Body + Send + 'static,
B::Error: Into<crate::Error>,
D: Decoder<Item = T, Error = Status> + Send + 'static,
{
Self::new(
decoder,
body,
Direction::Response(status_code),
encoding,
max_message_size,
)
}
pub(crate) fn new_empty<B, D>(decoder: D, body: B) -> Self
where
B: Body + Send + 'static,
B::Error: Into<crate::Error>,
D: Decoder<Item = T, Error = Status> + Send + 'static,
{
Self::new(decoder, body, Direction::EmptyResponse, None, None)
}
#[doc(hidden)]
pub fn new_request<B, D>(
decoder: D,
body: B,
encoding: Option<CompressionEncoding>,
max_message_size: Option<usize>,
) -> Self
where
B: Body + Send + 'static,
B::Error: Into<crate::Error>,
D: Decoder<Item = T, Error = Status> + Send + 'static,
{
Self::new(
decoder,
body,
Direction::Request,
encoding,
max_message_size,
)
}
fn new<B, D>(
decoder: D,
body: B,
direction: Direction,
encoding: Option<CompressionEncoding>,
max_message_size: Option<usize>,
) -> Self
where
B: Body + Send + 'static,
B::Error: Into<crate::Error>,
D: Decoder<Item = T, Error = Status> + Send + 'static,
{
Self {
decoder: Box::new(decoder),
inner: StreamingInner {
body: body
.map_data(|mut buf| buf.copy_to_bytes(buf.remaining()))
.map_err(|err| Status::map_error(err.into()))
.boxed_unsync(),
state: State::ReadHeader,
direction,
buf: BytesMut::with_capacity(BUFFER_SIZE),
trailers: None,
decompress_buf: BytesMut::new(),
encoding,
max_message_size,
},
}
}
}
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;
let limit = self
.max_message_size
.unwrap_or(DEFAULT_MAX_RECV_MESSAGE_SIZE);
if len > limit {
return Err(Status::new(
Code::OutOfRange,
format!(
"Error, message length too large: found {} bytes, the limit is: {} bytes",
len, limit
),
));
}
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(status)) => {
if self.direction == Direction::Request && status.code() == Code::Cancelled {
return Poll::Ready(Ok(None));
}
let _ = std::mem::replace(&mut self.state, State::Error);
debug!("decoder inner stream error: {:?}", status);
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, state: {:?}", self.state);
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(status) => {
debug!("decoder inner trailers error: {:?}", status);
return Poll::Ready(Err(status));
}
}
}
Poll::Ready(Ok(()))
}
}
impl<T> Streaming<T> {
/// Fetch the next message from this stream.
///
/// # Return value
///
/// - `Result::Err(val)` means a gRPC error was sent by the sender instead
/// of a valid response message. Refer to [`Status::code`] and
/// [`Status::message`] to examine possible error causes.
///
/// - `Result::Ok(None)` means the stream was closed by the sender and no
/// more messages will be delivered. Further attempts to call
/// [`Streaming::message`] will result in the same return value.
///
/// - `Result::Ok(Some(val))` means the sender streamed a valid response
/// message `val`.
///
/// ```rust
/// # use tonic::{Streaming, Status, codec::Decoder};
/// # use std::fmt::Debug;
/// # async fn next_message_ex<T, D>(mut request: Streaming<T>) -> Result<(), Status>
/// # where T: Debug,
/// # D: Decoder<Item = T, Error = Status> + Send + 'static,
/// # {
/// if let Some(next_message) = request.message().await? {
/// println!("{:?}", next_message);
/// }
/// # Ok(())
/// # }
/// ```
pub async fn message(&mut self) -> Result<Option<T>, Status> {
match future::poll_fn(|cx| Pin::new(&mut *self).poll_next(cx)).await {
Some(Ok(m)) => Ok(Some(m)),
Some(Err(e)) => Err(e),
None => Ok(None),
}
}
/// Fetch the trailing metadata.
///
/// This will drain the stream of all its messages to receive the trailing
/// metadata. If [`Streaming::message`] returns `None` then this function
/// will not need to poll for trailers since the body was totally consumed.
///
/// ```rust
/// # use tonic::{Streaming, Status};
/// # async fn trailers_ex<T>(mut request: Streaming<T>) -> Result<(), Status> {
/// if let Some(metadata) = request.trailers().await? {
/// println!("{:?}", metadata);
/// }
/// # Ok(())
/// # }
/// ```
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.inner.trailers.take() {
return Ok(Some(trailers));
}
// To fetch the trailers we must clear the body and drop it.
while self.message().await?.is_some() {}
// Since we call poll_trailers internally on poll_next we need to
// check if it got cached again.
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.inner.body).poll_trailers(cx))
.await
.map_err(|e| Status::from_error(Box::new(e)));
map.map(|x| x.map(MetadataMap::from_headers))
}
fn decode_chunk(&mut self) -> Result<Option<T>, Status> {
match self.inner.decode_chunk()? {
Some(mut decode_buf) => match self.decoder.decode(&mut decode_buf)? {
Some(msg) => {
self.inner.state = State::ReadHeader;
Ok(Some(msg))
}
None => Ok(None),
},
None => Ok(None),
}
}
}
impl<T> Stream for Streaming<T> {
type Item = Result<T, Status>;
fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
loop {
if let State::Error = &self.inner.state {
return Poll::Ready(None);
}
// FIXME: implement the ability to poll trailers when we _know_ that
// the consumer of this stream will only poll for the first message.
// This means we skip the poll_trailers step.
if let Some(item) = self.decode_chunk()? {
return Poll::Ready(Some(Ok(item)));
}
match ready!(self.inner.poll_data(cx))? {
Some(()) => (),
None => break,
}
}
Poll::Ready(match ready!(self.inner.poll_response(cx)) {
Ok(()) => None,
Err(err) => Some(Err(err)),
})
}
}
impl<T> fmt::Debug for Streaming<T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("Streaming").finish()
}
}
#[cfg(test)]
static_assertions::assert_impl_all!(Streaming<()>: Send);