Use bounded channels on receive side for backpressure

src/client.rs

@@ -8,7 +8,6 @@ use async_trait::async_trait;
 use bytes::Bytes;
 use log::{debug, error, trace};
 
-use futures::channel::mpsc::{unbounded, UnboundedReceiver};
 use futures::io::AsyncReadExt;
 use kuska_handshake::async_std::{handshake_client, BoxStream};
 use tokio::net::TcpStream;
@@ -39,7 +38,7 @@ pub(crate) struct ClientConn {
 	query_send: ArcSwapOption<mpsc::UnboundedSender<(RequestID, RequestPriority, ByteStream)>>,
 
 	next_query_number: AtomicU32,
-	inflight: Mutex<HashMap<RequestID, oneshot::Sender<UnboundedReceiver<Packet>>>>,
+	inflight: Mutex<HashMap<RequestID, oneshot::Sender<ByteStream>>>,
 }
 
 impl ClientConn {
@@ -175,7 +174,9 @@ impl ClientConn {
 			error!(
 				"Too many inflight requests! RequestID collision. Interrupting previous request."
 			);
-			let _ = old_ch.send(unbounded().1);
+			let _ = old_ch.send(Box::pin(futures::stream::once(async move {
+				Err(Error::IdCollision.code())
+			})));
 		}
 
 		trace!(
@@ -199,7 +200,7 @@ impl ClientConn {
 			}
 		}
 
-		let resp_enc = RespEnc::decode(Box::pin(stream)).await?;
+		let resp_enc = RespEnc::decode(stream).await?;
 		trace!("request response {}", id);
 		Resp::from_enc(resp_enc)
 	}
@@ -209,7 +210,7 @@ impl SendLoop for ClientConn {}
 
 #[async_trait]
 impl RecvLoop for ClientConn {
-	fn recv_handler(self: &Arc<Self>, id: RequestID, stream: UnboundedReceiver<Packet>) {
+	fn recv_handler(self: &Arc<Self>, id: RequestID, stream: ByteStream) {
 		trace!("ClientConn recv_handler {}", id);
 
 		let mut inflight = self.inflight.lock().unwrap();

src/error.rs

@@ -28,6 +28,9 @@ pub enum Error {
 	#[error(display = "Framing protocol error")]
 	Framing,
 
+	#[error(display = "Request ID collision")]
+	IdCollision,
+
 	#[error(display = "{}", _0)]
 	Message(String),
 
@@ -56,6 +59,7 @@ impl Error {
 			Self::Framing => 13,
 			Self::NoHandler => 20,
 			Self::ConnectionClosed => 21,
+			Self::IdCollision => 22,
 			Self::Handshake(_) => 30,
 			Self::VersionMismatch(_) => 31,
 			Self::Remote(c, _) => *c,

src/recv.rs

@@ -5,8 +5,8 @@ use async_trait::async_trait;
 use bytes::Bytes;
 use log::trace;
 
-use futures::channel::mpsc::{unbounded, UnboundedReceiver, UnboundedSender};
 use futures::AsyncReadExt;
+use tokio::sync::mpsc;
 
 use crate::error::*;
 use crate::send::*;
@@ -15,33 +15,28 @@ use crate::stream::*;
 /// Structure to warn when the sender is dropped before end of stream was reached, like when
 /// connection to some remote drops while transmitting data
 struct Sender {
-	inner: UnboundedSender<Packet>,
-	closed: bool,
+	inner: Option<mpsc::Sender<Packet>>,
 }
 
 impl Sender {
-	fn new(inner: UnboundedSender<Packet>) -> Self {
-		Sender {
-			inner,
-			closed: false,
-		}
+	fn new(inner: mpsc::Sender<Packet>) -> Self {
+		Sender { inner: Some(inner) }
 	}
 
-	fn send(&self, packet: Packet) {
-		let _ = self.inner.unbounded_send(packet);
+	async fn send(&self, packet: Packet) {
+		let _ = self.inner.as_ref().unwrap().send(packet).await;
 	}
 
 	fn end(&mut self) {
-		self.closed = true;
+		self.inner = None;
 	}
 }
 
 impl Drop for Sender {
 	fn drop(&mut self) {
-		if !self.closed {
-			self.send(Err(255));
+		if let Some(inner) = self.inner.take() {
+			let _ = inner.blocking_send(Err(255));
 		}
-		self.inner.close_channel();
 	}
 }
 
@@ -54,7 +49,7 @@ impl Drop for Sender {
 /// the full message is passed to the receive handler.
 #[async_trait]
 pub(crate) trait RecvLoop: Sync + 'static {
-	fn recv_handler(self: &Arc<Self>, id: RequestID, stream: UnboundedReceiver<Packet>);
+	fn recv_handler(self: &Arc<Self>, id: RequestID, stream: ByteStream);
 
 	async fn recv_loop<R>(self: Arc<Self>, mut read: R) -> Result<(), Error>
 	where
@@ -92,14 +87,17 @@ pub(crate) trait RecvLoop: Sync + 'static {
 			let mut sender = if let Some(send) = streams.remove(&(id)) {
 				send
 			} else {
-				let (send, recv) = unbounded();
-				self.recv_handler(id, recv);
+				let (send, recv) = mpsc::channel(4);
+				self.recv_handler(
+					id,
+					Box::pin(tokio_stream::wrappers::ReceiverStream::new(recv)),
+				);
 				Sender::new(send)
 			};
 
-			// if we get an error, the receiving end is disconnected. We still need to
-			// reach eos before dropping this sender
-			sender.send(packet);
+			// If we get an error, the receiving end is disconnected.
+			// We still need to reach eos before dropping this sender
+			let _ = sender.send(packet).await;
 
 			if has_cont {
 				streams.insert(id, sender);

src/server.rs

@@ -5,7 +5,6 @@ use arc_swap::ArcSwapOption;
 use async_trait::async_trait;
 use log::{debug, trace};
 
-use futures::channel::mpsc::UnboundedReceiver;
 use futures::io::{AsyncReadExt, AsyncWriteExt};
 use kuska_handshake::async_std::{handshake_server, BoxStream};
 use tokio::net::TcpStream;
@@ -171,21 +170,24 @@ impl SendLoop for ServerConn {}
 
 #[async_trait]
 impl RecvLoop for ServerConn {
-	fn recv_handler(self: &Arc<Self>, id: RequestID, stream: UnboundedReceiver<Packet>) {
+	fn recv_handler(self: &Arc<Self>, id: RequestID, stream: ByteStream) {
 		let resp_send = self.resp_send.load_full().unwrap();
 
 		let self2 = self.clone();
 		tokio::spawn(async move {
 			trace!("ServerConn recv_handler {}", id);
-			let (prio, resp_enc) = match ReqEnc::decode(Box::pin(stream)).await {
+			let (prio, resp_enc) = match ReqEnc::decode(stream).await {
 				Ok(req_enc) => {
 					let prio = req_enc.prio;
 					let resp = self2.recv_handler_aux(req_enc).await;
 
-					(prio, match resp {
-						Ok(resp_enc) => resp_enc,
-						Err(e) => RespEnc::from_err(e),
-					})
+					(
+						prio,
+						match resp {
+							Ok(resp_enc) => resp_enc,
+							Err(e) => RespEnc::from_err(e),
+						},
+					)
 				}
 				Err(e) => (PRIO_NORMAL, RespEnc::from_err(e)),
 			};