Exec can return stdout data even after stdin is closed.

kube-client/src/api/remote_command.rs

@@ -12,10 +12,9 @@ use tokio::{
     io::{AsyncRead, AsyncWrite, AsyncWriteExt, DuplexStream},
     select,
 };
-use tokio_tungstenite::{
-    tungstenite::{self as ws},
-    WebSocketStream,
-};
+use tokio_tungstenite::tungstenite as ws;
+
+use crate::client::Connection;
 
 use super::AttachParams;
 
@@ -112,9 +111,7 @@ pub struct AttachedProcess {
 }
 
 impl AttachedProcess {
-    pub(crate) fn new<S>(stream: WebSocketStream<S>, ap: &AttachParams) -> Self
-    where
-        S: AsyncRead + AsyncWrite + Unpin + Sized + Send + 'static,
+    pub(crate) fn new(connection: Connection, ap: &AttachParams) -> Self
     {
         // To simplify the implementation, always create a pipe for stdin.
         // The caller does not have access to it unless they had requested.
@@ -140,7 +137,7 @@ impl AttachedProcess {
         };
 
         let task = tokio::spawn(start_message_loop(
-            stream,
+            connection,
             stdin_reader,
             stdout_writer,
             stderr_writer,
@@ -259,32 +256,37 @@ impl AttachedProcess {
     }
 }
 
-// theses values come from here: https://github.com/kubernetes/kubernetes/blob/master/pkg/kubelet/cri/streaming/remotecommand/websocket.go#L34
+// theses values come from here: https://github.com/kubernetes/kubernetes/blob/master/staging/src/k8s.io/apimachinery/pkg/util/remotecommand/constants.go#L57
 const STDIN_CHANNEL: u8 = 0;
 const STDOUT_CHANNEL: u8 = 1;
 const STDERR_CHANNEL: u8 = 2;
 // status channel receives `Status` object on exit.
 const STATUS_CHANNEL: u8 = 3;
 // resize channel is use to send TerminalSize object to change the size of the terminal
 const RESIZE_CHANNEL: u8 = 4;
+/// Used to signal that a channel has reached EOF. Only works on V5 of the protocol.
+const CLOSE_CHANNEL: u8 = 255;
 
-async fn start_message_loop<S>(
-    stream: WebSocketStream<S>,
+async fn start_message_loop(
+    connection: Connection,
     stdin: impl AsyncRead + Unpin,
     mut stdout: Option<impl AsyncWrite + Unpin>,
     mut stderr: Option<impl AsyncWrite + Unpin>,
     status_tx: StatusSender,
     mut terminal_size_rx: Option<TerminalSizeReceiver>,
 ) -> Result<(), Error>
-where
-    S: AsyncRead + AsyncWrite + Unpin + Sized + Send + 'static,
 {
+    let supports_stream_close = connection.supports_stream_close();
+    let stream = connection.into_stream();
     let mut stdin_stream = tokio_util::io::ReaderStream::new(stdin);
     let (mut server_send, raw_server_recv) = stream.split();
     // Work with filtered messages to reduce noise.
     let mut server_recv = raw_server_recv.filter_map(filter_message).boxed();
     let mut have_terminal_size_rx = terminal_size_rx.is_some();
 
+    // True until we reach EOF for stdin.
+    let mut stdin_is_open = true;
+
     loop {
         let terminal_size_next = async {
             match terminal_size_rx.as_mut() {
@@ -319,7 +321,7 @@ where
                     },
                 }
             },
-            stdin_message = stdin_stream.next() => {
+            stdin_message = stdin_stream.next(), if stdin_is_open => {
                 match stdin_message {
                     Some(Ok(bytes)) => {
                         if !bytes.is_empty() {
@@ -337,9 +339,24 @@ where
                     }
                     None => {
                         // Stdin closed (writer half dropped).
-                        // Let the server know and disconnect.
-                        server_send.close().await.map_err(Error::SendClose)?;
-                        break;
+                        // Let the server know we reached the end of stdin.
+                        if supports_stream_close {
+                            // Signal stdin has reached EOF.
+                            // See: https://github.com/kubernetes/kubernetes/blob/master/staging/src/k8s.io/apimachinery/pkg/util/httpstream/wsstream/conn.go#L346
+                            let vec = vec![CLOSE_CHANNEL, STDIN_CHANNEL];
+                            server_send
+                                .send(ws::Message::binary(vec))
+                                .await
+                                .map_err(Error::SendStdin)?;
+                        } else {
+                            // Best we can do is trigger the whole websocket to close.
+                            // We may miss out on any remaining stdout data that has not
+                            // been sent yet.
+                            server_send.close().await.map_err(Error::SendClose)?;
+                        }
+
+                        // Do not check stdin_stream for data in future loops.
+                        stdin_is_open = false;
                     }
                 }
             },

kube-client/src/api/subresource.rs

@@ -606,7 +606,7 @@ where
             .request
             .portforward(name, ports)
             .map_err(Error::BuildRequest)?;
-        let stream = self.client.connect(req).await?;
-        Ok(Portforwarder::new(stream, ports))
+        let connection = self.client.connect(req).await?;
+        Ok(Portforwarder::new(connection.into_stream(), ports))
     }
 }

kube-client/src/client/kubelet_debug.rs

@@ -69,8 +69,8 @@ impl Client {
         let mut req =
             Request::kubelet_node_portforward(kubelet_params, ports).map_err(Error::BuildRequest)?;
         req.extensions_mut().insert("kubelet_node_portforward");
-        let stream = self.connect(req).await?;
-        Ok(Portforwarder::new(stream, ports))
+        let connection = self.connect(req).await?;
+        Ok(Portforwarder::new(connection.into_stream(), ports))
     }
 
     /// Stream logs directly from node

kube-client/src/client/mod.rs

@@ -80,6 +80,29 @@ pub struct Client {
     default_ns: String,
 }
 
+/// Represents a WebSocket connection.
+/// Value returned by [`Client::connect`].
+#[cfg(feature = "ws")]
+#[cfg_attr(docsrs, doc(cfg(feature = "ws")))]
+pub struct Connection {
+    stream: WebSocketStream<TokioIo<hyper::upgrade::Upgraded>>,
+    protocol: upgrade::StreamProtocol,
+}
+
+#[cfg(feature = "ws")]
+#[cfg_attr(docsrs, doc(cfg(feature = "ws")))]
+impl Connection {
+    /// Return true if the stream supports graceful close signaling.
+    pub fn supports_stream_close(&self) -> bool {
+        self.protocol.supports_stream_close()
+    }
+
+    /// Transform into the raw WebSocketStream.
+    pub fn into_stream(self) -> WebSocketStream<TokioIo<hyper::upgrade::Upgraded>> {
+        self.stream
+    }
+}
+
 /// Constructors and low-level api interfaces.
 ///
 /// Most users only need [`Client::try_default`] or [`Client::new`] from this block.
@@ -193,7 +216,7 @@ impl Client {
     pub async fn connect(
         &self,
         request: Request<Vec<u8>>,
-    ) -> Result<WebSocketStream<TokioIo<hyper::upgrade::Upgraded>>> {
+    ) -> Result<Connection> {
         use http::header::HeaderValue;
         let (mut parts, body) = request.into_parts();
         parts
@@ -211,25 +234,18 @@ impl Client {
             http::header::SEC_WEBSOCKET_KEY,
             key.parse().expect("valid header value"),
         );
-        // Use the binary subprotocol v4, to get JSON `Status` object in `error` channel (3).
-        // There's no official documentation about this protocol, but it's described in
-        // [`k8s.io/apiserver/pkg/util/wsstream/conn.go`](https://git.io/JLQED).
-        // There's a comment about v4 and `Status` object in
-        // [`kublet/cri/streaming/remotecommand/httpstream.go`](https://git.io/JLQEh).
-        parts.headers.insert(
-            http::header::SEC_WEBSOCKET_PROTOCOL,
-            HeaderValue::from_static(upgrade::WS_PROTOCOL),
-        );
+        upgrade::StreamProtocol::add_to_headers(&mut parts.headers)?;
 
         let res = self.send(Request::from_parts(parts, Body::from(body))).await?;
-        upgrade::verify_response(&res, &key).map_err(Error::UpgradeConnection)?;
+        let protocol = upgrade::verify_response(&res, &key).map_err(Error::UpgradeConnection)?;
         match hyper::upgrade::on(res).await {
-            Ok(upgraded) => Ok(WebSocketStream::from_raw_socket(
+            Ok(upgraded) => Ok(Connection {
+                stream: WebSocketStream::from_raw_socket(
                 TokioIo::new(upgraded),
                 ws::protocol::Role::Client,
                 None,
             )
-            .await),
+            .await, protocol}),
 
             Err(e) => Err(Error::UpgradeConnection(
                 UpgradeConnectionError::GetPendingUpgrade(e),

kube-client/src/client/upgrade.rs

@@ -1,11 +1,82 @@
-use http::{self, Response, StatusCode};
+use http::{self, HeaderValue, Response, StatusCode};
 use thiserror::Error;
 use tokio_tungstenite::tungstenite as ws;
 
-use crate::client::Body;
+use crate::{client::Body, Error, Result};
 
-// Binary subprotocol v4. See `Client::connect`.
-pub const WS_PROTOCOL: &str = "v4.channel.k8s.io";
+#[derive(Debug)]
+pub enum StreamProtocol {
+    /// Binary subprotocol v4. See `Client::connect`.
+    V4,
+
+    /// Binary subprotocol v5. See `Client::connect`.
+    /// v5 supports CLOSE signals.
+    /// https://github.com/kubernetes/kubernetes/blob/master/staging/src/k8s.io/apimachinery/pkg/util/remotecommand/constants.go#L52C26-L52C43
+    V5,
+}
+
+impl StreamProtocol {
+    pub fn as_str(&self) -> &'static str {
+        match self {
+            StreamProtocol::V4 => "v4.channel.k8s.io",
+            StreamProtocol::V5 => "v5.channel.k8s.io"
+        }
+    }
+
+    fn as_bytes(&self) -> &'static [u8] {
+        self.as_str().as_bytes()
+    }
+
+    pub fn supports_stream_close(&self) -> bool {
+        match self {
+            StreamProtocol::V4 => false,
+            StreamProtocol::V5 => true
+        }
+    }
+
+    /// Add HTTP header SEC_WEBSOCKET_PROTOCOL with a list of supported protocol.
+    pub fn add_to_headers(headers: &mut http::HeaderMap) -> Result<()> {
+        // Protocols we support in our preferred order.
+        let supported_protocols = vec![
+            // v5 supports CLOSE signals.
+            StreamProtocol::V5.as_str(),
+            // Use the binary subprotocol v4, to get JSON `Status` object in `error` channel (3).
+            // There's no official documentation about this protocol, but it's described in
+            // [`k8s.io/apiserver/pkg/util/wsstream/conn.go`](https://git.io/JLQED).
+            // There's a comment about v4 and `Status` object in
+            // [`kublet/cri/streaming/remotecommand/httpstream.go`](https://git.io/JLQEh).
+            StreamProtocol::V4.as_str(),
+        ];
+
+        let header_value_string = supported_protocols.join(", ");
+
+        // Note: Multiple headers does not work. Only a single CSV works.
+        headers.insert(
+            http::header::SEC_WEBSOCKET_PROTOCOL,
+            HeaderValue::from_str(&header_value_string).map_err(|e| Error::HttpError(e.into()))?,
+        );
+
+        Ok(())
+    }
+
+    /// Return the subprotocol of an HTTP response.
+    fn get_from_response<B>(res: &Response<B>) -> Option<Self> {
+        let headers = res.headers();
+
+        match headers
+            .get(http::header::SEC_WEBSOCKET_PROTOCOL)
+            .map(|h| h.as_bytes()) {
+                Some(protocol) => if protocol == StreamProtocol::V4.as_bytes() {
+                    Some(StreamProtocol::V4)
+                } else if protocol == StreamProtocol::V5.as_bytes() {
+                    Some(StreamProtocol::V5)
+                } else {
+                    None
+                },
+                _ => None,
+            }
+    }
+}
 
 /// Possible errors from upgrading to a WebSocket connection
 #[cfg(feature = "ws")]
@@ -42,7 +113,7 @@ pub enum UpgradeConnectionError {
 
 // Verify upgrade response according to RFC6455.
 // Based on `tungstenite` and added subprotocol verification.
-pub fn verify_response(res: &Response<Body>, key: &str) -> Result<(), UpgradeConnectionError> {
+pub fn verify_response(res: &Response<Body>, key: &str) -> Result<StreamProtocol, UpgradeConnectionError> {
     if res.status() != StatusCode::SWITCHING_PROTOCOLS {
         return Err(UpgradeConnectionError::ProtocolSwitch(res.status()));
     }
@@ -75,14 +146,11 @@ pub fn verify_response(res: &Response<Body>, key: &str) -> Result<(), UpgradeCon
         return Err(UpgradeConnectionError::SecWebSocketAcceptKeyMismatch);
     }
 
-    // Make sure that the server returned the correct subprotocol.
-    if !headers
-        .get(http::header::SEC_WEBSOCKET_PROTOCOL)
-        .map(|h| h == WS_PROTOCOL)
-        .unwrap_or(false)
-    {
-        return Err(UpgradeConnectionError::SecWebSocketProtocolMismatch);
-    }
+    // Make sure that the server returned an expected subprotocol.
+    let protocol = match StreamProtocol::get_from_response(res) {
+        Some(p) => p,
+        None => return Err(UpgradeConnectionError::SecWebSocketProtocolMismatch)
+    };
 
-    Ok(())
+    Ok(protocol)
 }

kube-client/src/lib.rs

@@ -279,6 +279,7 @@ mod test {
     #[cfg(feature = "ws")]
     async fn pod_can_exec_and_write_to_stdin() -> Result<(), Box<dyn std::error::Error>> {
         use crate::api::{DeleteParams, ListParams, Patch, PatchParams, WatchEvent};
+        use tokio::io::AsyncWriteExt;
 
         let client = Client::try_default().await?;
         let pods: Api<Pod> = Api::default_namespaced(client);
@@ -348,9 +349,42 @@ mod test {
             assert_eq!(out, "1\n2\n3\n");
         }
 
+        // Verify we read from stdout after stdin is closed.
+        {
+            let name = "busybox-kube2";
+            let command = vec!["sh", "-c", "sleep 2; echo test string 2"];
+            let ap = AttachParams::default().stdin(true).stderr(false);
+
+            // Make a connection so we can determine if the K8s cluster supports stream closing.
+            let mut req = pods.request.exec(name, command.clone(), &ap)?;
+            req.extensions_mut().insert("exec");
+            let stream = pods.client.connect(req).await?;
+
+            // This only works is the cluster supports protocol version v5.channel.k8s.io
+            // Skip for older protocols.
+            if stream.supports_stream_close() {
+                let mut attached = pods.exec(name, command, &ap).await?;
+                let mut stdin_writer = attached.stdin().unwrap();
+                let mut stdout_stream = tokio_util::io::ReaderStream::new(attached.stdout().unwrap());
+
+                stdin_writer.write_all(b"this will be ignored\n").await?;
+                _ = stdin_writer.shutdown().await;
+
+                let next_stdout = stdout_stream.next();
+                let stdout = String::from_utf8(next_stdout.await.unwrap().unwrap().to_vec()).unwrap();
+                assert_eq!(stdout, "test string 2\n");
+
+                // AttachedProcess resolves with status object.
+                let status = attached.take_status().unwrap();
+                if let Some(status) = status.await {
+                    assert_eq!(status.status, Some("Success".to_owned()));
+                    assert_eq!(status.reason, None);
+                }
+            }
+        }
+
         // Verify we can write to Stdin
         {
-            use tokio::io::AsyncWriteExt;
             let mut attached = pods
                 .exec(
                     "busybox-kube2",