fix(streamable-http): gracefully shutdown while client connected

crates/rmcp/src/transport/common/server_side_http.rs

@@ -6,6 +6,7 @@ use http::Response;
 use http_body::Body;
 use http_body_util::{BodyExt, Empty, Full, combinators::BoxBody};
 use sse_stream::{KeepAlive, Sse, SseBody};
+use tokio_util::sync::CancellationToken;
 
 use super::http_header::EVENT_STREAM_MIME_TYPE;
 use crate::model::{ClientJsonRpcMessage, ServerJsonRpcMessage};
@@ -65,20 +66,26 @@ pub struct ServerSseMessage {
 pub(crate) fn sse_stream_response(
     stream: impl futures::Stream<Item = ServerSseMessage> + Send + Sync + 'static,
     keep_alive: Option<Duration>,
+    ct: CancellationToken,
 ) -> Response<BoxBody<Bytes, Infallible>> {
     use futures::StreamExt;
-    let stream = SseBody::new(stream.map(|message| {
-        let data = serde_json::to_string(&message.message).expect("valid message");
-        let mut sse = Sse::default().data(data);
-        sse.id = message.event_id;
-        Result::<Sse, Infallible>::Ok(sse)
-    }));
+    let stream = stream
+        .map(|message| {
+            let data = serde_json::to_string(&message.message).expect("valid message");
+            let mut sse = Sse::default().data(data);
+            sse.id = message.event_id;
+            Result::<Sse, Infallible>::Ok(sse)
+        })
+        .take_until(async move { ct.cancelled().await });
+    let stream = SseBody::new(stream);
+
     let stream = match keep_alive {
         Some(duration) => stream
             .with_keep_alive::<TokioTimer>(KeepAlive::new().interval(duration))
             .boxed(),
         None => stream.boxed(),
     };
+
     Response::builder()
         .status(http::StatusCode::OK)
         .header(http::header::CONTENT_TYPE, EVENT_STREAM_MIME_TYPE)

crates/rmcp/src/transport/streamable_http_server/tower.rs

@@ -6,6 +6,7 @@ use http::{Method, Request, Response, header::ALLOW};
 use http_body::Body;
 use http_body_util::{BodyExt, Full, combinators::BoxBody};
 use tokio_stream::wrappers::ReceiverStream;
+use tokio_util::sync::CancellationToken;
 
 use super::session::SessionManager;
 use crate::{
@@ -33,13 +34,15 @@ pub struct StreamableHttpServerConfig {
     pub sse_keep_alive: Option<Duration>,
     /// If true, the server will create a session for each request and keep it alive.
     pub stateful_mode: bool,
+    pub cancellation_token: CancellationToken,
 }
 
 impl Default for StreamableHttpServerConfig {
     fn default() -> Self {
         Self {
             sse_keep_alive: Some(Duration::from_secs(15)),
             stateful_mode: true,
+            cancellation_token: CancellationToken::new(),
         }
     }
 }
@@ -209,15 +212,23 @@ where
                 .resume(&session_id, last_event_id)
                 .await
                 .map_err(internal_error_response("resume session"))?;
-            Ok(sse_stream_response(stream, self.config.sse_keep_alive))
+            Ok(sse_stream_response(
+                stream,
+                self.config.sse_keep_alive,
+                self.config.cancellation_token.child_token(),
+            ))
         } else {
             // create standalone stream
             let stream = self
                 .session_manager
                 .create_standalone_stream(&session_id)
                 .await
                 .map_err(internal_error_response("create standalone stream"))?;
-            Ok(sse_stream_response(stream, self.config.sse_keep_alive))
+            Ok(sse_stream_response(
+                stream,
+                self.config.sse_keep_alive,
+                self.config.cancellation_token.child_token(),
+            ))
         }
     }
 
@@ -307,7 +318,11 @@ where
                             .create_stream(&session_id, message)
                             .await
                             .map_err(internal_error_response("get session"))?;
-                        Ok(sse_stream_response(stream, self.config.sse_keep_alive))
+                        Ok(sse_stream_response(
+                            stream,
+                            self.config.sse_keep_alive,
+                            self.config.cancellation_token.child_token(),
+                        ))
                     }
                     ClientJsonRpcMessage::Notification(_)
                     | ClientJsonRpcMessage::Response(_)
@@ -380,6 +395,7 @@ where
                         }
                     }),
                     self.config.sse_keep_alive,
+                    self.config.cancellation_token.child_token(),
                 );
 
                 response.headers_mut().insert(
@@ -413,6 +429,7 @@ where
                             }
                         }),
                         self.config.sse_keep_alive,
+                        self.config.cancellation_token.child_token(),
                     ))
                 }
                 ClientJsonRpcMessage::Notification(_notification) => {

examples/servers/src/counter_streamhttp.rs

@@ -1,5 +1,6 @@
-use rmcp::transport::streamable_http_server::{
-    StreamableHttpService, session::local::LocalSessionManager,
+use rmcp::transport::{
+    StreamableHttpServerConfig,
+    streamable_http_server::{StreamableHttpService, session::local::LocalSessionManager},
 };
 use tracing_subscriber::{
     layer::SubscriberExt,
@@ -20,17 +21,24 @@ async fn main() -> anyhow::Result<()> {
         )
         .with(tracing_subscriber::fmt::layer())
         .init();
+    let ct = tokio_util::sync::CancellationToken::new();
 
     let service = StreamableHttpService::new(
         || Ok(Counter::new()),
         LocalSessionManager::default().into(),
-        Default::default(),
+        StreamableHttpServerConfig {
+            cancellation_token: ct.child_token(),
+            ..Default::default()
+        },
     );
 
     let router = axum::Router::new().nest_service("/mcp", service);
     let tcp_listener = tokio::net::TcpListener::bind(BIND_ADDRESS).await?;
     let _ = axum::serve(tcp_listener, router)
-        .with_graceful_shutdown(async { tokio::signal::ctrl_c().await.unwrap() })
+        .with_graceful_shutdown(async move {
+            tokio::signal::ctrl_c().await.unwrap();
+            ct.cancel();
+        })
         .await;
     Ok(())
 }