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Implement SEP-1699: Support SSE Polling via Server-Side Disconnect (#604)

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* feat: implement SEP-1699 SSE polling via server-side disconnect

* test: add tests for priming behavior on stream start and close
This commit is contained in:
Dale Seo 2026-01-09 13:22:57 -05:00 • committed by GitHub
commit 971c64c31f
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1 changed files with 397 additions and 22 deletions
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77
crates/rmcp/src/transport/streamable_http_server/tower.rs
View file

@ -32,7 +32,10 @@ use crate::{
pub struct StreamableHttpServerConfig {
/// The ping message duration for SSE connections.
pub sse_keep_alive: Option<Duration>,
/// The retry interval for SSE priming events.
pub sse_retry: Option<Duration>,
/// If true, the server will create a session for each request and keep it alive.
/// When enabled, SSE priming events are sent to enable client reconnection.
pub stateful_mode: bool,
/// Cancellation token for the Streamable HTTP server.
///
@ -45,6 +48,7 @@ impl Default for StreamableHttpServerConfig {
fn default() -> Self {
Self {
sse_keep_alive: Some(Duration::from_secs(15)),
sse_retry: Some(Duration::from_secs(3)),
stateful_mode: true,
cancellation_token: CancellationToken::new(),
}
@ -216,6 +220,7 @@ where
.resume(&session_id, last_event_id)
.await
.map_err(internal_error_response("resume session"))?;
// Resume doesn't need priming - client already has the event ID
Ok(sse_stream_response(
stream,
self.config.sse_keep_alive,
@ -228,6 +233,19 @@ where
.create_standalone_stream(&session_id)
.await
.map_err(internal_error_response("create standalone stream"))?;
// Prepend priming event if sse_retry configured
let stream = if let Some(retry) = self.config.sse_retry {
let priming = ServerSseMessage {
event_id: Some("0".into()),
message: None,
retry: Some(retry),
};
futures::stream::once(async move { priming })
.chain(stream)
.left_stream()
} else {
stream.right_stream()
};
Ok(sse_stream_response(
stream,
self.config.sse_keep_alive,
@ -322,6 +340,19 @@ where
.create_stream(&session_id, message)
.await
.map_err(internal_error_response("get session"))?;
// Prepend priming event if sse_retry configured
let stream = if let Some(retry) = self.config.sse_retry {
let priming = ServerSseMessage {
event_id: Some("0".into()),
message: None,
retry: Some(retry),
};
futures::stream::once(async move { priming })
.chain(stream)
.left_stream()
} else {
stream.right_stream()
};
Ok(sse_stream_response(
stream,
self.config.sse_keep_alive,
@ -389,15 +420,28 @@ where
.initialize_session(&session_id, message)
.await
.map_err(internal_error_response("create stream"))?;
let stream = futures::stream::once(async move {
ServerSseMessage {
event_id: None,
message: Some(Arc::new(response)),
retry: None,
}
});
// Prepend priming event if sse_retry configured
let stream = if let Some(retry) = self.config.sse_retry {
let priming = ServerSseMessage {
event_id: Some("0".into()),
message: None,
retry: Some(retry),
};
futures::stream::once(async move { priming })
.chain(stream)
.left_stream()
} else {
stream.right_stream()
};
let mut response = sse_stream_response(
futures::stream::once({
async move {
ServerSseMessage {
event_id: None,
message: response.into(),
}
}
}),
stream,
self.config.sse_keep_alive,
self.config.cancellation_token.child_token(),
);
@ -424,14 +468,17 @@ where
// on service created
let _ = service.waiting().await;
});
// Stateless mode: no priming (no session to resume)
let stream = ReceiverStream::new(receiver).map(|message| {
tracing::info!(?message);
ServerSseMessage {
event_id: None,
message: Some(Arc::new(message)),
retry: None,
}
});
Ok(sse_stream_response(
ReceiverStream::new(receiver).map(|message| {
tracing::info!(?message);
ServerSseMessage {
event_id: None,
message: message.into(),
}
}),
stream,
self.config.sse_keep_alive,
self.config.cancellation_token.child_token(),
))