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fix:avoid streamable listening sse duplicate creation #524

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fix:avoid streamable listening sse duplicate creation #524

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3dac307
avoid streamable listening sse duplicate creation
taobaorun Aug 28, 2025
c7cbe98
Listening stream already exists for this session and will be closed t…
taobaorun Aug 31, 2025
e87387b
Atomically close the existing listening stream and switch to the new …
taobaorun Sep 1, 2025
4b30e0a
fix listening sse stream close blocking
taobaorun Sep 3, 2025
90ecbb4
resolve conflicts
taobaorun Sep 3, 2025
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11 changes: 10 additions & 1 deletion ...va/io/modelcontextprotocol/server/transport/WebFluxStreamableServerTransportProvider.java
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Original file line number Diff line number Diff line change
Expand Up @@ -10,8 +10,10 @@
import io.modelcontextprotocol.server.McpTransportContextExtractor;
import io.modelcontextprotocol.spec.HttpHeaders;
import io.modelcontextprotocol.spec.McpError;
import io.modelcontextprotocol.spec.McpLoggableSession;
import io.modelcontextprotocol.spec.McpSchema;
import io.modelcontextprotocol.spec.McpStreamableServerSession;
import io.modelcontextprotocol.spec.McpStreamableServerSession.McpStreamableServerSessionStream;
import io.modelcontextprotocol.spec.McpStreamableServerTransport;
import io.modelcontextprotocol.spec.McpStreamableServerTransportProvider;
import io.modelcontextprotocol.spec.ProtocolVersions;
Expand Down Expand Up @@ -187,12 +189,19 @@ private Mono<ServerResponse> handleGet(ServerRequest request) {
return ServerResponse.notFound().build();
}

McpLoggableSession listenedStream = session.getListeningStream();
if (request.headers().asHttpHeaders().containsKey(HttpHeaders.LAST_EVENT_ID)) {
String lastId = request.headers().asHttpHeaders().getFirst(HttpHeaders.LAST_EVENT_ID);
return ServerResponse.ok()
.contentType(MediaType.TEXT_EVENT_STREAM)
.body(session.replay(lastId), ServerSentEvent.class);
}
if (listenedStream instanceof McpStreamableServerSessionStream) {
logger.debug(
"Listening stream already exists for this session:{} and will be closed to make way for the new listening SSE stream",
sessionId);
listenedStream.close();
}

return ServerResponse.ok()
.contentType(MediaType.TEXT_EVENT_STREAM)
Expand Down Expand Up @@ -484,4 +493,4 @@ public WebFluxStreamableServerTransportProvider build() {

}

}
}
11 changes: 9 additions & 2 deletions ...ava/io/modelcontextprotocol/server/transport/WebMvcStreamableServerTransportProvider.java
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,8 @@
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.locks.ReentrantLock;

import io.modelcontextprotocol.spec.McpLoggableSession;
import io.modelcontextprotocol.spec.McpStreamableServerSession.McpStreamableServerSessionStream;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.HttpStatus;
Expand Down Expand Up @@ -252,7 +254,6 @@ private ServerResponse handleGet(ServerRequest request) {
}

logger.debug("Handling GET request for session: {}", sessionId);

try {
return ServerResponse.sse(sseBuilder -> {
sseBuilder.onTimeout(() -> {
Expand All @@ -265,7 +266,6 @@ private ServerResponse handleGet(ServerRequest request) {
// Check if this is a replay request
if (request.headers().asHttpHeaders().containsKey(HttpHeaders.LAST_EVENT_ID)) {
String lastId = request.headers().asHttpHeaders().getFirst(HttpHeaders.LAST_EVENT_ID);

try {
session.replay(lastId)
.contextWrite(ctx -> ctx.put(McpTransportContext.KEY, transportContext))
Expand All @@ -288,6 +288,13 @@ private ServerResponse handleGet(ServerRequest request) {
}
}
else {
McpLoggableSession listenedStream = session.getListeningStream();
if (listenedStream instanceof McpStreamableServerSessionStream) {
logger.debug(
"Listening stream already exists for this session:{} and will be closed to make way for the new listening SSE stream",
sessionId);
listenedStream.close();
}
// Establish new listening stream
McpStreamableServerSession.McpStreamableServerSessionStream listeningStream = session
.listeningStream(sessionTransport);
Expand Down
10 changes: 9 additions & 1 deletion ...o/modelcontextprotocol/server/transport/HttpServletStreamableServerTransportProvider.java
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,8 @@
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.locks.ReentrantLock;

import io.modelcontextprotocol.spec.McpLoggableSession;
import io.modelcontextprotocol.spec.McpStreamableServerSession.McpStreamableServerSessionStream;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

Expand Down Expand Up @@ -273,7 +275,6 @@ protected void doGet(HttpServletRequest request, HttpServletResponse response)
}

logger.debug("Handling GET request for session: {}", sessionId);

McpTransportContext transportContext = this.contextExtractor.extract(request, new DefaultMcpTransportContext());

try {
Expand Down Expand Up @@ -315,6 +316,13 @@ protected void doGet(HttpServletRequest request, HttpServletResponse response)
}
}
else {
McpLoggableSession listenedStream = session.getListeningStream();
if (listenedStream instanceof McpStreamableServerSessionStream) {
logger.debug(
"Listening stream already exists for this session:{} and will be closed to make way for the new listening SSE stream",
sessionId);
listenedStream.close();
}
// Establish new listening stream
McpStreamableServerSession.McpStreamableServerSessionStream listeningStream = session
.listeningStream(sessionTransport);
Expand Down
4 changes: 4 additions & 0 deletions mcp/src/main/java/io/modelcontextprotocol/spec/McpStreamableServerSession.java
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Original file line number Diff line number Diff line change
Expand Up @@ -142,6 +142,10 @@ public McpStreamableServerSessionStream listeningStream(McpStreamableServerTrans
return listeningStream;
}

public McpLoggableSession getListeningStream() {
return this.listeningStreamRef.get();
}

// TODO: keep track of history by keeping a map from eventId to stream and then
// iterate over the events using the lastEventId
public Flux<McpSchema.JSONRPCMessage> replay(Object lastEventId) {
Expand Down