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Close servlet streamable HTTP transports on async lifecycle events #1027

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Close servlet streamable HTTP transports on async lifecycle events #1027

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66 changes: 35 additions & 31 deletions ...o/modelcontextprotocol/server/transport/HttpServletStreamableServerTransportProvider.java
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,8 @@
import io.modelcontextprotocol.json.McpJsonMapper;
import io.modelcontextprotocol.util.KeepAliveScheduler;
import jakarta.servlet.AsyncContext;
import jakarta.servlet.AsyncEvent;
import jakarta.servlet.AsyncListener;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
Expand Down Expand Up @@ -317,6 +319,7 @@ protected void doGet(HttpServletRequest request, HttpServletResponse response)
// Check if this is a replay request
if (request.getHeader(HttpHeaders.LAST_EVENT_ID) != null) {
String lastId = request.getHeader(HttpHeaders.LAST_EVENT_ID);
registerAsyncLifecycle(asyncContext, sessionId, sessionTransport::close);

try {
session.replay(lastId)
Expand All @@ -330,44 +333,21 @@ protected void doGet(HttpServletRequest request, HttpServletResponse response)
}
catch (Exception e) {
logger.error("Failed to replay message: {}", e.getMessage());
asyncContext.complete();
sessionTransport.close();
}
});
}
catch (Exception e) {
logger.error("Failed to replay messages: {}", e.getMessage());
asyncContext.complete();
sessionTransport.close();
}
}
else {
// Establish new listening stream
McpStreamableServerSession.McpStreamableServerSessionStream listeningStream = session
.listeningStream(sessionTransport);

asyncContext.addListener(new jakarta.servlet.AsyncListener() {
@Override
public void onComplete(jakarta.servlet.AsyncEvent event) throws IOException {
logger.debug("SSE connection completed for session: {}", sessionId);
listeningStream.close();
}

@Override
public void onTimeout(jakarta.servlet.AsyncEvent event) throws IOException {
logger.debug("SSE connection timed out for session: {}", sessionId);
listeningStream.close();
}

@Override
public void onError(jakarta.servlet.AsyncEvent event) throws IOException {
logger.debug("SSE connection error for session: {}", sessionId);
listeningStream.close();
}

@Override
public void onStartAsync(jakarta.servlet.AsyncEvent event) throws IOException {
// No action needed
}
});
registerAsyncLifecycle(asyncContext, sessionId, listeningStream::close);
}
}
catch (Exception e) {
Expand Down Expand Up @@ -519,6 +499,7 @@ else if (message instanceof McpSchema.JSONRPCRequest jsonrpcRequest) {

HttpServletStreamableMcpSessionTransport sessionTransport = new HttpServletStreamableMcpSessionTransport(
sessionId, asyncContext, response.getWriter());
registerAsyncLifecycle(asyncContext, sessionId, sessionTransport::close);

try {
session.responseStream(jsonrpcRequest, sessionTransport)
Expand All @@ -527,7 +508,7 @@ else if (message instanceof McpSchema.JSONRPCRequest jsonrpcRequest) {
}
catch (Exception e) {
logger.error("Failed to handle request stream: {}", e.getMessage());
asyncContext.complete();
sessionTransport.close();
}
}
else {
Expand Down Expand Up @@ -557,6 +538,32 @@ else if (message instanceof McpSchema.JSONRPCRequest jsonrpcRequest) {
}
}

private void registerAsyncLifecycle(AsyncContext asyncContext, String sessionId, Runnable onClose) {
asyncContext.addListener(new AsyncListener() {
@Override
public void onComplete(AsyncEvent event) throws IOException {
logger.debug("SSE async context completed for session: {}", sessionId);
onClose.run();
}

@Override
public void onTimeout(AsyncEvent event) throws IOException {
logger.debug("SSE async context timed out for session: {}", sessionId);
onClose.run();
}

@Override
public void onError(AsyncEvent event) throws IOException {
logger.debug("SSE async context errored for session: {}", sessionId);
onClose.run();
}

@Override
public void onStartAsync(AsyncEvent event) throws IOException {
}
});
}

/**
* Handles DELETE requests for session deletion.
* @param request The HTTP servlet request
Expand Down Expand Up @@ -747,8 +754,7 @@ public Mono<Void> sendMessage(McpSchema.JSONRPCMessage message, String messageId
}
catch (Exception e) {
logger.error("Failed to send message to session {}: {}", this.sessionId, e.getMessage());
HttpServletStreamableServerTransportProvider.this.sessions.remove(this.sessionId);
this.asyncContext.complete();
this.close();
}
finally {
lock.unlock();
Expand Down Expand Up @@ -792,8 +798,6 @@ public void close() {
}

this.closed = true;

// HttpServletStreamableServerTransportProvider.this.sessions.remove(this.sessionId);
this.asyncContext.complete();
logger.debug("Successfully completed async context for session {}", sessionId);
}
Expand Down
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