fix: health check for mcp server (#8908)

* fix health check for mcp server

* [autofix.ci] apply automated fixes

---------

Co-authored-by: phact <estevez.sebastian@gmail.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

src/backend/base/langflow/base/mcp/util.py

@@ -387,17 +387,26 @@ class MCPSessionManager:
             try:
                 session = session_info["session"]
                 task = session_info["task"]
-                if (
+
-                    not task.done()
+                # Break down the health check to understand why cleanup is triggered
-                    and hasattr(session, "_closed")
+                task_not_done = not task.done()
-                    and not session._closed
+
-                    and hasattr(session, "_write_stream")
+                logger.debug(f"Session health check for context_id {context_id}:")
-                    and hasattr(session._write_stream, "_closed")
+                logger.debug(f"  - task_not_done: {task_not_done}")
-                    and not session._write_stream._closed
+
-                ):
+                # For MCP ClientSession, we rely on the background task being alive
+                session_is_healthy = task_not_done
+
+                logger.debug(f"  - session_is_healthy: {session_is_healthy}")
+
+                if session_is_healthy:
+                    logger.debug(f"Session for context_id {context_id} is healthy, reusing")
                     return session
-            except Exception:  # noqa: BLE001
+                msg = f"Session for context_id {context_id} failed health check: background task is done"
-                msg = f"Session for context_id {context_id} is dead"
+                logger.info(msg)
+
+            except Exception as e:  # noqa: BLE001
+                msg = f"Session for context_id {context_id} is dead due to exception: {e}"
                 logger.info(msg)
             # Session is dead, clean it up
             await self._cleanup_session(context_id)
@@ -618,49 +627,6 @@ class MCPStdioClient:
         session_manager = self._get_session_manager()
         return await session_manager.get_session(self._session_context, self._connection_params, "stdio")
 
-    async def _create_fresh_session(self) -> ClientSession:
-        """Create a fresh session using the async context manager pattern."""
-        from mcp.client.stdio import stdio_client
-
-        # This creates a temporary session that will be closed when the context exits
-        # We need to use this within an async context
-        stdio_ctx = stdio_client(self._connection_params)
-        read, write = await stdio_ctx.__aenter__()
-        session = ClientSession(read, write)
-        await session.__aenter__()
-        await session.initialize()
-
-        # Store the context managers so they can be cleaned up later
-        session._stdio_ctx = stdio_ctx
-        session._stdio_read = read
-        session._stdio_write = write
-
-        return session
-
-    async def _cleanup_session(self, session: ClientSession):
-        """Clean up a session and its associated resources."""
-        try:
-            await session.__aexit__(None, None, None)
-        except Exception as e:  # noqa: BLE001
-            logger.info(f"issue cleaning up mcp session: {e}")
-        try:
-            if hasattr(session, "_stdio_ctx"):
-                await session._stdio_ctx.__aexit__(None, None, None)
-        except Exception as e:  # noqa: BLE001
-            logger.info(f"issue cleaning up mcp session: {e}")
-
-    async def disconnect(self):
-        """Properly close the connection and clean up resources."""
-        # Clean up session using session manager
-        if self._session_context:
-            session_manager = self._get_session_manager()
-            await session_manager._cleanup_session(self._session_context)
-
-        self.session = None
-        self._connection_params = None
-        self._connected = False
-        self._session_context = None
-
     async def run_tool(self, tool_name: str, arguments: dict[str, Any]) -> Any:
         """Run a tool with the given arguments using context-specific session.