fix: prevent database connection leaks in chatflow mode by using Session-managed queries (#24656)

Co-authored-by: 王锶奇 <wangsiqi2@tal.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

api/core/app/apps/advanced_chat/app_generator.py

@@ -450,6 +450,12 @@ class AdvancedChatAppGenerator(MessageBasedAppGenerator):
 
         worker_thread.start()
 
+        # release database connection, because the following new thread operations may take a long time
+        db.session.refresh(workflow)
+        db.session.refresh(message)
+        db.session.refresh(user)
+        db.session.close()
+
         # return response or stream generator
         response = self._handle_advanced_chat_response(
             application_generate_entity=application_generate_entity,

api/core/app/apps/advanced_chat/app_runner.py

@@ -72,7 +72,8 @@ class AdvancedChatAppRunner(WorkflowBasedAppRunner):
         app_config = self.application_generate_entity.app_config
         app_config = cast(AdvancedChatAppConfig, app_config)
 
-        app_record = db.session.query(App).where(App.id == app_config.app_id).first()
+        with Session(db.engine, expire_on_commit=False) as session:
+            app_record = session.scalar(select(App).where(App.id == app_config.app_id))
         if not app_record:
             raise ValueError("App not found")