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

 
         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

         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")
 

api/core/app/apps/message_based_app_generator.py

 from collections.abc import Generator
 from typing import Optional, Union, cast
 
+from sqlalchemy import select
+from sqlalchemy.orm import Session
+
 from core.app.app_config.entities import EasyUIBasedAppConfig, EasyUIBasedAppModelConfigFrom
 from core.app.apps.base_app_generator import BaseAppGenerator
 from core.app.apps.base_app_queue_manager import AppQueueManager
         :param conversation_id: conversation id
         :return: conversation
         """
-        conversation = db.session.query(Conversation).where(Conversation.id == conversation_id).first()
+        with Session(db.engine, expire_on_commit=False) as session:
+            conversation = session.scalar(select(Conversation).where(Conversation.id == conversation_id))
 
         if not conversation:
             raise ConversationNotExistsError("Conversation not exists")
         :param message_id: message id
         :return: message
         """
-        message = db.session.query(Message).where(Message.id == message_id).first()
+        with Session(db.engine, expire_on_commit=False) as session:
+            message = session.scalar(select(Message).where(Message.id == message_id))
 
         if message is None:
             raise MessageNotExistsError("Message not exists")

api/core/app/task_pipeline/message_cycle_manager.py

 from typing import Optional, Union
 
 from flask import Flask, current_app
+from sqlalchemy import select
+from sqlalchemy.orm import Session
 
 from configs import dify_config
 from core.app.entities.app_invoke_entities import (
         :param event: event
         :return:
         """
-        message_file = db.session.query(MessageFile).where(MessageFile.id == event.message_file_id).first()
+        with Session(db.engine, expire_on_commit=False) as session:
+            message_file = session.scalar(select(MessageFile).where(MessageFile.id == event.message_file_id))
 
         if message_file and message_file.url is not None:
             # get tool file id
         :param message_id: message id
         :return:
         """
-        message_file = db.session.query(MessageFile).where(MessageFile.id == message_id).first()
+        with Session(db.engine, expire_on_commit=False) as session:
+            message_file = session.scalar(select(MessageFile).where(MessageFile.id == message_id))
         event_type = StreamEvent.MESSAGE_FILE if message_file else StreamEvent.MESSAGE
 
         return MessageStreamResponse(