refactor: recycle db connection to avoid "the connection is closed" exception. (#3726) (#3727)

Author: shaohuzhang1

apps/smartdoc/conf.py

@@ -113,6 +113,7 @@ def get_db_setting(self) -> dict:
             "USER": self.get('DB_USER'),
             "PASSWORD": self.get('DB_PASSWORD'),
             "ENGINE": self.get('DB_ENGINE'),
+            "CONN_MAX_AGE": 0,
             "POOL_OPTIONS": {
                 "POOL_SIZE": 20,
                 "MAX_OVERFLOW": int(self.get('DB_MAX_OVERFLOW')),