X2.5 时不时出现 Discuz Database Error (2002) notconnect 是怎么回事？

Discuz! Database Error(2002) notconnect
PHP Debug

No.	File	Line	Code
1	home.php	24	discuz_application->init()
2	source/class/discuz/discuz_application.php	65	discuz_application->_init_db()
3	source/class/discuz/discuz_application.php	373	discuz_database::init(%s, Array)
4	source/class/discuz/discuz_database.php	23	db_driver_mysql->connect()
5	source/class/db/db_driver_mysql.php	74	db_driver_mysql->_dbconnect(%s, %s, %s, %s, %s, %s)
6	source/class/db/db_driver_mysql.php	87	db_driver_mysql->halt(%s, %d)
7	source/class/db/db_driver_mysql.php	218	break()