now the company has a requirement. When a project starts, it often reports an error because the database is not started, resulting in the project cannot be started. How to make the project start without caring whether MySQL is started or not? to put it simply, when you get the data of MySQL, you can report that MySQL did not start, instead of reporting an error at the beginning. As a result, the project cannot be started because the project is not entirely dependent on MySQL, and MongoDB. Sometimes you don"t need to use MySQL,. Only some data will use MySQL.