"Can't connect to MySQL server on 'localhost' ([Errno 111] Connection refused)")

[Dmitry Margolin]

My application is running.

I can run it and connect locally when point to ip on CloudSql

SQLALCHEMY_DATABASE_URI = "mysql+pymysql://{}:{}@{}/{}".format(db_user,db_pass,db_host,db_name)

When I change it and run it on server:

SQLALCHEMY_DATABASE_URI = "mysql+pymysql:///unix_socket=/{}/{}".format(db_user,db_pass,db_name,db_socket_dir,cloud_sql_connection_name)

I got:

sqlalchemy.exc.OperationalError: (pymysql.err.OperationalError) (2003, "Can't connect to MySQL server on 'localhost' ([Errno 111] Connection refused)")

[wokmou]

Looking at some public forums [1][2] , I found some valid reasons why you may experiencing this error.  Mostly related to your MySQL server only listening the localhost interface or db user’s privileges. 

[1]https://stackoverflow.com/a/1420862/7046224

[2]https://discuss.erpnext.com/t/cant-connect-to-mysql-server-on-u-local-host-error-111-connection-refused/41047/2