Connecting to Cloud SQL from Google Cloud Function using Python and SQLAlchemy

I read all documentation related to connecting to MysQL hosted in Cloud SQL from GCF and still can’t connect. Also, tried all hints in documentation of SQLAlchemy related to this. I am using the following connection

con = 'mysql+pymysql://USER:PASSWORD@/MY_DB?unix_socket=/cloudsql/Proj_ID:Zone:MySQL_Instance_ID'
mysqlEngine = sqlalchemy.create_engine(con)

The error I got was:

(pymysql.err.OperationalError) (2003, “Can’t connect to MySQL server on ‘localhost’ ([Errno 111] Connection refused)”) (Background on this error at: http://sqlalche.me/e/e3q8)

Answer

After a long thread with Google Support, we found the reason to be: simply we should enable public access to Cloud SQL without any firewall rule. It is undocumented and can drive you crazy, but the silver bullet for the support team is to say: it is in beta!