Cloud SQL connection with SQL Alchemy not working

Question

It is impossible to connect an app in Flask / App Engine to Google Cloud MySQL.

The settings seems correct.

Here are the libraries:

python 38

Flask-SQLAlchemy==2.5.1

pymysql==1.0.2

Here is the mydatabase.py:

unix_socket = "/cloudsql/{conn_name}".format(conn_name=DBCONNECTION)
SQLALCHEMY_DATABASE_URI = ("mysql+pymysql://{user}:{password}@/{database}?unix_socket={socket}").format(user=USER, password=PWD,database=SQLDB, socket=unix_socket)
    
    
db = SQLAlchemy()

Here is the main.py:

from mydatabase import db,SQLALCHEMY_DATABASE_URI

db.init_app(app)

The error is strange, it seems that the driver isn't working correctly:

"POST /signin HTTP/1.1" 500
2022-12-06 14:41:34 default[2022120025]  [2022-12-06 14:41:34,165] ERROR in app: Exception on /signin [POST]
2022-12-06 14:41:34 default[2022120025]  Traceback (most recent call last):    File "/layers/google.python.pip/pip/lib/python3.8/site-packages/pymysql/connections.py", line 602, in connect      sock.connect(self.unix_socket)  ConnectionRefusedError: [Errno 111] Connection refused
2022-12-06 14:41:34 default[2022120025]  During handling of the above exception, another exception occurred:
2022-12-06 14:41:34 default[2022120025]  Traceback (most recent call last):    File "/layers/google.python.pip/pip/lib/python3.8/site-packages/sqlalchemy/engine/base.py", line 3361, in _wrap_pool_connect      return fn()    File "/layers/google.python.pip/pip/lib/python3.8/site-packages/sqlalchemy/pool/base.py", line 325, in connect      return _ConnectionFairy._checkout(self)    File "/layers/google.python.pip/pip/lib/python3.8/site-packages/sqlalchemy/pool/base.py", line 888, in _checkout      fairy = _ConnectionRecord.checkout(pool)    File "/layers/google.python.pip/pip/lib/python3.8/site-packages/sqlalchemy/pool/base.py", line 491, in checkout      rec = pool._do_get()    File "/layers/google.python.pip/pip/lib/python3.8/site-packages/sqlalchemy/pool/impl.py", line 146, in _do_get      self._dec_overflow()    File "/layers/google.python.pip/pip/lib/python3.8/site-packages/sqlalchemy/util/langhelpers.py", line 70, in __exit__      compat.raise_(    File "/layers/google.python.pip/pip/lib/python3.8/site-packages/sqlalchemy/util/compat.py", line 210, in raise_      raise exception    File "/layers/google.python.pip/pip/lib/python3.8/site-packages/sqlalchemy/pool/impl.py", line 143, in _do_get      return self._create_connection()    File "/layers/google.python.pip/pip/lib/python3.8/site-packages/sqlalchemy/pool/base.py", line 271, in _create_connection      return _ConnectionRecord(self)    File "/layers/google.python.pip/pip/lib/python3.8/site-packages/sqlalchemy/pool/base.py", line 386, in __init__      self.__connect()    File "/layers/google.python.pip/pip/lib/python3.8/site-packages/sqlalchemy/pool/base.py", line 685, in __connect      pool.logger.debug("Error on connect(): %s", e)    File "/layers/google.python.pip/pip/lib/python3.8/site-packages/sqlalchemy/util/langhelpers.py", line 70, in __exit__      compat.raise_(    File "/layers/google.python.pip/pip/lib/python3.8/site-packages/sqlalchemy/util/compat.py", line 210, in raise_      raise exception    File "/layers/google.python.pip/pip/lib/python3.8/site-packages/sqlalchemy/pool/base.py", line 680, in __connect      self.dbapi_connection = connection = pool._invoke_creator(self)    File "/layers/google.python.pip/pip/lib/python3.8/site-packages/sqlalchemy/engine/create.py", line 578, in connect      return dialect.connect(*cargs, **cparams)    File "/layers/google.python.pip/pip/lib/python3.8/site-packages/sqlalchemy/engine/default.py", line 598, in connect      return self.dbapi.connect(*cargs, **cparams)    File "/layers/google.python.pip/pip/lib/python3.8/site-packages/pymysql/connections.py", line 353, in __init__      self.connect()    File "/layers/google.python.pip/pip/lib/python3.8/site-packages/pymysql/connections.py", line 664, in connect      raise exc  pymysql.err.OperationalError: (2003, "Can't connect to MySQL server on 'localhost' ([Errno 111] Connection refused)")

I've added additional Cloud SQL admin rights to the Compute Engine default service account and the App Engine default service account, but it doesn't solve the problem.

I've also tried to use the method with the public IP adding the IP into the the authorized list using curl api.ipify.org, but it doesn't work.

Answer 1

In fact, there was initially some rights and install issue, so I've checked a function and installed again the main components.

I've solved the issue by using the shell command gcloud sql instances describe instance_name that activates some admin rights and installing gcloud components install app-engine-python that probably install everything correctly.