`flush` fails when initilized from object - flask-sqlalchemy

Question

I'm currently running into a permanent while using the flush (or commit as it depends on it) method from SQLAlchemy session under Flask Alchemy
The flush part always failed with sqlalchemy.exc.ResourceClosedError: This transaction is closed (full stack error bellow). While running directly an insert call from engine works as well as retrieving data using the query builder.
Also, deleting an item is working correctly (through session.delete(model) and session.commit())
Here is the code failing:
roles_put = Blueprint('roles_put', __name__)
#roles_put.route('<role_id>', methods=['PUT'])
def role_update(role_id):
role = Role.query.get(role_id)
if not role:
role = Role.query.filter_by(name=role_id).first()
if not role:
raise IDNotFoundError()
print(role)
role.set_data(
request.form,
[
'name', 'manage_user', 'manage_video', 'manage_comment', 'manage_avatar', 'manage_channel', 'manage_reward',
'manage_role', 'manage_top', 'manage_calendar', 'manage_setting', 'validate_video', 'moderate_comment',
]
)
MainAPI.db.session.add(role)
MainAPI.db.session.flush()
MainAPI.db.session.commit()
# if not role.save():
# raise UpdateError()
return jsonify(role.serialize())
SQLAlchemy initialize through:
app = Flask('Name')
def init_db(app, config):
"""
Init SQLAlchemy DB
"""
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql://%s:%s#%s/%s' % (
config.get('database', 'user'),
config.get('database', 'password'),
config.get('database', 'host'),
config.get('database', 'database')
)
print(app.config['SQLALCHEMY_DATABASE_URI'])
MainApi.db = SQLAlchemy(app)
Role Model:
class RoleModel(MainApi.db.Model):
__tablename__ = 'roles'
LOCKED_ROLE_NAMES = ['guest', 'admin', 'logged', 'public']
id = MainApi.db.Column(MainApi.db.Integer, primary_key=True, unique=True, autoincrement=True)
name = MainApi.db.Column(MainApi.db.String(40), nullable=False, unique=True)
# manage rights
manage_user = MainApi.db.Column(MainApi.db.Boolean, nullable=False, default=False)
moderate_comment = MainApi.db.Column(MainApi.db.Boolean, nullable=False, default=False)
created_at = MainApi.db.Column(MainApi.db.DateTime, nullable=False, default=datetime.utcnow)
last_updated_at = MainApi.db.Column(MainApi.db.DateTime, nullable=True)
created_by = MainApi.db.Column(
MainApi.db.Integer,
MainApi.db.ForeignKey(
'users.id', ondelete='RESTRICT', onupdate='CASCADE'
),
nullable=True
)
last_updated_by = MainApi.db.Column(
MainApi.db.Integer,
MainApi.db.ForeignKey(
'users.id', ondelete='CASCADE', onupdate='CASCADE'
), nullable=True
)
users = MainApi.db.relationship(
'UserModel', foreign_keys='UserModel.role_id',
back_populates='role'
)
#staticmethod
def is_allowed(action, role):
"""
Check if user having role can make action
:param action: action name
:type action: str
:param role: user role
:type role: int|str|RoleModel
:return:
"""
if isinstance(role, str):
role = RoleModel.query.filter_by(name=role).first()
elif isinstance(role, int):
role = RoleModel.query.get(role)
if not isinstance(role, RoleModel):
raise Exception
return getattr(role, action.strip().replace(' ', '_'))
#staticmethod
def get_role_id(role):
"""
Check if user having role can make action
:param role: user role
:type role: int|str|RoleModel
:return: role id
:rtype: int
"""
if isinstance(role, str):
role = RoleModel.query.filter_by(name=role).first()
elif isinstance(role, int):
role = RoleModel.query.get(role)
if not isinstance(role, RoleModel):
raise Exception
return role.id
def serialize(self):
users = [u.serialize() for u in self.users] if self.users else []
return {
'id': self.id,
'name': self.name,
'manage_user': self.manage_user,
'moderate_comment': self.moderate_comment,
'created_at': self.created_at,
'last_updated_at': self.last_updated_at,
'created_by': self.created_by,
'last_updated_by': self.last_updated_by,
'users': users,
}
#event.listens_for(RoleModel.name, 'set', propagate=True)
def before_set_name(_target, value, old, _initiator):
print(_initiator)
print(request.url)
if request and 'roles/init' not in request.url:
if old in RoleModel.LOCKED_ROLE_NAMES or value in RoleModel.LOCKED_ROLE_NAMES:
raise UnauthorizedError()
#event.listens_for(RoleModel, 'before_insert', propagate=True)
def receive_before_insert(_mapper, _connection, target):
user = Registry.registered('current-user-id')
target.created_at = datetime.utcnow()
if user:
target.created_by = user
#event.listens_for(RoleModel, 'before_update', propagate=True)
def receive_before_update(_mapper, _connection, target):
user = Registry.registered('current-user-id')
target.updated_at = datetime.utcnow()
if user:
target.updated_by = user
Full error stack:
INFO:werkzeug: * Running on http://localhost:8080/ (Press CTRL+C to quit)
<RoleModel 5>
<sqlalchemy.orm.attributes.Event object at 0x7f5baedf8788>
http://localhost:8080/MainApi/roles/5
ERROR:flask.app:Exception on /MainApi/roles/5 [PUT]
Traceback (most recent call last):
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/sqlalchemy/engine/base.py", line 1177, in _execute_context
conn = self._revalidate_connection()
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/sqlalchemy/engine/base.py", line 469, in _revalidate_connection
raise exc.ResourceClosedError("This Connection is closed")
sqlalchemy.exc.ResourceClosedError: This Connection is closed
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/sqlalchemy/orm/session.py", line 2556, in _flush
flush_context.execute()
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/sqlalchemy/orm/unitofwork.py", line 422, in execute
rec.execute(self)
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/sqlalchemy/orm/unitofwork.py", line 589, in execute
uow,
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/sqlalchemy/orm/persistence.py", line 236, in save_obj
update,
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/sqlalchemy/orm/persistence.py", line 978, in _emit_update_statements
statement, multiparams
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/sqlalchemy/engine/base.py", line 988, in execute
return meth(self, multiparams, params)
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/sqlalchemy/sql/elements.py", line 287, in _execute_on_connection
return connection._execute_clauseelement(self, multiparams, params)
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/sqlalchemy/engine/base.py", line 1107, in _execute_clauseelement
distilled_params,
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/sqlalchemy/engine/base.py", line 1182, in _execute_context
e, util.text_type(statement), parameters, None, None
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/sqlalchemy/engine/base.py", line 1466, in _handle_dbapi_exception
util.raise_from_cause(sqlalchemy_exception, exc_info)
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/sqlalchemy/util/compat.py", line 383, in raise_from_cause
reraise(type(exception), exception, tb=exc_tb, cause=cause)
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/sqlalchemy/util/compat.py", line 128, in reraise
raise value.with_traceback(tb)
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/sqlalchemy/engine/base.py", line 1177, in _execute_context
conn = self._revalidate_connection()
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/sqlalchemy/engine/base.py", line 469, in _revalidate_connection
raise exc.ResourceClosedError("This Connection is closed")
sqlalchemy.exc.StatementError: (sqlalchemy.exc.ResourceClosedError) This Connection is closed
[SQL: UPDATE roles SET name=%s, manage_video=%s WHERE roles.id = %s]
[parameters: [{'name': 'admin2', 'manage_video': '0', 'roles_id': 5}]]
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/flask/app.py", line 2311, in wsgi_app
response = self.full_dispatch_request()
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/flask/app.py", line 1834, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/flask_cors/extension.py", line 161, in wrapped_function
return cors_after_request(app.make_response(f(*args, **kwargs)))
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/flask/app.py", line 1737, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/flask/_compat.py", line 36, in reraise
raise value
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/flask/app.py", line 1832, in full_dispatch_request
rv = self.dispatch_request()
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/flask/app.py", line 1818, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
File "/home/titouan/main_api/python-api/main_api/routes/roles/put.py", line 28, in role_update
MainApi.db.session.flush()
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/sqlalchemy/orm/scoping.py", line 162, in do
return getattr(self.registry(), name)(*args, **kwargs)
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/sqlalchemy/orm/session.py", line 2458, in flush
self._flush(objects)
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/sqlalchemy/orm/session.py", line 2596, in _flush
transaction.rollback(_capture_exception=True)
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/sqlalchemy/util/langhelpers.py", line 79, in __exit__
compat.reraise(type_, value, traceback)
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/sqlalchemy/util/compat.py", line 129, in reraise
raise value
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/sqlalchemy/orm/session.py", line 2596, in _flush
transaction.rollback(_capture_exception=True)
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/sqlalchemy/orm/session.py", line 509, in rollback
self._assert_active(prepared_ok=True, rollback_ok=True)
File "/home/titouan/main_api/python-api/venv/lib/python3.7/site-packages/sqlalchemy/orm/session.py", line 303, in _assert_active
raise sa_exc.ResourceClosedError(closed_msg)
sqlalchemy.exc.ResourceClosedError: This transaction is closed
Version:
Python 3.7.3 (VENV)
MySQL 8 (docker)
Flask-SQLAlchemy==2.4.0 / Flask-SQLAlchemy==2.3.2 (tried both)
Flask==1.0.3
SQLAlchemy==1.3.4
Thanks to anyone having a hint here.

Answer 1

Finally solved it.
The issue was in the models before_insert and before_update callbacks.
Trying to retrieve the current-user-id from Flask.g seems to have a strange impact on the session. It's certainly linked to the way my Registry class implementation works.