Hello,
i would like to ask if is this correct approach in multi-threaded
application:
Base = declarative_base()
engine = create_engine("sqlite:///datafiles/data.sqlite",
connect_args={'check_same_thread': False})
Base.metadata.create_all(engine)
Session = scoped_session(sessionmaker(bind=engine))
# Session = sessionmaker(bind=engine)
ses = Session()
class Table1(Base):
__tablename__ = 'table1'
id = Column(Integer, primary_key=True)
name = Column(String)
def print(self):
print('\n',self.__class__)
print('session factory:', Session)
session = Session()
print('thread local session:', session)
session.query(Table1)
print('sa_instance session:', self._sa_instance_state.session)
# Base.metadata.drop_all(d.engine)
Base.metadata.create_all(engine)
t1 = ses.query(Table1).all()[0]
t1.print()
threading.Thread(target=t1.print).start()
i see issue that queried Table1 instance t1 contains 'main thread'
threadlocal session reference - t1._sa_instance_state.session.
output:
Main thread:
<class '__main__.Table1'>
session factory: <sqlalchemy.orm.scoping.scoped_session object at
0x00000000038275C0>
thread local session: <sqlalchemy.orm.session.Session object at
0x0000000003827320>
*sa_instance session: <sqlalchemy.orm.session.Session object at
0x0000000003827320>*
Spawned thread:
<class '__main__.Table1'>
session factory: <sqlalchemy.orm.scoping.scoped_session object at
0x00000000038275C0>
thread local session: <sqlalchemy.orm.session.Session object at
0x0000000003827438>
*sa_instance session: <sqlalchemy.orm.session.Session object at
0x0000000003827320>*
Process finished with exit code 0
Beacuse of threads will spawn another threads and data are always handled
by one thread - specific thread is initialized by specific table row and
based on data will initialize rows in different table and spawn respective
threads, it sounds to me as most suitable approach.
So my question is - do you think this is acceptable design approach? If no
do you have any suggestions?
Will t1._sa_instance_state.session cause issues? If yes can be replaced by
current threadlocal session? Or is there different technique how to pass
ORM intances to threads?
Thanks
Jan
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