class Model(db.Model):
    name = db.Column(db.String(255), index=True, unique=True)
    active = db.Column(db.Boolean)

    def create(self):
        db.session.add(self)
        db.session.commit()

    def update(self):
        db.session.commit()


def run_update():
    while True:

        models = Model.query.filter_by(active=True).all()
        for model in models:
            do_something(model)
            time.sleep(300)

def do_something():
    longtask = threading.Thread(target=long_task)
    longtask.start()


def long_task():
    // Update database here again
    // Task has finished before it is run again.
    time.sleep(10)