def get_next_id(self):
        try:
            query = {'_id': 'last_id'}
            update = {'$inc': {'id': 1}}
            fn = self.db.internal.find_and_modify
            row = fn(query, update, upsert=True, new=True)
        except Exception as e:
            raise DatabaseException(e)
        return row['id']
def __init__(self):
                self.stride = (4, 8, 16, 32, 64)
                self.short = (200, 100, 50, 25, 13)
                self.long = (334, 167, 84, 42, 21)