Django rest framework 默认值随机标识符

Question

当我尝试在 MongoEngine 中保存 DynamicDocument 时，我试图调试一个奇怪的行为。文档class声明如下：

class Command(DynamicDocument):
    meta = {
        'collection': 'executor_data_commands'
    }

    name = StringField()
    args = DynamicField()
    issued_at = LongField(default=time.time())
    sync_with_kafka = BooleanField(default=False)
    correlation_id = StringField(
        default=''.join(random.choice(string.ascii_uppercase + string.digits) for _ in range(10))
    )
    commands_output = DynamicField(default=None)

    @classmethod
    def post_save(cls, sender, document, **kwargs):
        """
        Send data to Kafka executor data topic after a new instance has been saved
        :param sender: the sender who emitted the signal
        :param document: the saved instance
        """
        if kwargs['created']:
            CommandHandler(document).send_command()



class CommandHandler:
    """
    Command handler class
    """

    def __init__(self, command_instance):
        self.command_instance = command_instance

    def send_command(self):
        """
        Send command to Kafka queue and save the response in the
        local database
        :return: True if message is published over Kafka channel
        False otherwise
        """
        headers = {
            "Content-Type": "application/vnd.kafka.json.v2+json",
            "Accept": "application/vnd.kafka.v2+json"
        }

        logger_kafka_handlers.info(
            "Got new command: %s - %s" % (self.command_instance.name, self.command_instance.args))

        args = self.command_instance.args
        if 'machine_identifier' in args:
            args['machine_identifier'] = MACHINE_MAPPING.get(args['machine_identifier'], args['machine_identifier'])

        response = requests.post(
            KAFKA_BROKER_EXECUTOR_COMMANDS_IN['host'],
            json={"records": [{"value": {
                "name": self.command_instance.name,
                "args": args,
                "correlation_id": self.command_instance.correlation_id,
                "issued_ts": time.time()
            }}]},
            headers=headers,
            auth=(KAFKA_BROKER_EXECUTOR_COMMANDS_IN['user'], KAFKA_BROKER_EXECUTOR_COMMANDS_IN['password'])

        )

        self.command_instance.sync_with_kafka = True if response.status_code == 200 else False
        self.command_instance.save()
        logger_kafka_handlers.info(
        "Handled new command; Name: %s - Args: %s - Sync with Kafka: %s; CorrelationId: %s" % (
            self.command_instance.name, self.command_instance.args, self.command_instance.sync_with_kafka,
            self.command_instance.correlation_id))

所以我希望创建的文档将有 10 个随机字母 correlation_id 并传递给 post_save 基本上执行 HTTP 请求并记录实例字段的处理程序。

问题与 correlation_id 字段相关：似乎分配给每个保存实例的默认值等于数据库中保存的另一个实例。

我排除了幕后更新查询以及一些变量重新分配，因为在 send_command[=27= 的最后一行记录实例字段时，问题很明显] 方法。

想法？

谢谢， FB

Answer 1

问题在于您对 default 值的理解。

我不确定 mongo DynamicDocument，但我认为它的行为与普通模型相同。

所以，来自文档：

The default value for the field. This can be a value or a callable object. If callable it will be called every time a new object is created.

在您的情况下，它是不可调用的，因此在创建模型 class 时仅调用一次。

您需要使其可调用，因此将实现移至函数：

def generate_random_corr():
    return ''.join(random.choice(string.ascii_uppercase + string.digits) for _ in range(10))

并在模型 class 中使用它，如下所示：

 correlation_id = StringField(default=generate_random_corr)

同样适用于其他领域：

issued_at = LongField(default=time.time())

所有对象的时间都相同。

Django rest framework 默认值随机标识符

Django rest framework default value random identifier

django

mongoengine

django-rest-framework