celery —— 任務調用方式

實際上 delay 只是 apply_async 的快捷方式，二者作用相同，只是 apply_async 可以進行更多的任務屬性設置，比如 callbacks/errbacks 正常回調與錯誤回調、執行超時、重試、重試時間等等

celery\app\task.py 中的Task類下的delay方法

class Task(object):

    def delay(self, *args, **kwargs):
        """Star argument version of :meth:`apply_async`.

        Does not support the extra options enabled by :meth:`apply_async`.
    
        Arguments:
            *args (Any): Positional arguments passed on to the task.
            **kwargs (Any): Keyword arguments passed on to the task.
        eturns:
            celery.result.AsyncResult: Future promise.
        """
        return self.apply_async(args, kwargs)

def apply_async(self, args=None, kwargs=None, task_id=None, producer=None,
 link=None, link_error=None, shadow=None, **options):
......

return app.send_task(
    self.name, args, kwargs, task_id=task_id, producer=producer,
 link=link, link_error=link_error, result_cls=self.AsyncResult,
 shadow=shadow, task_type=self,
 **options
)

def send_task(self, name, args=None, kwargs=None, countdown=None,
 eta=None, task_id=None, producer=None, connection=None,
 router=None, result_cls=None, expires=None,
 publisher=None, link=None, link_error=None,
 add_to_parent=True, group_id=None, retries=0, chord=None,
 reply_to=None, time_limit=None, soft_time_limit=None,
 root_id=None, parent_id=None, route_name=None,
 shadow=None, chain=None, task_type=None, **options):

......

result = (result_cls or self.AsyncResult)(task_id)
......

return result

delay 返回的是一個 AsyncResult 對象，里面存的就是一個異步的結果，當任務完成時result.ready() 為 true，然后用 result.get() 取結果即可。

#官方文檔
apply_async() and Task.delay() will return an EagerResult instance, that emulates the API and behavior of AsyncResult, except the result is already evaluated.