使用Django，celery和Redis安排任務

Question

我在Celery中添加了一個任務，用於數據導出。 我希望當用戶調用Export all按鈕時， Export all任務開始，並且在前端繼續進行Export all的同時，前端顯示django消息 。 但是根據我的能力，我在views.py有這個：

def CasesPaluExport(request):
    export_cases_palu.delay(request=request)
    messages.success(request, 'CasesPaluExport')
    return JsonResponse({"Ok": "ok"}, safe=False)

這在tasks.py ：

def export_cases_palu(request):
    try:
        plaintext = get_template('stock/download_case_palu.txt')
        htmly = get_template('stock/download_case_palu.html')
        d = Context({'username': request.user.username})

        subject, from_email, to = 'Download all cases palu', settings.DEFAULT_FROM_EMAIL, request.user.email
        text_content = plaintext.render(d)
        html_content = htmly.render(d)
        msg = EmailMultiAlternatives(subject, text_content, from_email, [to])
        msg.attach_alternative(html_content, "text/html")
        msg.send()
    except:
        logging.warning("Tried to send download email to user {0}".format(request.user))

問題是，每當我調用CasesPaluExport函數時，都會在export_cases_palu.delay(request=request)行出現錯誤：

Internal Server Error: /user/casepaluexport/
Traceback (most recent call last):
  File "/home/user/.virtualenvs/project/local/lib/python2.7/site-packages/django/core/handlers/exception.py", line 41, in inner
    response = get_response(request)
  File "/home/user/.virtualenvs/project/local/lib/python2.7/site-packages/django/core/handlers/base.py", line 187, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "/home/user/.virtualenvs/project/local/lib/python2.7/site-packages/django/core/handlers/base.py", line 185, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/user/.virtualenvs/project/local/lib/python2.7/site-packages/django/views/decorators/csrf.py", line 58, in wrapped_view
    return view_func(*args, **kwargs)
  File "/home/user/project/user/views.py", line 170, in CasesPaluExport
    export_cases_palu.delay(request=request)
  File "/home/user/.virtualenvs/project/local/lib/python2.7/site-packages/celery/app/task.py", line 413, in delay
    return self.apply_async(args, kwargs)
  File "/home/user/.virtualenvs/project/local/lib/python2.7/site-packages/celery/app/task.py", line 536, in apply_async
    **options
  File "/home/user/.virtualenvs/project/local/lib/python2.7/site-packages/celery/app/base.py", line 737, in send_task
    amqp.send_task_message(P, name, message, **options)
  File "/home/user/.virtualenvs/project/local/lib/python2.7/site-packages/celery/app/amqp.py", line 554, in send_task_message
    **properties
  File "/home/user/.virtualenvs/project/local/lib/python2.7/site-packages/kombu/messaging.py", line 169, in publish
    compression, headers)
  File "/home/user/.virtualenvs/project/local/lib/python2.7/site-packages/kombu/messaging.py", line 252, in _prepare
    body) = dumps(body, serializer=serializer)
  File "/home/user/.virtualenvs/project/local/lib/python2.7/site-packages/kombu/serialization.py", line 221, in dumps
    payload = encoder(data)
  File "/usr/lib/python2.7/contextlib.py", line 35, in __exit__
    self.gen.throw(type, value, traceback)
  File "/home/user/.virtualenvs/project/local/lib/python2.7/site-packages/kombu/serialization.py", line 54, in _reraise_errors
    reraise(wrapper, wrapper(exc), sys.exc_info()[2])
  File "/home/user/.virtualenvs/project/local/lib/python2.7/site-packages/kombu/serialization.py", line 50, in _reraise_errors
    yield
  File "/home/user/.virtualenvs/project/local/lib/python2.7/site-packages/kombu/serialization.py", line 221, in dumps
    payload = encoder(data)
  File "/home/user/.virtualenvs/project/local/lib/python2.7/site-packages/kombu/utils/json.py", line 72, in dumps
    **dict(default_kwargs, **kwargs))
  File "/usr/lib/python2.7/json/__init__.py", line 250, in dumps
    sort_keys=sort_keys, **kw).encode(obj)
  File "/usr/lib/python2.7/json/encoder.py", line 207, in encode
    chunks = self.iterencode(o, _one_shot=True)
  File "/usr/lib/python2.7/json/encoder.py", line 270, in iterencode
    return _iterencode(o, 0)
  File "/home/user/.virtualenvs/project/local/lib/python2.7/site-packages/kombu/utils/json.py", line 62, in default
    return super(JSONEncoder, self).default(o)
  File "/usr/lib/python2.7/json/encoder.py", line 184, in default
    raise TypeError(repr(o) + " is not JSON serializable")
EncodeError: <WSGIRequest: POST '/user/casepaluexport/'> is not JSON serializable
[20/Nov/2017 15:47:56] "POST /user/casepaluexport/ HTTP/1.1" 500 186320

這可能表明服務器仍在等待http響應。 我該如何解決？

Answer 1

錯誤告訴您無法序列化整個request以將其發送到任務。

但是，您在請求中僅在任務本身中使用的是用戶對象。 您應該只發送用戶ID，並在任務中獲取對象本身。

 export_cases_palu.delay(user_id=request.user.id)

...

def export_cases_palu(user_id):
    user = User.objects.get(id=user_id)
    d = Context({'username': user.username})

（此外，您不應將整個任務包裝在try / except中。）

Answer 2

第一件事：每次添加或刪除任何芹菜方法時，都必須重新啟動芹菜
第二件事：celery內部將方法參數以JSON對象格式存儲在數據庫中的celery內部存儲（堆棧）方法，因此您只能在那里傳遞JSON可序列化的對象，而請求不能JSON序列化