如何使用 Celery 在 Django 中发送异步电子邮件？

Question

我正在尝试在 Django 1.6.2 应用程序中使用 django-celery-email 和 Celery 3.1.17 以及 RabbitMQ 3.5.0 作为我的消息代理和结果后端来发送异步电子邮件。正在发送和接收电子邮件，但在发送电子邮件时，我的 Celery 日志中也出现错误“django.core.mail ... is not JSON serializable”。我在 Celery 中使用 JSON 进行序列化，因为 pickle 已被弃用。有什么方法可以更改我的配置以防止发生此错误？顺便说一句，不使用 Celery 的延迟方法时，我可以很好地发送电子邮件。

谢谢。

# Stacktrace
Task app.tasks.send_email with id 7ac1eb8e-c090-4893-8147-1f204e463d12 raised exception:
'EncodeError(TypeError("<module \'django.core.mail\' from \'/Users/me/venv/django/lib/python2.7/site-packages/django/core/mail/__init__.pyc\'> is not JSON serializable",),)'


Task was called with args: [] kwargs: {}.

The contents of the full traceback was:

Traceback (most recent call last):
 File "/Users/me/venv/django/lib/python2.7/site-packages/celery/app/trace.py", line 283, in trace_task
   uuid, retval, SUCCESS, request=task_request,
 File "/Users/me/venv/django/lib/python2.7/site-packages/celery/backends/amqp.py", line 136, in store_result
   delivery_mode=self.delivery_mode,
 File "/Users/me/venv/django/lib/python2.7/site-packages/kombu/messaging.py", line 161, in publish
   compression, headers)
 File "/Users/me/venv/django/lib/python2.7/site-packages/kombu/messaging.py", line 237, in _prepare
   body) = dumps(body, serializer=serializer)
 File "/Users/me/venv/django/lib/python2.7/site-packages/kombu/serialization.py", line 164, in dumps
   payload = encoder(data)
 File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/contextlib.py", line 35, in __exit__
   self.gen.throw(type, value, traceback)
 File "/Users/me/venv/django/lib/python2.7/site-packages/kombu/serialization.py", line 59, in _reraise_errors
   reraise(wrapper, wrapper(exc), sys.exc_info()[2])
 File "/Users/me/venv/django/lib/python2.7/site-packages/kombu/serialization.py", line 55, in _reraise_errors
   yield
 File "/Users/me/venv/django/lib/python2.7/site-packages/kombu/serialization.py", line 164, in dumps
   payload = encoder(data)
 File "/Users/me/venv/django/lib/python2.7/site-packages/anyjson/__init__.py", line 141, in dumps
   return implementation.dumps(value)
 File "/Users/me/venv/django/lib/python2.7/site-packages/anyjson/__init__.py", line 87, in dumps
   return self._encode(data)
 File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/json/__init__.py", line 243, in dumps
   return _default_encoder.encode(obj)
 File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/json/encoder.py", line 207, in encode
   chunks = self.iterencode(o, _one_shot=True)
 File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/json/encoder.py", line 270, in iterencode
   return _iterencode(o, 0)
 File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/json/encoder.py", line 184, in default
   raise TypeError(repr(o) + " is not JSON serializable")
EncodeError: <module 'django.core.mail' from '/Users/me/venv/django/lib/python2.7/site-packages/django/core/mail/__init__.pyc'> is not JSON serializable

# settings.py
# MAIL SETTINGS
EMAIL_HOST = 'smtp.sendgrid.net'
EMAIL_HOST_USER = 'me'
EMAIL_HOST_PASSWORD ='password'
EMAIL_PORT = 587
EMAIL_USE_TLS = True
FAIL_SILENTLY = False

# CELERY SETTINGS
BROKER_URL = 'amqp://guest@localhost//'
CELERY_RESULT_BACKEND = 'amqp'
CELERY_TASK_SERIALIZER = 'json'
CELERY_RESULT_SERIALIZER = 'json'
CELERY_ACCEPT_CONTENT = ['json', ]

# DJANGO-CELERY-EMAIL
INSTALLED_APPS += ('djcelery_email', )
EMAIL_BACKEND = 'djcelery_email.backends.CeleryEmailBackend'

# tasks.py
from __future__ import absolute_import

import smtplib
from conf.celery import app
from django.core import mail
from django.template.loader import render_to_string

@app.task
def send_email():
    to_email = 'me@example.com'
    subject = 'Testing Celery/RabbitMQ'
    from_email = 'me2@example.com'
    message = 'This is a test of my Celery/RabbitMQ function.'
    recipient_list = []
    recipient_list.append(to_email)
    html_message = render_to_string('send_mail.html', {'message': message})
    try:
        mail.send_mail(subject, message, from_email, recipient_list, html_message)
    except smtplib.SMTPException, e:
        return 0
    return mail

# views.py
from app.tasks import send_email
def home_page(request, template):
    # Send mail synchronously
    #send_email()
    # Send email asynchronously.
    send_email.delay()
    return render(request, template)

Answer 1

您收到了预期的错误。 Celery 设置为使用 JSON 序列化，并使用内置的 json 库尝试序列化 django.core.mail，这显然不支持任何形式的序列化。

在没有delay 的情况下调用它的原因是因为它像调用典型函数一样工作（在同一进程中）。

如果您必须从任务中返回某些内容，您可以返回支持序列化的值或对象的字典。对于自定义序列化，您可以使用serializer 属性并在调用任务时传递您的自定义解码器/编码器。

在您的情况下，您可以返回 {'success': True} 之类的内容，并对任何失败返回 False 值。

More options 关于使用自定义序列化程序