在应用程序上下文中运行Celery worker仍会在任务中引发"在app context之外工作"错误

Question

我正在使用Miguel Grinberg的文章使用应用工厂模式设置Celery,以便使用Flask-Mail发送电子邮件.我一直在调用使用Celery的各种脚本而没有任何问题.但是Runtime Error: working outside of application context,即使我在应用程序上下文中运行worker,我也会继续执行以下任务.为什么我收到此错误？如何让Flask-Mail在Celery中运行？

email.py:

from flask import current_app, render_template
from flask.ext.mail import Message
from . import celery, mail

@celery.task
def send_async_email(msg):
    mail.send(msg)

def send_email(to, subject, template, **kwargs):
    with current_app.test_request_context(): # used app_context() as well.
        msg = Message(current_app.config['PORTAL_MAIL_SUBJECT_PREFIX'] + ' ' +                                       subject,
                  sender=current_app.config['PORTAL_MAIL_SENDER'], recipients=[to])
        msg.body = render_template(template + '.txt', **kwargs)
        msg.html = render_template(template + '.html', **kwargs)
        send_async_email.delay(msg)

__init__.py:

from flask import Flask
from celery import Celery
from flask.ext.mail import Mail
from configuration import config

mail = Mail()
celery = Celery(__name__, broker=config['default'].CELERY_BROKER_URL)

def create_app(config_name):
    app = Flask(__name__)
    app.config.from_object(config[config_name])
    config[config_name].init_app(app)
    mail.init_app(app)
    celery.conf.update(app.config)
    app.register_blueprint(main_blueprint)
    return app

celery_worker.py:

import os
from app import celery, create_app

app = create_app(os.getenv('FLASK_CONFIG') or 'default')
app.app_context().push()

错误:

C:\Python27\Scripts\celery.exe worker -A celery_worker.celery --loglevel=info

[2015-09-30 12:07:34,408: INFO/MainProcess] Received task: app.email.send_async_email[3ec772ff-4767-49cb-90ba-445629da30da]
[2015-09-30 12:07:34,417: ERROR/MainProcess] Task app.email.send_async_email[3ec772ff-4767-49cb-90ba-445629da30da] raised unexpected: RuntimeError('working outside of application context',)
Traceback (most recent call last):
  File "C:\Python27\lib\site-packages\celery\app\trace.py", line 240, in trace_task
    R = retval = fun(*args, **kwargs)
  File "C:\Python27\lib\site-packages\celery\app\trace.py", line 438, in __protected_call__
    return self.run(*args, **kwargs)
  File "<flask_project_path>\app\email.py", line 10, in send_async_email
    mail.send(msg)
  File "C:\Python27\lib\site-packages\flask_mail.py", line 491, in send
    with self.connect() as connection:
  File "C:\Python27\lib\site-packages\flask_mail.py", line 508, in connect
    return Connection(app.extensions['mail'])
  File "C:\Python27\lib\site-packages\werkzeug\local.py", line 338, in __getattr__
    return getattr(self._get_current_object(), name)
  File "C:\Python27\lib\site-packages\werkzeug\local.py", line 297, in _get_current_object
    return self.__local()
  File "C:\Python27\lib\site-packages\flask\globals.py", line 34, in _find_app
    raise RuntimeError('working outside of application context')
RuntimeError: working outside of application context

我试过了:

• 尝试将应用程序上下文传递给send_email方法.
• 将send_async_email方法移动到其余celery任务所在的tasks.py模块.
• 在电子邮件方法之外呈现模板并将它们作为参数传递.

Answer 1

我能够通过在本地创建 Flask 应用程序的实例来解决该问题：

email.py:

from flask import render_template, current_app
from flask.ext.mail import Message
from . import celery, mail, create_app


@celery.task
def send_async_email(msg):
    app = create_app('default' or 'development')  # -> fixed
    with app.app_context():
        mail.send(msg)


def send_email(to, subject, template, **kwargs):
    app = current_app._get_current_object()
    msg = Message(current_app.config['PORTAL_MAIL_SUBJECT_PREFIX'] + ' ' +     subject,
    sender=current_app.config['MAIL_USERNAME'], recipients=[to])
    msg.body = render_template(template + '.txt', **kwargs)
    msg.html = render_template(template + '.html', **kwargs)
    send_async_email.delay(msg)