Python Flask with celery 脱离了应用程序上下文

Z时代
2024-01-10
分类：问答

我正在使用python Flask建立一个网站。一切进展顺利，现在我正在尝试实施celery。

在我尝试使用celery的flask-mail发送电子邮件之前，这种情况也很好。现在，我收到“在应用程序上下文之外工作”错误。

完整的追溯是

  Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/celery/task/trace.py", line 228, in trace_task
    R = retval = fun(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/celery/task/trace.py", line 415, in __protected_call__
    return self.run(*args, **kwargs)
  File "/home/ryan/www/CG-Website/src/util/mail.py", line 28, in send_forgot_email
    msg = Message("Recover your Crusade Gaming Account")
  File "/usr/lib/python2.7/site-packages/flask_mail.py", line 178, in __init__
    sender = current_app.config.get("DEFAULT_MAIL_SENDER")
  File "/usr/lib/python2.7/site-packages/werkzeug/local.py", line 336, in __getattr__
    return getattr(self._get_current_object(), name)
  File "/usr/lib/python2.7/site-packages/werkzeug/local.py", line 295, in _get_current_object
    return self.__local()
  File "/usr/lib/python2.7/site-packages/flask/globals.py", line 26, in _find_app
    raise RuntimeError('working outside of application context')
RuntimeError: working outside of application context

这是我的邮件功能：

@celery.task
def send_forgot_email(email, ref):
    global mail
    msg = Message("Recover your Crusade Gaming Account")
    msg.recipients = [email]
    msg.sender = "Crusade Gaming stuff@cg.com"
    msg.html = \
        """
        Hello Person,<br/>
        You have requested your password be reset. <a href="{0}" >Click here recover your account</a> or copy and paste this link in to your browser: {0} <br />
        If you did not request that your password be reset, please ignore this.
        """.format(url_for('account.forgot', ref=ref, _external=True))
    mail.send(msg)

这是我的celery文件：

from __future__ import absolute_import
from celery import Celery
celery = Celery('src.tasks',
                broker='amqp://',
                include=['src.util.mail'])
if __name__ == "__main__":
    celery.start()

回答：

这是一个与flask应用程序工厂模式一起使用的解决方案，并且无需使用即可创建具有上下文的celery任务app.app_context()。在避免循环导入的同时获取该应用程序确实很棘手，但这可以解决问题。这是针对celery4.2的，这是撰写本文时的最新版本。

结构体：

repo_name/ manage.py base/ base/__init__.py base/app.py base/runcelery.py base/celeryconfig.py base/utility/celery_util.py base/tasks/workers.py

因此base是主要的应用程序包在这个例子中。在中，base/__init__.py我们创建celery实例，如下所示：

from celery import Celery
celery = Celery('base', config_source='base.celeryconfig')

该base/app.py文件包含flask应用程序工厂，create_app并注意init_celery(app, celery)其中包含：

from base import celery
from base.utility.celery_util import init_celery
def create_app(config_obj):
    """An application factory, as explained here:
    http://flask.pocoo.org/docs/patterns/appfactories/.
    :param config_object: The configuration object to use.
    """
    app = Flask('base')
    app.config.from_object(config_obj)
    init_celery(app, celery=celery)
    register_extensions(app)
    register_blueprints(app)
    register_errorhandlers(app)
    register_app_context_processors(app)
    return app

转到base/runcelery.py内容：

from flask.helpers import get_debug_flag
from base.settings import DevConfig, ProdConfig
from base import celery
from base.app import create_app
from base.utility.celery_util import init_celery
CONFIG = DevConfig if get_debug_flag() else ProdConfig
app = create_app(CONFIG)
init_celery(app, celery)

接下来，base/celeryconfig.py文件（作为示例）：

# -*- coding: utf-8 -*-
"""
Configure Celery. See the configuration guide at ->
http://docs.celeryproject.org/en/master/userguide/configuration.html#configuration
"""
## Broker settings.
broker_url = 'pyamqp://guest:guest@localhost:5672//'
broker_heartbeat=0
# List of modules to import when the Celery worker starts.
imports = ('base.tasks.workers',)
## Using the database to store task state and results.
result_backend = 'rpc'
#result_persistent = False
accept_content = ['json', 'application/text']
result_serializer = 'json'
timezone = "UTC"
# define periodic tasks / cron here
# beat_schedule = {
#    'add-every-10-seconds': {
#        'task': 'workers.add_together',
#        'schedule': 10.0,
#        'args': (16, 16)
#    },
# }

现在在base/utility/celery_util.py文件中定义init_celery ：

# -*- coding: utf-8 -*-
def init_celery(app, celery):
    """Add flask app context to celery.Task"""
    TaskBase = celery.Task
    class ContextTask(TaskBase):
        abstract = True
        def __call__(self, *args, **kwargs):
            with app.app_context():
                return TaskBase.__call__(self, *args, **kwargs)
    celery.Task = ContextTask

对于以下方面的工人base/tasks/workers.py：

from base import celery as celery_app
from flask_security.utils import config_value, send_mail
from base.bp.users.models.user_models import User
from base.extensions import mail # this is the flask-mail
@celery_app.task
def send_async_email(msg):
    """Background task to send an email with Flask-mail."""
    #with app.app_context():
    mail.send(msg)
@celery_app.task
def send_welcome_email(email, user_id, confirmation_link):
    """Background task to send a welcome email with flask-security's mail.
    You don't need to use with app.app_context() here. Task has context.
    """
    user = User.query.filter_by(id=user_id).first()
    print(f'sending user {user} a welcome email')
    send_mail(config_value('EMAIL_SUBJECT_REGISTER'),
              email,
              'welcome', user=user,
              confirmation_link=confirmation_link)