Django中web开发使用模块celery的异步发送邮件

celery的基础用法可以参考之前转载的文章：
https://blog.csdn.net/ATOOHOO/article/details/88976521

1、编写异步任务队列文件：

celery 按照固定的套路是可以编写出一下的程序的，中间人使用的是Redis，其他的RabbitMQ等也是可以，可以参考官方文档：
http://docs.celeryproject.org/en/latest/getting-started/brokers/index.html#broker-overview

from django.core.mail import send_mail
from django.conf import settings
from celery import Celery
import time

# django环境的初始化，在任务处理者worker一端加以下几句
import os
import django
os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'dailyfresh.settings')
django.setup()

# 创建一个Celery类的实例对象,celery_tasks.tasks可以随便取一个名字，但是一般取有意义的名字
app = Celery('celery_tasks.tasks', broker='redis://127.0.0.1:6379/8')


# 定义任务函数
@app.task
def send_register_active_email(to_email, username, token):
    """发送激活邮件"""
    # 组织邮件信息
    subject = '天天生鲜欢迎信息'
    message = ''
    sender = settings.EMAIL_PROM  # 发送人
    receiver = [to_email]
    html_message = '
%s, 欢迎您成为天天生鲜注册会员
请点击下面链接激活您的账户
http://127.0.0.1:8000/user/active/%s' % (username, token, token)

    send_mail(subject, message, sender, receiver, html_message=html_message)
    # time.sleep(5)

celery中的一个很重要的角色是worker，集合Django实用的话，会用到Django中的一些配置，所以需要引入配置信息：

# django环境的初始化，在任务处理者worker一端加以下几句
import os
import django
os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'dailyfresh.settings')
django.setup()

否则的话会报出下面的错误信息，说是没能找到Django的配置信息：

[2019-08-20 18:10:45,039: INFO/MainProcess] Received task: celery_tasks.tasks.send_register_active_email[92d688f5-a42e-441a-8676-08eb2f480c8b]  
[2019-08-20 18:10:45,148: ERROR/ForkPoolWorker-2] Task celery_tasks.tasks.send_register_active_email[92d688f5-a42e-441a-8676-08eb2f480c8b] raised unexpected: ImproperlyConfigured('Requested setting EMAIL_PROM, but settings are not configured. You must either define the environment variable DJANGO_SETTINGS_MODULE or call settings.configure() before accessing settings.',)
Traceback (most recent call last):
  File "/home/toohoo/.local/lib/python3.6/site-packages/celery/app/trace.py", line 385, in trace_task
    R = retval = fun(*args, **kwargs)
  File "/home/toohoo/.local/lib/python3.6/site-packages/celery/app/trace.py", line 648, in __protected_call__
    return self.run(*args, **kwargs)
  File "/home/toohoo/PycharmProjects/mydailyfresh/celery_tasks/tasks.py", line 22, in send_register_active_email
    sender = settings.EMAIL_PROM  # 发送人
  File "/usr/local/lib/python3.6/dist-packages/django/conf/__init__.py", line 56, in __getattr__
    self._setup(name)
  File "/usr/local/lib/python3.6/dist-packages/django/conf/__init__.py", line 39, in _setup
    % (desc, ENVIRONMENT_VARIABLE))
django.core.exceptions.ImproperlyConfigured: Requested setting EMAIL_PROM, but settings are not configured. You must either define the environment variable DJANGO_SETTINGS_MODULE or call settings.configure() before accessing settings.

在主要的view里面调用队列发送邮件：

# 获取username
username = ...
# 获取email
email = ...
# 定义好token
token = ...
# 开始调用异步队列发送邮件celery:异步执行任务
send_register_active_email.delay(email, username, token)

注意： 不要漏掉使用delay()函数，否则如果使用send_register_active_email(email, username, token)的话依然是使用Django内置的邮件模块帮我们发的邮件！

启动成功和发送成功之后的信息：

(venv) toohoo@ubuntu:~/PycharmProjects/mydailyfresh$ celery -A celery_tasks.tasks worker -l info
 
 -------------- celery@ubuntu v4.3.0 (rhubarb)
---- **** ----- 
--- * ***  * -- Linux-4.15.0-58-generic-x86_64-with-Ubuntu-18.04-bionic 2019-08-20 18:42:53
-- * - **** --- 
- ** ---------- [config]
- ** ---------- .> app:         celery_tasks.tasks:0x7febbecf5198
- ** ---------- .> transport:   redis://127.0.0.1:6379/8
- ** ---------- .> results:     disabled://
- *** --- * --- .> concurrency: 2 (prefork)
-- ******* ---- .> task events: OFF (enable -E to monitor tasks in this worker)
--- ***** ----- 
 -------------- [queues]
                .> celery           exchange=celery(direct) key=celery
                

[tasks]
  . celery_tasks.tasks.send_register_active_email

[2019-08-20 18:42:53,989: INFO/MainProcess] Connected to redis://127.0.0.1:6379/8
[2019-08-20 18:42:54,002: INFO/MainProcess] mingle: searching for neighbors
[2019-08-20 18:42:55,028: INFO/MainProcess] mingle: all alone
[2019-08-20 18:42:55,046: WARNING/MainProcess] /home/toohoo/PycharmProjects/mydailyfresh/venv/lib/python3.6/site-packages/celery/fixups/django.py:202: UserWarning: Using settings.DEBUG leads to a memory leak, never use this setting in production environments!
  warnings.warn('Using settings.DEBUG leads to a memory leak, never '
[2019-08-20 18:42:55,046: INFO/MainProcess] celery@ubuntu ready.
[2019-08-20 18:44:00,183: INFO/MainProcess] Received task: celery_tasks.tasks.send_register_active_email[c3c4d266-838e-4955-ac39-f0ca38cf0463]  
[2019-08-20 18:44:06,714: INFO/ForkPoolWorker-2] Task celery_tasks.tasks.send_register_active_email[c3c4d266-838e-4955-ac39-f0ca38cf0463] succeeded in 6.527261982992059s: None

项目代码和地址为：
https://github.com/too-hoo/mydailyfresh