Issue with using django celery when django signals is being used to sent email? - django

Question

I have used the default Django admin panel as my backend. I have a Blogpost model. What I am trying to do is whenever an admin user saves a blogpost object on Django admin, I need to send an email to the newsletter subscribers notifying them that there is a new blog on the website.
I have to send mass emails so I am using django-celery. Also, I am using django signals to trigger the send email function.
But Right now, I am sending without using celery but it is too slow.
class Subscribers(models.Model):
email = models.EmailField(unique=True)
date_subscribed = models.DateField(auto_now_add=True)
def __str__(self):
return self.email
class Meta:
verbose_name_plural = "Newsletter Subscribers"
# binding signal:
#receiver(post_save,sender=BlogPost)
def send_mails(sender,instance,created,**kwargs):
subscribers = Subscribers.objects.all()
if created:
blog = BlogPost.objects.latest('date_created')
for abc in subscribers:
emailad = abc.email
send_mail('New Blog Post ', f" Checkout our new blog with title {blog.title} ",
EMAIL_HOST_USER, [emailad],
fail_silently=False)
else:
return
Using celery documentation i have written following files.
My celery.py
from __future__ import absolute_import
import os
from celery import Celery
from django.conf import settings
os.environ.setdefault('DJANGO_SETTINGS_MODULE','travel_crm.settings')
app = Celery('travel_crm')
app.config_from_object('django.conf:settings')
app.autodiscover_tasks(lambda: settings.INSTALLED_APPS)
#app.task(bind=True)
def debug_task(self):
print('Request: {0!r}'.format(self.request))
Mu init file:
from __future__ import absolute_import, unicode_literals
from .celery import app as celery_app
__all__ = ('celery_app',)
Tasks file from docs:
def my_first_task(duration):
subject= 'Celery'
message= 'My task done successfully'
receiver= 'receiver_mail#gmail.com'
is_task_completed= False
error=''
try:
sleep(duration)
is_task_completed= True
except Exception as err:
error= str(err)
logger.error(error)
if is_task_completed:
send_mail_to(subject,message,receivers)
else:
send_mail_to(subject,error,receivers)
return('first_task_done')
This task doesn't work because I am using Django signal to trigger the send email function, How to employ this into tasks.py

Answer 1

I think I understand your question ... I was recently faced with similar challenge which included the complexity of a multi-tenant [schema] database [proved to be an issue with Redis]. I also tried django-celery, but it is dependent on a much older version of Celery. In addition, I wanted to send mass mail initiated by model signal post_save ... using EmailMultiAlternatives with 'bcc' and 'reply-to' features.
So now I am using the latest [as of this post] Django, the latest Celery with Redis ... running on macOS localhost with Poetry virtual env & package manager. The following worked for me:
Celery: I spent several hours net searching for tutorials and advice ... among others, this one added value for me Celery w Django. Good practice to dig deeper into Celery anyway if you have not done it already.
Redis: This will depend on your OS and if you are developing local or remote. The Redis website will guide you to set up. I also tried RabbitMQ but found it [personally] more complex to set up.
The code fractions: There are 4 fractions ... myapp/signals.py, myapp/tasks.py, myproj/celery.py, myproj/settings.py Disclaimer: I'm a hobby programmer ... more experienced engineers may well improve on my code ... I've done some minor testing and all seems to work.
# myapp/signals.py
#receiver(post_save, sender=MyModel)
def post_save_handler(sender, instance, **kwargs):
if instance.some_field == True:
recipient_list = list(get_user_model().objects.filter('some filters'))
from_email = SomeModel.objects.first().site_email
to_email = SomeModel.first().admin_email
# call async task Celery
task_send_mail.delay(instance.some_field, instance.someother_field, from_email, to_email, recipient_list)
# myapp/tasks.py
#shared_task(name='task_sendmail')
def task_send_mail(instance.some_field, instance.someother_field, from_email, to_email, recipient_list):
template_name = 'emails/sometemplate.html'
html_message = render_to_string(template_name, {'body': instance.some_field,}) # These variables are added to the email template
plain_message = strip_tags(html_message)
subject = f'Do Not Reply : {instance.someother_field}'
connection = get_connection()
connection.open()
message = EmailMultiAlternatives(
subject,
plain_message,
from_email,
[to_email],
bcc=recipient_list,
reply_to=[to_email],
)
message.attach_alternative(html_message, "text/html")
try:
message.send()
connection.close()
except SMTPException as e:
print('There was an error sending email: ', e)
connection.close()
# myproj/celery.py
import os
from celery import Celery
# Set the default Django settings module for the 'celery' program.
os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'myproj.settings')
app = Celery('myproj')
# Using a string here means the worker doesn't have to serialize
# the configuration object to child processes.
# - namespace='CELERY' means all celery-related configuration keys
# should have a `CELERY_` prefix.
app.config_from_object('django.conf:settings', namespace='CELERY')
# Load task modules from all registered Django apps.
app.autodiscover_tasks()
#app.task(bind=True)
def debug_task(self):
print(f'Request: {self.request!r}')
# myproj/settings.py
...
##Celery Configuration Options
CELERY_BROKER_URL = 'redis://localhost:6379//'
CELERY_TIMEZONE = "Africa/SomeCity"
CELERY_TASK_TRACK_STARTED = True
CELERY_TASK_TIME_LIMIT = 30 * 60