Sending Confirmation Emails with Flask, RQ (Working outside of application context.) - flask

Question

I am trying to send confirmation emails when a new user registers. When I send a confirmation email, everything works fine, however, when I try to run that task in the background I get the following error:
File "/Users/martifont/Dev/bz/./FlaskApp/utils.py", line 22, in send_confirmation_email
msg = Message()
I have tried running a different task in the background with no issues at all.
users.py
#imports
from .utils import send_reset_email, send_confirmation_email, example
users = Blueprint('users', __name__)
#SIGNUP
#users.route('/signup', methods=\['GET', 'POST'\])
def signup():
form = SignupForm()
if form.validate_on_submit():
user = User(email=form.email.data, username=form.username.data, confirmed=False, is_admin=False, password = generate_password_hash(form.password.data, method='sha256'))
db.session.add(user)
db.session.commit()
user_id=user.id
with app.app_context():
job = q.enqueue(send_confirmation_email, user)
login_user(user)
flash('A confirmation email has been sent to your inbox.', 'is-success')
return redirect(url_for('users.account', id=user.id))
return render_template('signup.html', form=form)
utils.py
def send_confirmation_email(user):
token = user.get_confirmation_token()
msg = Message()
msg.subject = ('Email Confirmation')
msg.sender = 'MAIL_DEFAULT_SENDER'
msg.recipients = [user.email]
msg.body = f'''
Welcome { user.username }!,
Thanks for signing up. Please follow this link to activate your account:
{url_for('users.confirm_email', token=token, _external=True)}
Thanks!
'''
mail.send(msg)
EDIT
After following Sebastian's advice, I think the issue is solved, however, I am still getting the following error message.
File "/Users/martifont/Dev/bz/venv/lib/python3.10/site-packages/flask/app.py", line 2548, in __call__
return self.wsgi_app(environ, start_response)
File "/Users/martifont/Dev/bz/venv/lib/python3.10/site-packages/flask/app.py", line 2528, in wsgi_app
response = self.handle_exception(e)
File "/Users/martifont/Dev/bz/venv/lib/python3.10/site-packages/flask/app.py", line 2525, in wsgi_app
response = self.full_dispatch_request()
File "/Users/martifont/Dev/bz/venv/lib/python3.10/site-packages/flask/app.py", line 1822, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/Users/martifont/Dev/bz/venv/lib/python3.10/site-packages/flask/app.py", line 1820, in full_dispatch_request
rv = self.dispatch_request()
File "/Users/martifont/Dev/bz/venv/lib/python3.10/site-packages/flask/app.py", line 1796, in dispatch_request
return self.ensure_sync(self.view_functions[rule.endpoint])(**view_args)
File "/Users/martifont/Dev/bz/FlaskApp/users.py", line 30, in signup
job = q.enqueue(send_confirmation_email, args=(app, user))
File "/Users/martifont/Dev/bz/venv/lib/python3.10/site-packages/rq/queue.py", line 514, in enqueue
return self.enqueue_call(
File "/Users/martifont/Dev/bz/venv/lib/python3.10/site-packages/rq/queue.py", line 410, in enqueue_call
return self.enqueue_job(job, pipeline=pipeline, at_front=at_front)
File "/Users/martifont/Dev/bz/venv/lib/python3.10/site-packages/rq/queue.py", line 572, in enqueue_job
job.save(pipeline=pipe)
File "/Users/martifont/Dev/bz/venv/lib/python3.10/site-packages/rq/job.py", line 694, in save
mapping = self.to_dict(include_meta=include_meta)
File "/Users/martifont/Dev/bz/venv/lib/python3.10/site-packages/rq/job.py", line 629, in to_dict
'data': zlib.compress(self.data),
File "/Users/martifont/Dev/bz/venv/lib/python3.10/site-packages/rq/job.py", line 305, in data
self._data = self.serializer.dumps(job_tuple)

Answer 1

When you are in a view or inside the creat_app factory function there is no need to use the app_context() context manager.
The traceback defines where the error is been emited and that is when you instantiated the msg=Message() variable so instead of calling the app context inside the view i suggest you to refactor your view and send functions like so:
users.py
from flask import current_app
#users.route('/signup', methods=\['GET', 'POST'\])
def signup():
form = SignupForm()
if form.validate_on_submit():
user = User(email=form.email.data, username=form.username.data, confirmed=False, is_admin=False, password = generate_password_hash(form.password.data, method='sha256'))
db.session.add(user)
db.session.commit()
user_id=user.id
# pass the current app object to the send_confirmation_email function.
# Its important to pass the object and no the proxy
app = current_app._get_current_object()
job = q.enqueue(send_confirmation_email, args=(app, user))
login_user(user)
flash('A confirmation email has been sent to your inbox.', 'is-success')
return redirect(url_for('users.account', id=user.id))
return render_template('signup.html', form=form)
utils.py
def send_confirmation_email(app, user):
with app.app_context():
token = user.get_confirmation_token()
msg = Message()
msg.subject = ('Email Confirmation')
msg.sender = 'MAIL_DEFAULT_SENDER'
msg.recipients = [user.email]
msg.body = f'''
Welcome { user.username }!,
Thanks for signing up. Please follow this link to activate your account:
{url_for('users.confirm_email', token=token, _external=True)}
Thanks!'''
mail.send(msg)