I'm using Flask Mail to send emails from my Flask App. No problem using it from the main thread. However I have a route that can send a quite large amount of emails (enough I think to exceed the HTTP Timeout) and I'd like to quickly return a response and running the mail send in the background.
I tried the following solution :
from concurrent.futures import ThreadPoolExecutor
executor = ThreadPoolExecutor(max_workers=1)
mailer = Mail(app) #Flask Mail Mailer
@app.route("/admin/sendmails")
def sendmails():
#
# Code to get recipients from DB here
#
executor.submit(send_links,recipients,mailer)
return "Mail sending began"
Here is the code for the send_mails function :
def send_links(recipients,mailing=None):
subject = "My subject"
if mailing == None : return logger.warning("No mailing available : Login links could not be sent")
with mailing.connect() as conn:
for [recipient,token,fullname] in recipients:
try:
raw_body = render_template("mails/login.txt",token=token, fullname=fullname)
html_body = render_template("mails/login.html",token=token, fullname=fullname)
msg = Message(subject,
recipients=[recipient])
msg.body = raw_body
msg.html = html_body
msg.attach('logo.png','image/png',open(os.path.join(os.path.dirname(os.path.abspath(__file__)),'static/image/logo.png'), 'rb').read(), 'inline', [['Content-ID', '<LOGO>']])
conn.send(msg)
except Exception as e:
logger.warning("Impossible to send login token \"{}\" to {}".format(token, fullname))
logger.warning(traceback.format_exc())
return True
However the send_links function uses render_template from within the Flask context (and the mailer probably uses it as well I guess) so I get the following error...
Traceback (most recent call last):
File "/var/www/rbt-rdd/server/utils.py", line 114, in send_links
raw_body = render_template("mails/login.txt",token=token, fullname=fullname)
File "/var/www/rbt-rdd/venv/lib/python3.9/site-packages/flask/templating.py", line 146, in render_template
ctx.app.update_template_context(context)
AttributeError: 'NoneType' object has no attribute 'app'
Do you have any idea how to fix this ?
Manually push a context:
def send_links(recipients, mailing=None):
# ... # -
with app.app_context(): # +
... # +
Reference: https://flask.palletsprojects.com/en/2.0.x/appcontext/#manually-push-a-context
You can implement it as a decorator, especially if you have many such functions:
from functools import wraps
def with_app_context(func):
@wraps(func)
def _func(*args, **kwargs):
with app.app_context():
return func(*args, **kwargs)
return _func
Usage:
@with_app_context # +
def send_links(recipients, mailing=None):
...