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Task Queue Example With Celery and Redis
import logging
import datetime
import smtplib
import ssl
from typing import Optional
from celery import Celery
#from celery.schedules import crontab
REDIS_BASE_URL = 'redis://localhost:6379'
SMTP_SERVER = "your.smtp.server"
SENDER_EMAIL = "your@email.com"
EMAIL_PASSWORD = "Secret_Email_Password"
app = Celery(
'runner',
broker=f"{REDIS_BASE_URL}/0",
backend=f"{REDIS_BASE_URL}/1"
)
app.conf.beat_schedule = {
'renew-expired-subscriptions': {
'task': 'runner.renew_expired_subscriptions',
'schedule': 5.0, # Runs in every 5 seconds
#'schedule': crontab(minute=5) # Runs in every 5 minutes
#'args': (arg_1, arg_2, ...), # Run the function with arguments
},
}
@app.task(name='renew-expired-subscriptions')
def renew_expired_subscriptions():
# Get expired user informations from your db
# Try to renew subscription
_test_user_info = {
'name': 'Test User',
'subscription_price': 14.99,
'renewal_date': datetime.datetime.strftime(
datetime.datetime.utcnow(),
'%Y-%m-%d %H:%M:%S'
)
}
_renewed = True # Very optimistic assumption
_test_user_email = 'test@user.com'
if _renewed:
_sent = send_email(
_test_user_email,
replace_fields_with_values(
'invoice_email_template',
_test_user_info
)
)
else:
_sent = send_email(
_test_user_email,
replace_fields_with_values(
'failed_to_renew_subscription_template',
_test_user_info
)
)
if _sent:
logging.info(f"Invoice sent to user {_test_user_email}")
return {
"email": _test_user_email,
"subscription_renewed": _renewed,
"email_status": _sent
}
@app.task(
name='send-email-to-user',
default_retry_delay=300,
max_retry=5,
soft_time_limit=30
)
def send_email_to_user(
user_email: str,
email_template: str,
extra_info: dict
):
_message = replace_fields_with_values(email_template, extra_info)
_sent = send_email(user_email, _message)
logging.info(f"Sent {email_template} email to user <{user_email}>")
return {
"email": user_email,
"email_type": email_template,
"email_status": _sent
}
def send_email(to: str, message: str):
try:
context = ssl.create_default_context()
with smtplib.SMTP(SMTP_SERVER, 587) as server:
server.ehlo()
server.starttls(context=context)
server.ehlo()
server.login(SENDER_EMAIL, EMAIL_PASSWORD)
server.sendmail(SENDER_EMAIL, to, message)
return True
except Exception as _ex:
logging.error(str(_ex))
logging.critical(
"Error occured while trying to"\
f"send invoice to: <{to}>"
)
return False
def replace_fields_with_values(
email_template: str,
extra_info: dict
):
try:
with open(f"{email_template}.txt", 'r') as _template:
_template_text = _template.read()
_email = _template_text.format(**extra_info)
return _email
except FileNotFoundError:
logging.critical(f"Email template not found: <{email_template}.txt>")
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