Files
zulip/zerver/management/commands/deliver_scheduled_emails.py
Alex Vandiver 4c518c2bba scheduled_email: Consistently lock users table.
Only clear_scheduled_emails previously took a lock on the users before
removing them; make deliver_scheduled_emails do so as well, by using
prefetch_related to ensure that the table appears in the SELECT.  This
is not necessary for correctness, since all accesses of
ScheduledEmailUser first access the ScheduledEmail and lock it; it is
merely for consistency.

Since SELECT ... FOR UPDATE takes an UPDATE lock on all tables
mentioned in the SELECT, merely doing the prefetch is sufficient to
lock both tables; no `on=(...)` is needed to `select_for_update`.

This also does not address the pre-existing potential deadlock from
these two use cases, where both try to lock the same ScheduledEmail
rows in opposite orders.
2021-08-19 00:44:33 -07:00

57 lines
1.8 KiB
Python

"""\
Send email messages that have been queued for later delivery by
various things (at this time invitation reminders and day1/day2
followup emails).
This management command is run via supervisor.
"""
import logging
import time
from typing import Any
from django.conf import settings
from django.core.management.base import BaseCommand
from django.db import transaction
from django.utils.timezone import now as timezone_now
from zerver.lib.logging_util import log_to_file
from zerver.lib.send_email import EmailNotDeliveredException, deliver_scheduled_emails
from zerver.models import ScheduledEmail
## Setup ##
logger = logging.getLogger(__name__)
log_to_file(logger, settings.EMAIL_DELIVERER_LOG_PATH)
class Command(BaseCommand):
help = """Send emails queued by various parts of Zulip
for later delivery.
Run this command under supervisor.
Usage: ./manage.py deliver_scheduled_emails
"""
def handle(self, *args: Any, **options: Any) -> None:
while True:
found_rows = False
with transaction.atomic():
email_jobs_to_deliver = (
ScheduledEmail.objects.filter(scheduled_timestamp__lte=timezone_now())
.prefetch_related("users")
.select_for_update()
)
if email_jobs_to_deliver:
found_rows = True
for job in email_jobs_to_deliver:
try:
deliver_scheduled_emails(job)
except EmailNotDeliveredException:
logger.warning("%r not delivered", job)
# Less load on the db during times of activity,
# and more responsiveness when the load is low
if found_rows:
time.sleep(10)
else:
time.sleep(2)