Change how we use the send pending email task

backend/notifications/models.py

@@ -192,7 +192,7 @@ def send_email(
         if not recipient and not recipient_email:
             raise ValueError("Either recipient or recipient_email must be provided")
 
-        from notifications.tasks import send_pending_emails
+        from notifications.tasks import send_pending_email
 
         recipient_email = recipient_email or recipient.email
 
@@ -207,7 +207,7 @@ def send_email(
                 or settings.DEFAULT_FROM_EMAIL
             )
 
-        SentEmail.objects.create(
+        sent_email = SentEmail.objects.create(
             email_template=self,
             conference=self.conference,
             from_email=from_email,
@@ -223,7 +223,7 @@ def send_email(
             bcc_addresses=self.bcc_addresses,
         )
 
-        transaction.on_commit(lambda: send_pending_emails.delay())
+        transaction.on_commit(lambda: send_pending_email.delay(sent_email.id))
 
     @property
     def is_custom(self):

backend/notifications/tasks.py

@@ -1,59 +1,63 @@
+from django.db import transaction
+
 import logging
 from uuid import uuid4
-from pycon.celery_utils import OnlyOneAtTimeTask
 from notifications.models import SentEmail
-from django.db import transaction
 from pycon.celery import app
 from django.core.mail import EmailMultiAlternatives
 from django.core.mail import get_connection
 
 logger = logging.getLogger(__name__)
 
 
-@app.task(base=OnlyOneAtTimeTask)
-def send_pending_emails():
-    pending_emails = (
-        SentEmail.objects.pending().order_by("created").values_list("id", flat=True)
+def send_pending_email_failed(self, exc, task_id, args, kwargs, einfo):
+    sent_email_id = args[0]
+
+    sent_email = SentEmail.objects.get(id=sent_email_id)
+    sent_email.mark_as_failed()
+    logger.error(
+        "Failed to send email sent_email_id=%s",
+        sent_email.id,
     )
-    total_pending_emails = pending_emails.count()
 
-    if total_pending_emails == 0:
-        return
 
-    logger.info("Found %s pending emails", pending_emails.count())
+@app.task(
+    bind=True,
+    autoretry_for=(Exception,),
+    retry_backoff=True,
+    max_retries=5,
+    default_retry_delay=2,
+    on_failure=send_pending_email_failed,
+)
+@transaction.atomic()
+def send_pending_email(self, sent_email_id: int):
+    logger.info(
+        "Sending sent_email=%s (attempt=%s of %s)",
+        sent_email_id,
+        self.request.retries,
+        self.max_retries,
+    )
 
-    email_backend_connection = get_connection()
+    sent_email = (
+        SentEmail.objects.select_for_update(skip_locked=True)
+        .pending()
+        .filter(id=sent_email_id)
+        .first()
+    )
 
-    for email_id in pending_emails.iterator():
-        with transaction.atomic():
-            sent_email = (
-                SentEmail.objects.select_for_update(skip_locked=True)
-                .filter(
-                    id=email_id,
-                )
-                .first()
-            )
+    if not sent_email:
+        return
 
-            if not sent_email or not sent_email.is_pending:
-                return
+    email_backend_connection = get_connection()
 
-            try:
-                message_id = send_email(sent_email, email_backend_connection)
-                sent_email.mark_as_sent(message_id)
+    message_id = send_email(sent_email, email_backend_connection)
+    sent_email.mark_as_sent(message_id)
 
-                logger.info(
-                    "Email sent_email_id=%s sent with message_id=%s",
-                    sent_email.id,
-                    message_id,
-                )
-            except Exception as e:
-                sent_email.mark_as_failed()
-                logger.exception(
-                    "Failed to send email sent_email_id=%s error=%s",
-                    email_id,
-                    e,
-                    exc_info=e,
-                )
+    logger.info(
+        "Email sent_email_id=%s sent with message_id=%s",
+        sent_email.id,
+        message_id,
+    )
 
 
 def send_email(sent_email, email_backend_connection):

backend/notifications/tests/test_models.py

@@ -52,8 +52,8 @@ def test_send_email_template_to_recipient_email(
         reply_to="[email protected]",
     )
 
-    mock_send_pending_emails = mocker.patch(
-        "notifications.tasks.send_pending_emails.delay"
+    mock_send_pending_email = mocker.patch(
+        "notifications.tasks.send_pending_email.delay"
     )
 
     with django_capture_on_commit_callbacks(execute=True):
@@ -64,12 +64,12 @@ def test_send_email_template_to_recipient_email(
             },
         )
 
-    mock_send_pending_emails.assert_called_once()
-
     sent_email = SentEmail.objects.get(
         email_template=email_template,
     )
 
+    mock_send_pending_email.assert_called_once_with(sent_email.id)
+
     assert sent_email.recipient is None
     assert sent_email.recipient_email == "[email protected]"
 

backend/notifications/tests/test_tasks.py

@@ -1,23 +1,24 @@
+import smtplib
 from unittest.mock import patch
+from uuid import uuid4
 import time_machine
 from django.core import mail
-from notifications.tasks import send_pending_emails
+from notifications.tasks import send_pending_email, send_pending_email_failed
 from notifications.models import SentEmail
 from notifications.tests.factories import SentEmailFactory
 
 
-def test_send_pending_emails_does_nothing_with_no_pending_emails():
-    SentEmailFactory(status=SentEmail.Status.sent, sent_at="2020-01-01 12:00Z")
-    SentEmailFactory(status=SentEmail.Status.sent, sent_at="2020-01-01 12:00Z")
-    SentEmailFactory(status=SentEmail.Status.sent, sent_at="2020-01-01 12:00Z")
-    SentEmailFactory(status=SentEmail.Status.sent, sent_at="2020-01-01 12:00Z")
+def test_send_pending_email_does_nothing_with_non_pending_email():
+    sent_email = SentEmailFactory(
+        status=SentEmail.Status.sent, sent_at="2020-01-01 12:00Z"
+    )
 
-    send_pending_emails()
+    send_pending_email(sent_email.id)
 
     assert len(mail.outbox) == 0
 
 
-def test_send_pending_emails_task_sends_data_correctly():
+def test_send_pending_email_task_sends_data_correctly():
     pending_email_1 = SentEmailFactory(
         status=SentEmail.Status.pending,
         reply_to="[email protected]",
@@ -29,7 +30,8 @@ def test_send_pending_emails_task_sends_data_correctly():
         subject="subject",
     )
 
-    send_pending_emails()
+    with time_machine.travel("2021-01-01 12:00Z", tick=False):
+        send_pending_email(pending_email_1.id)
 
     assert len(mail.outbox) == 1
 
@@ -42,8 +44,16 @@ def test_send_pending_emails_task_sends_data_correctly():
     assert mail.outbox[0].alternatives == [("html body", "text/html")]
     assert mail.outbox[0].subject == "subject"
 
+    pending_email_1.refresh_from_db()
+
+    assert len(mail.outbox) == 1
+
+    assert pending_email_1.status == SentEmail.Status.sent
+    assert pending_email_1.message_id.startswith("local-")
+    assert pending_email_1.sent_at.isoformat() == "2021-01-01T12:00:00+00:00"
+
 
-def test_send_pending_emails_task_doesnt_double_send():
+def test_send_pending_email_task_doesnt_double_send():
     pending_email_1 = SentEmailFactory(status=SentEmail.Status.pending)
     original_qs = SentEmail.objects.select_for_update(skip_locked=True).filter(
         id=pending_email_1.id
@@ -57,81 +67,28 @@ def side_effect(*args, **kwargs):
         "notifications.tasks.SentEmail.objects.select_for_update",
         side_effect=side_effect,
     ):
-        send_pending_emails()
+        send_pending_email(pending_email_1.id)
 
     pending_email_1.refresh_from_db()
 
     assert len(mail.outbox) == 0
 
 
-def test_send_pending_emails_task():
-    pending_email_1 = SentEmailFactory(status=SentEmail.Status.pending)
-    pending_email_2 = SentEmailFactory(status=SentEmail.Status.pending)
-    sent_email_1 = SentEmailFactory(
-        status=SentEmail.Status.sent, message_id="abc-abc", sent_at="2020-01-01 12:00Z"
-    )
-
-    with time_machine.travel("2021-01-01 12:00Z", tick=False):
-        send_pending_emails()
-
-    pending_email_1.refresh_from_db()
-    pending_email_2.refresh_from_db()
-    sent_email_1.refresh_from_db()
-
-    assert len(mail.outbox) == 2
-
-    assert mail.outbox[0].to == [pending_email_1.recipient_email]
-    assert mail.outbox[1].to == [pending_email_2.recipient_email]
-
-    assert pending_email_1.status == SentEmail.Status.sent
-    assert pending_email_1.message_id.startswith("local-")
-    assert pending_email_1.sent_at.isoformat() == "2021-01-01T12:00:00+00:00"
-
-    assert pending_email_2.status == SentEmail.Status.sent
-    assert pending_email_2.message_id.startswith("local-")
-    assert pending_email_2.sent_at.isoformat() == "2021-01-01T12:00:00+00:00"
-
-    assert sent_email_1.status == SentEmail.Status.sent
-    assert sent_email_1.message_id == "abc-abc"
-    assert sent_email_1.sent_at.isoformat() == "2020-01-01T12:00:00+00:00"
-
-
-def test_send_pending_emails_handles_failures(mocker):
+def test_send_pending_email_failure():
     pending_email_1 = SentEmailFactory(
         status=SentEmail.Status.pending, created="2020-01-01 12:00Z"
     )
-    pending_email_2 = SentEmailFactory(
-        status=SentEmail.Status.pending, created="2020-01-02 12:00Z"
-    )
-
-    original_method = SentEmail.mark_as_sent
-
-    def _side_effect(*args, **kwargs):
-        if _side_effect.counter == 0:
-            _side_effect.counter = 1
-            raise ValueError("test")
 
-        return original_method(pending_email_2, *args, **kwargs)
-
-    _side_effect.counter = 0
-
-    mocker.patch("notifications.tasks.SentEmail.mark_as_sent", side_effect=_side_effect)
-
-    with time_machine.travel("2021-01-01 12:00Z", tick=False):
-        send_pending_emails()
+    send_pending_email_failed(
+        None,
+        smtplib.SMTPException("test"),
+        uuid4().hex,
+        (pending_email_1.id,),
+        {},
+        None,
+    )
 
     pending_email_1.refresh_from_db()
-    pending_email_2.refresh_from_db()
-
-    assert len(mail.outbox) == 2
-
-    assert mail.outbox[0].to == [pending_email_1.recipient_email]
-    assert mail.outbox[1].to == [pending_email_2.recipient_email]
 
+    assert len(mail.outbox) == 0
     assert pending_email_1.status == SentEmail.Status.failed
-    assert pending_email_1.message_id == ""
-    assert pending_email_1.sent_at is None
-
-    assert pending_email_2.status == SentEmail.Status.sent
-    assert pending_email_2.message_id.startswith("local-")
-    assert pending_email_2.sent_at.isoformat() == "2021-01-01T12:00:00+00:00"

backend/pycon/celery.py

@@ -24,7 +24,6 @@ def setup_periodic_tasks(sender, **kwargs):
     from schedule.tasks import process_schedule_items_videos_to_upload
     from files_upload.tasks import delete_unused_files
     from pycon.tasks import check_for_idle_heavy_processing_workers
-    from notifications.tasks import send_pending_emails
 
     add = sender.add_periodic_task
 
@@ -48,8 +47,3 @@ def setup_periodic_tasks(sender, **kwargs):
         check_for_idle_heavy_processing_workers,
         name="Check for idle heavy processing workers",
     )
-    add(
-        timedelta(minutes=1),
-        send_pending_emails,
-        name="Send pending emails",
-    )