users/management/commands/send_notifications.py

@@ -0,0 +1,38 @@
+"""Send user notifications as emails, at most once delivery."""
+from collections import defaultdict
+import logging
+
+from django.core.management.base import BaseCommand
+from django.utils import timezone
+
+from users.models import Notification
+
+logger = logging.getLogger(__name__)
+logger.setLevel(logging.INFO)
+
+
+class Command(BaseCommand):
+    def handle(self, *args, **options):  # noqa: D102
+        logger.info('start, checking for outstanding notifications')
+        notifications = Notification.objects.filter(processed_by_mailer_at=None)
+        batched_by_recipient = defaultdict(list)
+        for n in notifications:
+            batched_by_recipient[n.recipient].append(n)
+
+        for recipient, batch in batched_by_recipient.items():
+            to_send = []
+            for n in batch:
+                n.processed_by_mailer_at = timezone.now()
+                if recipient.is_subscribed(n):
+                    n.sent = True
+                    to_send.append(n)
+            # first mark, then send: to avoid spamming in case of a crash-loop
+            Notification.objects.bulk_update(batch, ['processed_by_mailer_at', 'sent'])
+            if len(to_send) > 0:
+                logger.info(f'sending an email to {recipient} about {len(to_send)} notifications')
+                send_email(recipient, to_send)
+        logger.info('finish')
+
+
+def send_email(recipient, to_send):
+    pass

users/migrations/0003_notification.py

@@ -0,0 +1,26 @@
+# Generated by Django 4.2.11 on 2024-04-12 12:06
+
+from django.conf import settings
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('actstream', '0003_add_follow_flag'),
+        ('users', '0002_moderators_group'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='Notification',
+            fields=[
+                ('id', models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('processed_by_mailer_at', models.DateTimeField(default=None, null=True)),
+                ('sent', models.BooleanField(default=False)),
+                ('action', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to='actstream.action')),
+                ('recipient', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to=settings.AUTH_USER_MODEL)),
+            ],
+        ),
+    ]

users/models.py

@@ -3,6 +3,7 @@ from typing import Optional
 import logging
 import time
 
+from actstream.models import Action
 from django.contrib.admin.utils import NestedObjects
 from django.contrib.auth.models import AbstractUser
 from django.db import models, DEFAULT_DB_ALIAS, transaction
@@ -139,3 +140,13 @@ class User(TrackChangesMixin, AbstractUser):
     def is_moderator(self):
         # Used to review and approve extensions
         return self.groups.filter(name='moderators').exists()
+
+    def is_subscribed(self, notification: 'Notification') -> bool:
+        return True
+
+
+class Notification(models.Model):
+    recipient = models.ForeignKey(User, null=False, on_delete=models.CASCADE)
+    action = models.ForeignKey(Action, null=False, on_delete=models.CASCADE)
+    processed_by_mailer_at = models.DateTimeField(default=None, null=True)
+    sent = models.BooleanField(default=False, null=False)

users/signals.py

@@ -10,8 +10,9 @@ from django.dispatch import receiver
 
 from blender_id_oauth_client import signals as bid_signals
 
-from users.blender_id import BIDSession
 from extensions.models import Extension
+from users.blender_id import BIDSession
+from users.models import Notification
 
 User = get_user_model()
 bid = BIDSession()
@@ -60,10 +61,7 @@ def create_notification(
 
     audience = filter(lambda f: f != instance.actor, followers(instance.target))
     for recipient in audience:
-        print(
+        Notification.objects.get_or_create(recipient=recipient, action=instance)
-            f'create notification for {recipient}: ',
-            f'{instance.actor} {instance.verb} {instance.target}',
-        )
 
 
 @receiver(m2m_changed, sender=User.groups.through)