Services Notification

Multi-Channel Notification

from django.db import transaction

def send_firmware_approved_notification(
    *, firmware_id: int, user_id: int
) -> None:
    """Notify via in-app + email when firmware is approved."""
    # In-app notification
    notify_user(
        user_id=user_id,
        notification_type="firmware_approved",
        title="Firmware Approved",
        message="Your firmware submission has been approved.",
        action_url=f"/firmwares/{firmware_id}/",
    )
    # Queue email (async)
    transaction.on_commit(
        lambda: send_templated_email.delay(
            user_id=user_id,
            template_name="firmware_approved",
            context={"firmware_id": firmware_id},
        )
    )

Batch Notifications

def notify_subscribers(
    *, topic_id: int, reply_id: int, author_id: int
) -> int:
    """Notify all topic subscribers about a new reply."""
    subscriber_ids = list(
        ForumTopicSubscription.objects
        .filter(topic_id=topic_id, is_active=True)
        .exclude(user_id=author_id)  # Don't notify the author
        .values_list("user_id", flat=True)
    )
    notifications = [
        Notification(
            user_id=uid,
            notification_type="new_reply",
            title="New reply in subscribed topic",
            action_url=f"/forum/t/{topic_id}/#reply-{reply_id}",
        )
        for uid in subscriber_ids
    ]
    Notification.objects.bulk_create(notifications, batch_size=500)
    return len(notifications)

Mark as Read

def mark_notifications_read(*, user_id: int, notification_ids: list[int]) -> int:
    """Mark specific notifications as read."""
    return Notification.objects.filter(
        pk__in=notification_ids, user_id=user_id, is_read=False
    ).update(is_read=True)

def mark_all_read(*, user_id: int) -> int:
    return Notification.objects.filter(
        user_id=user_id, is_read=False
    ).update(is_read=True)

Anti-Patterns

• Sending emails synchronously inside request/response cycle
• Notifying users who have opted out of that notification type
• Creating notifications outside @transaction.atomic when paired with model changes
• Notifying the actor about their own action

Red Flags

• send_mail() called directly in a view without Celery
• No preference check before sending notifications
• Missing batch_size on bulk notification creation

Quality Gate

& .\.venv\Scripts\python.exe -m ruff check . --fix
& .\.venv\Scripts\python.exe -m ruff format .
& .\.venv\Scripts\python.exe manage.py check --settings=app.settings_dev