[feature] Batch email notifications

openwisp_notifications/handlers.py

@@ -1,6 +1,7 @@
 import logging
 
 from celery.exceptions import OperationalError
+from celery.result import AsyncResult
 from django.contrib.auth import get_user_model
 from django.contrib.contenttypes.models import ContentType
 from django.core.cache import cache
@@ -26,6 +27,7 @@
 logger = logging.getLogger(__name__)
 
 EXTRA_DATA = app_settings.get_config()['USE_JSONFIELD']
+EMAIL_BATCH_INTERVAL = app_settings.get_config()['EMAIL_BATCH_INTERVAL']
 
 User = get_user_model()
 
@@ -161,39 +163,37 @@ def notify_handler(**kwargs):
     return notification_list
 
 
-@receiver(post_save, sender=Notification, dispatch_uid='send_email_notification')
-def send_email_notification(sender, instance, created, **kwargs):
-    # Abort if a new notification is not created
-    if not created:
-        return
-    # Get email preference of user for this type of notification.
+def can_send_email(instance):
+    # Get email preference of the user for this type of notification
     target_org = getattr(getattr(instance, 'target', None), 'organization_id', None)
     if instance.type and target_org:
         try:
             notification_setting = instance.recipient.notificationsetting_set.get(
                 organization=target_org, type=instance.type
             )
         except NotificationSetting.DoesNotExist:
-            return
+            return False
         email_preference = notification_setting.email_notification
     else:
-        # We can not check email preference if notification type is absent,
-        # or if target_org is not present
-        # therefore send email anyway.
+        # Send email anyway if notification type or target_org is absent
         email_preference = True
 
+    # Check if email is verified
     email_verified = instance.recipient.emailaddress_set.filter(
         verified=True, email=instance.recipient.email
     ).exists()
 
+    # Verify email preference and email verification status
     if not (email_preference and instance.recipient.email and email_verified):
-        return
+        return False
 
+    # Verify the email subject
     try:
         subject = instance.email_subject
     except NotificationRenderException:
-        # Do not send email if notification is malformed.
-        return
+        return False
+
+    # Get the URL and description
     url = instance.data.get('url', '') if instance.data else None
     description = instance.message
     if url:
@@ -203,25 +203,61 @@ def send_email_notification(sender, instance, created, **kwargs):
     else:
         target_url = None
     if target_url:
-        description += _('\n\nFor more information see %(target_url)s.') % {
-            'target_url': target_url
-        }
-
-    send_email(
-        subject,
-        description,
-        instance.message,
-        recipients=[instance.recipient.email],
-        extra_context={
-            'call_to_action_url': target_url,
-            'call_to_action_text': _('Find out more'),
-        },
-    )
+        description += _('\n\nFor more information see %(target_url)s.') % {'target_url': target_url}
 
-    # flag as emailed
-    instance.emailed = True
-    # bulk_update is used to prevent emitting post_save signal
-    Notification.objects.bulk_update([instance], ['emailed'])
+    return True, subject, description, target_url
+
+
+@receiver(post_save, sender=Notification, dispatch_uid='send_email_notification')
+def send_email_notification(sender, instance, created, **kwargs):
+    # Abort if a new notification is not created
+    if not created:
+        return
+
+    can_send, subject, description, target_url = can_send_email(instance)
+
+    if not can_send:
+        return
+
+    recipient_id = instance.recipient.id 
+    cache_key = f'email_batch_{recipient_id}'
+    cache_data = cache.get(cache_key, {'last_email_sent_time': None, 'batch_scheduled': False})
+    is_send_email = False
+
+    if cache_data['last_email_sent_time']:
+        if (timezone.now() - cache_data['last_email_sent_time']).seconds < EMAIL_BATCH_INTERVAL:
+            if not cache_data['batch_scheduled']:
+                # Schedule batch email notification task
+                tasks.batch_email_notification.apply_async((recipient_id,), countdown=EMAIL_BATCH_INTERVAL)
+                cache_data['batch_scheduled'] = True
+                cache.set(cache_key, cache_data, timeout=EMAIL_BATCH_INTERVAL)
+            return
+        else:
+            # If the interval has passed, send the email immediately
+            is_send_email = True
+            cache_data['last_email_sent_time'] = timezone.now()
+            cache_data['batch_scheduled'] = False
+    else:
+        # If no email has been sent yet, send the email immediately
+        is_send_email = True
+        cache_data['last_email_sent_time'] = timezone.now()
+
+    cache.set(cache_key, cache_data, timeout=EMAIL_BATCH_INTERVAL)
+    if is_send_email:
+        send_email(
+            subject,
+            description,
+            instance.message,
+            recipients=[instance.recipient.email],
+            extra_context={
+                'call_to_action_url': target_url,
+                'call_to_action_text': _('Find out more'),
+            },
+        )
+        # flag as emailed
+        instance.emailed = True
+        # bulk_update is used to prevent emitting post_save signal
+        Notification.objects.bulk_update([instance], ['emailed'])
 
 
 @receiver(post_save, sender=Notification, dispatch_uid='clear_notification_cache_saved')

openwisp_notifications/settings.py

@@ -37,6 +37,12 @@
     'openwisp-notifications/audio/notification_bell.mp3',
 )
 
+EMAIL_BATCH_INTERVAL = getattr(
+    settings,
+    'EMAIL_BATCH_INTERVAL',
+    30 * 60  # 30 minutes
+)
+
 # Remove the leading "/static/" here as it will
 # conflict with the "static()" call in context_processors.py.
 # This is done for backward compatibility.

openwisp_notifications/tasks.py

@@ -3,14 +3,21 @@
 from celery import shared_task
 from django.contrib.auth import get_user_model
 from django.contrib.contenttypes.models import ContentType
+from django.core.cache import cache
 from django.db.models import Q
 from django.db.utils import OperationalError
 from django.utils import timezone
 
 from openwisp_notifications import types
+from openwisp_notifications import settings as app_settings
+from openwisp_notifications import handlers
 from openwisp_notifications.swapper import load_model, swapper_load_model
+from openwisp_notifications import settings as app_settings
+from openwisp_utils.admin_theme.email import send_email
 from openwisp_utils.tasks import OpenwispCeleryTask
 
+EMAIL_BATCH_INTERVAL = app_settings.get_config()['EMAIL_BATCH_INTERVAL']
+
 User = get_user_model()
 
 Notification = load_model('Notification')
@@ -202,3 +209,15 @@ def delete_ignore_object_notification(instance_id):
     Deletes IgnoreObjectNotification object post it's expiration.
     """
     IgnoreObjectNotification.objects.filter(id=instance_id).delete()
+
+
+@shared_task(base=OpenwispCeleryTask)
+def batch_email_notification(instance_id):
+    # Get all unsent notifications for the user in the last 30 minutes
+    time_threshold = timezone.now() - timedelta(minutes=30)
+    unsent_notifications = Notification.objects.filter(
+        emailed=False,
+        recipient_id=instance_id,
+        created__gte=time_threshold
+    )
+    print("Sending email....")