old_contents: # -*- coding: utf-8 -*-
  # Copyright (C) 2014-2017 Andrey Antukh <niwi@niwi.nz>
  # Copyright (C) 2014-2017 Jesús Espino <jespinog@gmail.com>
  # Copyright (C) 2014-2017 David Barragán <bameda@dbarragan.com>
  # Copyright (C) 2014-2017 Alejandro Alonso <alejandro.alonso@kaleidos.net>
  # This program is free software: you can redistribute it and/or modify
  # it under the terms of the GNU Affero General Public License as
  # published by the Free Software Foundation, either version 3 of the
  # License, or (at your option) any later version.
  #
  # This program is distributed in the hope that it will be useful,
  # but WITHOUT ANY WARRANTY; without even the implied warranty of
  # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  # GNU Affero General Public License for more details.
  #
  # You should have received a copy of the GNU Affero General Public License
  # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  
  
  from django.core.management.base import BaseCommand
  
  from taiga.base.utils.iterators import iter_queryset
  from taiga.projects.notifications.models import HistoryChangeNotification
  from taiga.projects.notifications.services import send_sync_notifications
  
  class Command(BaseCommand):
  
      def handle(self, *args, **options):
          qs = HistoryChangeNotification.objects.all()
          for change_notification in iter_queryset(qs, itersize=100):
              try:
                  send_sync_notifications(change_notification.pk)
              except HistoryChangeNotification.DoesNotExist:
                  pass
  
new_contents: # -*- coding: utf-8 -*-
  # Copyright (C) 2014-2017 Andrey Antukh <niwi@niwi.nz>
  # Copyright (C) 2014-2017 Jesús Espino <jespinog@gmail.com>
  # Copyright (C) 2014-2017 David Barragán <bameda@dbarragan.com>
  # Copyright (C) 2014-2017 Alejandro Alonso <alejandro.alonso@kaleidos.net>
  # This program is free software: you can redistribute it and/or modify
  # it under the terms of the GNU Affero General Public License as
  # published by the Free Software Foundation, either version 3 of the
  # License, or (at your option) any later version.
  #
  # This program is distributed in the hope that it will be useful,
  # but WITHOUT ANY WARRANTY; without even the implied warranty of
  # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  # GNU Affero General Public License for more details.
  #
  # You should have received a copy of the GNU Affero General Public License
  # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  
  
  from django.core.management.base import BaseCommand
  
  from taiga.base.utils.iterators import iter_queryset
  from taiga.projects.notifications.models import HistoryChangeNotification
  from taiga.projects.notifications.services import send_sync_notifications
  
  from django_pglocks import advisory_lock
  
  class Command(BaseCommand):
  
      def handle(self, *args, **options):
          with advisory_lock("send-notifications-command", wait=False) as acquired:
              if acquired:
                  qs = HistoryChangeNotification.objects.all()
                  for change_notification in iter_queryset(qs, itersize=100):
                      try:
                          send_sync_notifications(change_notification.pk)
                      except HistoryChangeNotification.DoesNotExist:
                          pass
              else:
                  print("Other process already running")
  
subject: Add advisory lock to send_notifications