Fixed #107 and fixed #125 -- Periodic cleanup tasks

doc/admin/installation.rst

@@ -9,6 +9,7 @@ To use pretix, the most minimal setup consists of:
 
 * **pretix** and the python packages it depends on
 * An **WSGI application server** (we recommend gunicorn)
+* A periodic task runner, e.g. ``cron``
 
 You get those two bundled in the ``pretix/standalone`` docker image.
 
@@ -40,3 +41,11 @@ If you want to use one of the payment providers shipping with pretix, you should
 
 We will provide a step-by-step tutorial with the first stable release, but all configuration
 already :ref:`is documented <config>`.
+
+Set up a cronjob
+----------------
+
+You need to set up a cronjob that runs the management command ``runperiodic``. The exact interval is not important
+but should be something between every minute and every hour. You could for example configure cron like this::
+
+    15,45 * * * * python3 /path/to/pretix/manage.py runperiodic

src/pretix/base/__init__.py

@@ -8,7 +8,7 @@ class PretixBaseConfig(AppConfig):
     def ready(self):
         from . import exporter  # NOQA
         from . import payment  # NOQA
-        from .services import export, mail, tickets, cart, orders  # NOQA
+        from .services import export, mail, tickets, cart, orders, cleanup  # NOQA
 
         try:
             from .celery import app as celery_app  # NOQA

src/pretix/base/management/commands/runperiodic.py

@@ -0,0 +1,12 @@
+from django.core.management import call_command
+from django.core.management.base import BaseCommand
+
+from ...signals import periodic_task
+
+
+class Command(BaseCommand):
+    help = "Run periodic tasks"
+
+    def handle(self, *args, **options):
+        periodic_task.send(self)
+        call_command('clearsessions')

src/pretix/base/models/orders.py

@@ -299,6 +299,11 @@ class QuestionAnswer(models.Model):
         else:
             return self.answer
 
+    def save(self, *args, **kwargs):
+        if self.orderposition and self.cartposition:
+            raise ValueError('QuestionAnswer cannot be linked to an order and a cart position at the same time.')
+        super().save(*args, **kwargs)
+
 
 class AbstractPosition(models.Model):
     """

src/pretix/base/services/cleanup.py

@@ -0,0 +1,21 @@
+from datetime import timedelta
+
+from django.dispatch import receiver
+from django.utils.timezone import now
+
+from ..models import CachedFile, CartPosition, InvoiceAddress
+from ..signals import periodic_task
+
+
+@receiver(signal=periodic_task)
+def clean_cart_positions(sender, **kwargs):
+    for cp in CartPosition.objects.filter(expires__lt=now() - timedelta(days=14)):
+        cp.delete()
+    for ia in InvoiceAddress.objects.filter(order__isnull=True, last_modified__lt=now() - timedelta(days=14)):
+        ia.delete()
+
+
+@receiver(signal=periodic_task)
+def clean_cached_files(sender, **kwargs):
+    for cf in CachedFile.objects.filter(expires__isnull=False, expires__lt=now()):
+        cf.delete()

src/pretix/base/signals.py

@@ -95,3 +95,13 @@ don't know how to turn it into human-readable text.
 logentry_display = EventPluginSignal(
     providing_args=["logentry"]
 )
+
+
+"""
+This is a regular django signal (no pretix event signal) that we send out every
+time the periodic task cronjob runs. This interval is not sharply defined, it can
+be everything between a minute and a day. The actions you perform should be
+idempotent, i.e. it should not make a difference if this is send out more often
+than expected.
+"""
+periodic_task = django.dispatch.Signal()