from os.path import join, abspath, exists
+from django.core.urlresolvers import reverse
from django.db import models
from waiter.settings import WAITER_ROOT, WAITER_URL
-from django.core.urlresolvers import reverse
+from djcelery.models import TaskMeta
+
class WaitedFile(models.Model):
path = models.CharField(max_length=255, unique=True, db_index=True)
Won't open a path leading outside of WAITER_ROOT.
"""
abs_path = cls.abspath(path)
- # Pre-fetch objects to avoid minor race condition
+ # Pre-fetch objects for deletion to avoid minor race condition
relevant = [o.id for o in cls.objects.filter(path=path)]
- print abs_path
if exists(abs_path):
cls.objects.filter(id__in=relevant).delete()
return True
else:
return False
+ def is_stale(self):
+ if self.task is None:
+ # Race; just let the other task roll.
+ return False
+ try:
+ meta = TaskMeta.objects.get(task_id=self.task)
+ assert meta.status in (u'PENDING', u'STARTED', u'SUCCESS', u'RETRY')
+ except TaskMeta.DoesNotExist:
+ # Might happen it's not yet there.
+ pass
+ except AssertionError:
+ return True
+ return False
+
@classmethod
def order(cls, path, task_creator, description=None):
"""
Returns an URL for the user to follow.
If the file is ready, returns download URL.
If not, starts preparing it and returns waiting URL.
+
+ task_creator: function taking a path and generating the file;
+ description: a string or string proxy with a description for user;
"""
already = cls.exists(path)
if not already:
waited, created = cls.objects.get_or_create(path=path)
- if created:
- # TODO: makedirs
+ if created or waited.is_stale():
waited.task = task_creator(cls.abspath(path))
- print waited.task
waited.description = description
waited.save()
- # TODO: it the task exists, if stale delete, send some mail and restart
return reverse("waiter", args=[path])
return join(WAITER_URL, path)