Django - Delete file from amazon S3

Question

I have a problem where deleting an object form the admin won't delete the file associated with it. after some research I decided to implement a post_delete in the model. For some reason I am not able to make the s3 delete the file, even after searching numerous guides and snippets, maybe someone here knows. I use django 1.5 and boto. Heres my code for the model:

from django.db import models
from django.contrib.auth.models import User
from fileservice.formatChecker import ContentTypeRestrictedFileField
from south.modelsinspector import add_introspection_rules
import os
from django.dispatch import receiver
from django.utils.translation import ugettext_lazy as _
from django.core.files.storage import default_storage as storage
add_introspection_rules([
    (
        [ContentTypeRestrictedFileField], # Class(es) these apply to
        [],         # Positional arguments (not used)
        {           # Keyword argument
            "content_types": ["content_types", {}],
            "max_upload_size": ["max_upload_size", {}]
        },
    ),
], ["^fileservice\.formatChecker\.ContentTypeRestrictedFileField"])

class Contentfile(models.Model):
    content = ContentTypeRestrictedFileField(upload_to='uploads/', content_types=['video/mp4', 'application/pdf', 'image/gif', 'image/jpeg', 'image/png'],max_upload_size=5242880,blank=True, null=True, help_text='Upload a file to add it to the content the app displayes')
    created_at = models.DateTimeField(auto_now_add=True, editable=False)
    updated_at = models.DateTimeField(auto_now=True, editable=False)
    title = models.CharField(max_length=255, unique=True)
    file_type = models.CharField(max_length=5)
    published = models.BooleanField(default=True)
    file_owner = models.ForeignKey(User, related_name='Contentfiles')

    class Meta:
        ordering = ["title"]

    def __unicode__(self):
        return self.title

    def save(self, *args, **kwargs):
        file_name = os.path.basename(self.content.name)
        self.file_type = file_name.split('.')[-1]
        self.title = file_name.split('.')[0]
        self.published = True
        super(Contentfile, self).save(*args, **kwargs)



@receiver(models.signals.post_delete, sender=Contentfile)
def auto_delete_file_on_delete(sender, instance, **kwargs):
    """Deletes file from filesystem
    when corresponding `MediaFile` object is deleted.
    """
    if instance.content:
        if os.path.isfile(storage.open(instance.content.path)):
            os.remove(storage.open(instance.content.path))

@receiver(models.signals.pre_save, sender=Contentfile)
def auto_delete_file_on_change(sender, instance, **kwargs):
    """Deletes file from filesystem
    when corresponding `MediaFile` object is changed.
    """
    if not instance.pk:
        return False

    try:
        old_file = Contentfile.objects.get(pk=instance.pk).content
    except Conentfile.DoesNotExist:
        return False

    new_file = instance.content
    if not old_file == new_file:
        if os.path.isfile(storage.open(old_file.path)):
            os.remove(storage.open(old_file.path))

Answer 1

It is MUCH safer to do post_delete. If something goes wrong you will start missing S3 files and you wont notice it because your DB records are intact. post_delete will be safer since it is less likely that S3 delete operation would fail after you have deleted your db record. Furthermore even if file delete fails you will be left with a bunch of unreferenced S3 file which are harmless and can be easily cleaned up.

@receiver(models.signals.post_delete, sender=Picture)
def remove_file_from_s3(sender, instance, using, **kwargs):
    instance.img.delete(save=False)

Answer 2

You need to call FieldFile's delete() method to remove the file in S3. In your case, add a pre_delete signal where you call it:

@receiver(models.signals.pre_delete, sender=ContentFile)
def remove_file_from_s3(sender, instance, using):
    instance.content.delete(save=False)

Answer 3

Try django-cleanup, it automatically invokes delete method on FileField when you remove model.