Uploading to Google Cloud Storage from Django on App Engine

Question

I'm using Django 1.5 on Google App Engine and I'm trying to upload files to Google Cloud Storage. I'm using the gcs the library and have written a custom file upload handler that I've registered in settings.py as my only file uploader. I can see my file being correctly uploaded in the blobstore viewer in my development environment but once form.save() is called in views.py I get an exception thrown saying that it's a read only file system? I know Google App Engine doesn't allow access to the file system which is why I'm using GCS in the first place!

Is there something I need to do to stop Django from trying to save the file to disk?

The relevant code is attached in this gist.

Thanks :)

Stack Trace:

Environment:


Request Method: POST
Request URL: http://localhost:8080/cms/media/add

Django Version: 1.5
Python Version: 2.7.5
Installed Applications:
('django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.staticfiles',
 'django.contrib.messages',
 'api',
 'cms',
 'frontend')
Installed Middleware:
('django.middleware.common.CommonMiddleware',
 'django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware')


Traceback:
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/django-1.5/django/core/handlers/base.py" in get_response
  115.                         response = callback(request, *callback_args, **callback_kwargs)
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/django-1.5/django/contrib/auth/decorators.py" in _wrapped_view
  25.                 return view_func(request, *args, **kwargs)
File "/Users/james/Dropbox/University/Year 4/Advanced Development/assignment/cms/views.py" in media_add_or_edit
  44.             form.save()
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/django-1.5/django/forms/models.py" in save
  370.                              fail_message, commit, construct=False)
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/django-1.5/django/forms/models.py" in save_instance
  87.         instance.save()
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/django-1.5/django/db/models/base.py" in save
  546.                        force_update=force_update, update_fields=update_fields)
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/django-1.5/django/db/models/base.py" in save_base
  650.                 result = manager._insert([self], fields=fields, return_id=update_pk, using=using, raw=raw)
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/django-1.5/django/db/models/manager.py" in _insert
  215.         return insert_query(self.model, objs, fields, **kwargs)
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/django-1.5/django/db/models/query.py" in insert_query
  1673.     return query.get_compiler(using=using).execute_sql(return_id)
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/django-1.5/django/db/models/sql/compiler.py" in execute_sql
  936.         for sql, params in self.as_sql():
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/django-1.5/django/db/models/sql/compiler.py" in as_sql
  894.                 for obj in self.query.objs
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/django-1.5/django/db/models/fields/files.py" in pre_save
  250.             file.save(file.name, file, save=False)
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/django-1.5/django/db/models/fields/files.py" in save
  86.         self.name = self.storage.save(name, content)
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/django-1.5/django/core/files/storage.py" in save
  48.         name = self._save(name, content)
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/django-1.5/django/core/files/storage.py" in _save
  198.                     fd = os.open(full_path, flags, 0o666)
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/devappserver2/python/stubs.py" in fake_open
  71.     raise OSError(errno.EROFS, 'Read-only file system', filename)

Exception Type: OSError at /cms/media/add
Exception Value: [Errno 30] Read-only file system: u'/Users/james/Dropbox/University/Year 4/Advanced Development/assignment/IMG_0746.jpg'

Answer 1

I eventually solved this by moving the FileField from my Model into my ModelForm like so:

# Used for uploading media that forms part of a story
class Media(models.Model):
    title = models.CharField(max_length=100)
    type = models.CharField(max_length=5, choices=MEDIA_TYPES)
    content = models.TextField()
    date_created = models.DateTimeField(auto_now_add=True)

# Used to convert the media model to a form in the cms
class MediaForm(forms.ModelForm):
    file = forms.FileField()

    class Meta:
        model = Media
        # Don't show the date created field because we want that to be set automatically
        exclude = ('date_created', 'content',)

I'm sure I tried that before but it appears to have fixed my issue, hopefully this might help someone else who runs into the same problem.