Question

I’m running the Google App Engine devserver 1.3.3 on Windows 7.

Usually, this method works fine, but this time it gave an error:

def _deleteType(type):
    results = type.all().fetch(1000)
    while results:
        db.delete(results)
        results = type.all().fetch(1000)

The error:

  File "src\modelutils.py", line 38, in _deleteType
    db.delete(results)
  File "C:\Program Files\Google\google_appengine\google\appengine\ext\db\__init__.py", line 1302, in delete
    datastore.Delete(keys, rpc=rpc)
  File "C:\Program Files\Google\google_appengine\google\appengine\api\datastore.py", line 386, in Delete
    'datastore_v3', 'Delete', req, datastore_pb.DeleteResponse(), rpc)
  File "C:\Program Files\Google\google_appengine\google\appengine\api\datastore.py", line 186, in _MakeSyncCall
    rpc.check_success()
  File "C:\Program Files\Google\google_appengine\google\appengine\api\apiproxy_stub_map.py", line 474, in check_success
    self.__rpc.CheckSuccess()
  File "C:\Program Files\Google\google_appengine\google\appengine\api\apiproxy_rpc.py", line 149, in _WaitImpl
    self.request, self.response)
  File "C:\Program Files\Google\google_appengine\google\appengine\api\datastore_file_stub.py", line 667, in MakeSyncCall
    response)
  File "C:\Program Files\Google\google_appengine\google\appengine\api\apiproxy_stub.py", line 80, in MakeSyncCall
    method(request, response)
  File "C:\Program Files\Google\google_appengine\google\appengine\api\datastore_file_stub.py", line 775, in _Dynamic_Delete
    self.__WriteDatastore()
  File "C:\Program Files\Google\google_appengine\google\appengine\api\datastore_file_stub.py", line 610, in __WriteDatastore
    self.__WritePickled(encoded, self.__datastore_file)
  File "C:\Program Files\Google\google_appengine\google\appengine\api\datastore_file_stub.py", line 656, in __WritePickled
    os.rename(tmpfile.name, filename)
WindowsError: [Error 183] Cannot create a file when that file already exists

What am I doing wrong? How could this have failed this time, but usually it doesn’t?

UPDATE I restarted the devserver, and when it came back online, the datastore was empty.

Answer 1

Unfortunately, 1.3.3 is too far back for me to look at its sources and try to diagnose your problem precisely – the SDK has no 1.3.3 release tag and I can’t guess which revision of the datastore_filestub.py was in 1.3.3. Can you upgrade to the current version, 1.3.5, and try again? Running old versions (especially 2+ versions back) is not recommended since they’ll be possibly a little out of sync with what’s actually available on Google’s actual servers, anyway (and/or have bugs that are fixed in later versions). Anyway…

On Windows, os.rename doesn’t work if the destination exists — but the revisions I see are careful to catch the OSError that results (WindowsError derives from it), remove the existing file, and try renaming again. So I don’t know what could explain your bug — if the sources of the SDK you’re running have that careful arrangement, and I think they do.

Plus, I’d recommend to --use_sqlite (see Nick Johnson’s blog announcing it here) in lieu of the file-stub for your SDK datastore – it just seems to make more sense!-)