Different python ProtocolBuffer implementations on dev and prod

[Alex Burgel]

Hi,

I've been pickling some data to store in a datastore blob, and recently I tried to download and unpickle the data on my local machine. I got errors whenever I tried to do this because it seems like production uses a different version of ProtocolBuffers than the SDK.

Part of the pickled data contained an appengine Key, which contains a reference to a google.appengine.datastore.entity_pb.Reference, which is a subclass of google.net.proto.ProtocolBuffer.ProtocolMessage. On the SDK, this is old-style python class. But it looks like its a new-style class on production. (Of course, I can't see the code, but it hasattr '__new__' and '__class__').

I'm not sure if this is a bug. It seems like you should be able to pickle app engine classes, and it would be nice if you could read that data in the SDK.

This is the exception that I get when trying to unpickle in the dev SDK:

Traceback (most recent call last):

  File "<console>", line 1, in <module>

  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.py", line 1382, in loads

    return Unpickler(file).load()

  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.py", line 858, in load

    dispatch[key](self)

  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.py", line 1083, in load_newobj

    obj = cls.__new__(cls, *args)

AttributeError: class Reference has no attribute '__new__'

--Alex

[zhao shuai]

Fell into the same trap.

    entities = query.fetch(batch_size)
  File "/home/kamel/Library/google_appengine/google/appengine/ext/db/__init__.py", line 2157, in fetch
    return list(self.run(limit=limit, offset=offset, **kwargs))
  File "/home/kamel/Library/google_appengine/google/appengine/ext/db/__init__.py", line 2326, in next
    return self.__model_class.from_entity(self.__iterator.next())
  File "/home/kamel/Library/google_appengine/google/appengine/ext/db/__init__.py", line 1435, in from_entity
    entity_values = cls._load_entity_values(entity)
  File "/home/kamel/Library/google_appengine/google/appengine/ext/db/__init__.py", line 1413, in _load_entity_values
    value = prop.make_value_from_datastore(value)
  File "/home/kamel/labola/src/model/properties.py", line 295, in make_value_from_datastore
    return pickle.loads(value)
  File "/usr/lib/python2.7/pickle.py", line 1382, in loads
    return Unpickler(file).load()
  File "/usr/lib/python2.7/pickle.py", line 858, in load
    dispatch[key](self)
  File "/usr/lib/python2.7/pickle.py", line 1083, in load_newobj

    obj = cls.__new__(cls, *args)
AttributeError: class Reference has no attribute '__new__'

在 2013年3月29日星期五UTC+9上午5时42分42秒，Alex Burgel写道：