bug in wsgi handler in trunk

[Waldemar Kornewald]

I get the following traceback with Django trunk:

...
  File "...\django\core\handlers\wsgi.py", line 251, in __call__
    request = self.request_class(environ)
  File "...\django\core\handlers\wsgi.py", line 137, in __init__
    if isinstance(self.environ['wsgi.input'], socket._fileobject):
TypeError: isinstance() arg 2 must be a class, type, or tuple of classes and types

When I changed the isinstance check to use .__class__ it worked, again.

[Russell Keith-Magee]

I don't see this error under the Django devserver, mod_wsgi, or the CherryPy devserver.

I'm going to guess this is happening on AppEngine?

[Waldemar Kornewald]

Yes, you're right. I can only reproduce it on App Engine. Looks like they do something non-standard here.

[Russell Keith-Magee]

Ok - in which case, you'll have to provide a patch that you can verify works. I don't have easy access to testing for AppEngine.

As a side note, I'd be interested to know what datatype socket._fileobject *is*, if it isn't a class or type.

[Waldemar Kornewald]

Their servers and SDK emulate _fileobject as a function instead of a class. :(

If I understand the check correctly it's purpose is to check if we're running the development server, right? Is there some alternative method to do this cleanly?

[Russell Keith-Magee]

You've understood the purpose of the check correctly; I can't think of an obvious alternative, other than providing a subclass of WSGIRequest that is used by the dev server and nothing else. Suggestions welcome.

[Waldemar Kornewald]

As an alternative, the following patch makes it work on App Engine:

diff -r d45c568421e5 django/core/handlers/wsgi.py
--- a/django/core/handlers/wsgi.py      Tue Nov 02 13:58:12 2010 +0100
+++ b/django/core/handlers/wsgi.py      Tue Nov 02 14:57:24 2010 +0100
@@ -134,7 +134,8 @@
         self.META['SCRIPT_NAME'] = script_name
         self.method = environ['REQUEST_METHOD'].upper()
         self._post_parse_error = False
-        if isinstance(self.environ['wsgi.input'], socket._fileobject):
+        if type(socket._fileobject) is type and \
+                isinstance(self.environ['wsgi.input'], socket._fileobject):
             # Under development server 'wsgi.input' is an instance of
             # socket._fileobject which hangs indefinitely on reading bytes past
             # available count. To prevent this it's wrapped in LimitedStream

But this is just a workaround. Is this OK or should I try to fix this a custom WSGIHandler that has a custom WSGIRequest? Could that result in incompatibility issues with 3rd-party runserver alternatives? I'm not really familiar with this part of Django's code.

[Russell Keith-Magee]

I suspect that this is more an issue with AppEngines curious sandbox implementation of the python standard library than with the WSGI wrapper itself. To that end, I'm happy to treat this as a workaround. Fix incoming.

[Russell Keith-Magee]

(In [14453]) Fixed #14602 -- Added an extra check to wsgi.input handling to prevent AppEngine from choking. Thanks to Waldemar Kornewald for the report.

[Waldemar Kornewald]

Thanks a lot!

[Jacob]

Milestone 1.3 deleted