Google appengine blobstore debugging

Question

I'm having an issue with blobstore uploads, but because of the way gae handles all of that, actually figuring out what the error was is giving me some trouble. I'm using django, which unfortunately tries very hard to prevent exceptions from reaching the user without formatting. It looks like the uploads are successful, there are __BlobInfo__ entities in the database, but then something is happening thats causing a 500 response.

Here's what the log says:

INFO     2010-09-29 03:54:33,236 dev_appserver.py:529] Internal redirection to /img/imup/aglwaGFzZS10d29yDQsSB1Byb2plY3QYAgw
INFO     2010-09-29 03:54:33,654 dev_appserver_blobstore.py:328] Upload handler returned 500
ERROR    2010-09-29 03:54:33,654 dev_appserver_blobstore.py:341] Invalid upload handler response. Only 301, 302 and 303 statuses are permitted and it may not have a content body.
INFO     2010-09-29 03:54:33,736 dev_appserver.py:3275] "POST /_ah/upload/aglwaGFzZS10d29yGwsSFV9fQmxvYlVwbG9hZFNlc3Npb25fXxgPDA HTTP/1.1" 500 -

Is there some way to get more useful debug information out of the SDK?

Answer 1

Well, here's how i'm now making progress. It's kind of icky:

try:
    # something that might not work
except Exception, e:
    return http.httpResponseRedirect('/%s'%repr(e))

and then I can read the error that occured in the URL.

I hope I can accept someone elses (much better) answer, because this is a terrible hack and it's no fun!

Answer 2

The exception your code is raising should be output immediately above the log lines you pasted - scroll up! If it's not, something in your framework is catching exceptions and not reporting them - possibly it's returning them to the user, which is not much use in this scenario.