Joe Ludwig Joe Ludwig - 3 months ago 14
Python Question

AppEngine BlobStore upload failing with a request that works in the Development Environment

I have an AppEngine application that uses the blobstore to store user-provided image data. When I upload images to that application from a form in Chrome it works fine. When I try to upload an image from an Android application it fails. Both methods work fine if I am running against the development server, but the Android upload doesn't work against the live service.

This is the request from Chrome:

POST /_ah/upload/?userToken=11001/AMmfu6ZCyMQQ9YdiXal3SmSXIRTQIuSRXkNc-i3JmU0fqx_kJbUJ2OMLcS2lXhVJSK4qs7regViTKzOPz5ejoZYi0nAD5o8vNltiOViQw6DZO7_byZz3Ut0/ALBNUaYAAAAAS_lusgPMAGmpPrg0BuNsJyymX-57ob4i/ HTTP/1.1
Host: photohuntservice.appspot.com
Connection: keep-alive
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US) AppleWebKit/532.5 (KHTML, like Gecko) Chrome/4.1.249.1064 Safari/532.5
Referer: http://photohuntservice.appspot.com/debug_newpuzzle?userToken=11001
Content-Length: 60360
Cache-Control: max-age=0
Origin: http://photohuntservice.appspot.com
Content-Type: multipart/form-data; boundary=----WebKitFormBoundarybl05YLmLbFRf2MzN
Accept: application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
Accept-Encoding: gzip,deflate,sdch
Accept-Language: en-US,en;q=0.8
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3

------WebKitFormBoundarybl05YLmLbFRf2MzN
Content-Disposition: form-data; name="userToken"

11001
------WebKitFormBoundarybl05YLmLbFRf2MzN
Content-Disposition: form-data; name="img"; filename="Photo_020908_001.jpg"
Content-Type: image/jpeg

<image data>
------WebKitFormBoundarybl05YLmLbFRf2MzN
Content-Disposition: form-data; name="longitude"

-122.084095
------WebKitFormBoundarybl05YLmLbFRf2MzN
Content-Disposition: form-data; name="latitude"

37.422006
------WebKitFormBoundarybl05YLmLbFRf2MzN--


This is the request from my client (which is written in Java on Android, but I don't think that's relevant):

POST /_ah/upload/?userToken=11001/AMmfu6Zf9an6AU4lT9UuhIpxOZyOYb1LMwimFpeSh8zr6J1sX9F2ddJW3Qlsw0kwV3oALv-TNPWRQ6g4_Dgwk0UTwF47bbc78Yl44kDeV69MydTuR3N46S4/ALBNUaYAAAAAS_mMr3CYqTg3aVBDjhRxP0DyyRdvotyG/ HTTP/1.1
Content-Type: multipart/form-data;boundary=----WebKitFormBoundaryhdyNAhmOouRDGErG
Cache-Control: max-age=0
Accept: */*
Origin: http://photohuntservice.appspot.com
Connection: keep-alive
Referer: http://photohuntservice.appspot.com/getuploadurl?userToken=11001
Content-Length: 2638
Host: photohuntservice.appspot.com
User-Agent: Apache-HttpClient/UNAVAILABLE (java 1.4)
Expect: 100-Continue

------WebKitFormBoundaryhdyNAhmOouRDGErG
Content-Disposition: form-data; name="userToken"

11001
------WebKitFormBoundaryhdyNAhmOouRDGErG
Content-Disposition: form-data; name="img";filename="PhotoHunt.jpg"
Content-Type: image/jpeg

<image data>
------WebKitFormBoundaryhdyNAhmOouRDGErG
Content-Disposition: form-data; name="latitude"

37.422006
------WebKitFormBoundaryhdyNAhmOouRDGErG
Content-Disposition: form-data; name="longitude"

-122.084095
------WebKitFormBoundaryhdyNAhmOouRDGErG--


In both cases the AppEngine Python code to catch the request is the same:

class UploadPuzzle( blobstore_handlers.BlobstoreUploadHandler ):
def post(self):
upload_files = self.get_uploads( )


The problem is that when running on the production AppEngine service self.get_uploads() returns an empty list when the request is made from my client app. Both requests return what I expect (a list with one blob_info in it) on the development server, and Chrome returns what I expect in both cases.

Answer

Turns out the problem was this line:

Content-Disposition: form-data; name="img";filename="PhotoHunt.jpg"

It should read like this:

Content-Disposition: form-data; name="img"; filename="PhotoHunt.jpg"

The parser for form-data on the production servers is more strict than the one in the development environment and requires a space between the semicolon and "filename="