id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
17834	ETag generated from empty content can break http caching	Paul Egan	nobody	"The [source:/django/trunk/django/utils/cache.py?rev=17286#L100 patch_response_headers] function will set an ETag header using an md5 hash of the response content.  Many responses like redirects can have an empty body and this results in the same ETag for each such response.  The response headers may vary but an intermediate cache can serve an incorrect response because the ETag is not unique.

A simple solution is to not set ETag if the content is empty - see attached patch.

{{{#!python
>>> from django.http import HttpResponseRedirect
>>> from django.utils.cache import patch_response_headers
>>> r1 = HttpResponseRedirect('/u1')
>>> patch_response_headers(r1)
>>> r2 = HttpResponseRedirect('/u2')
>>> patch_response_headers(r2)
>>> r1['ETag'] == r2['ETag']
True
}}}"	Bug	closed	HTTP handling	1.3	Normal	fixed		rene.puls@… k@…	Accepted	1	0	1	0	0	0