Cache middleware with memcached can't handle long URLs

[Jacob]

Memcached has a hard limit of 250 characters for cache keys (​cite). However, cache keys for the cache middleware (and associated view decorators) are of the form

   'views.decorators.cache.cache_page.%s.%s.%s' % (key_prefix, request.path, headers_hash)

(​cite)

This means that if the combined length of settings.CACHE_MIDDLEWARE_KEY_PREFIX and request.path is over about 180 characters, you'll get failures. With cmemcache you get obscure server errors; the pure-Python memcached client throws MemcachedKeyLengthError.

[Timothée Peignier]

I've fix the problem by replacing request.path by an hash of request.path, see attached patch.

[Timothée Peignier]

Updated patch that generate key each form request.path everywhere it's use.

[mcroydon]

Updated patch (apply with -p1) to include tests for the new behavior.

[mcroydon]

I'm not sure if it's worth noting that this is a change in internals (we're generating a key based on a hash of the path not the path itself). There may be some people coding against the existing behavior, but they are probably firmly in "you're mucking with internals so expect things to break" territory.

I also didn't know how to best deal with the really long line lengths in the asserts so I left them there. Feel free to clean that up as you best see fit.

[mcroydon]

Working on cleaning this up a little more per Jacob.

[Jacob]

(In [10335]) Fixed #10016: the cache middleware no longer vomits when handed long URLs. Thanks, Matt Croydon.

[Jacob]

(In [10336]) [1.0.X] Fixed #10016: the cache middleware no longer vomits when handed long URLs. Thanks, Matt Croydon. Backport of r10335 from trunk.

[Jacob]

Milestone 1.1 deleted