Cache middleware description

[anonymous]

Original text:
Order of MIDDLEWARE_CLASSES

If you use CacheMiddleware, it’s important to put it in the right place within the MIDDLEWARE_CLASSES setting, because the cache middleware needs to know which headers by which to vary the cache storage. Middleware always adds something to the Vary response header when it can.

Put the CacheMiddleware after any middlewares that might add something to the Vary header. The following middlewares do so:
SessionMiddleware adds Cookie
GZipMiddleware adds Accept-Encoding

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First, the list lacks LocaleMiddleware as it adds vary Accept-Language.
Second, the responce is handled by middleware in reverse order, hence CacheMiddle must be placed BEFORE any middleware that change vary header.

[Malcolm Tredinnick]

Fixed in [6575], although I typed the wrong ticket number in the commit message.