Which reverse-proxies support HTTP/1.1 ETag and If-None-Match headers?

ColinM asked:

I’m developing a caching system for an ecommerce platform that will use a reverse proxy for caching. I plan to handle invalidation by using proper HTTP/1.1 headers. That is, I will set an ETag on first generation of the content and cache that ETag value in the application. The Cache-Control header will specify “must-revalidate” so the proxy should set If-None-Match header on subsequent requests with the ETag. The application will lookup the cached ETag value and if it matches it will send a 304 response, otherwise it will generate a full 200 response.

I hoped to use nginx but I can’t tell for sure that it supports ETags (docs indicate it doesn’t but maybe they are out of date?). Varnish is another option but I’m not positive here either..

Which reverse proxy servers out there have full support for ETags? I’d like it to actually cache multiple versions so I can do things like split testing without having to disable the cache. That is, HTTP/1.1 specifies that a client can send If-None-Match with multiple ETag values and the server should respond with which ETag matched (if any). If the reverse proxy kept multiple copies rather than just the last-seen value and let the server specify on each request which to use, that would be ideal.

My answer:

nginx requires third party modules to support ETag. And there are two of them.

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