Symfony HttpCache subscriber for custom proxy ttl

[dbu]

have a look at https://github.com/sulu-cmf/sulu/blob/develop/src/Sulu/Component/HttpCache/HttpCache.php and extract that into a subscriber, with the constant for the header as default value.

add new events to the HttpCache as needed in order to be able to do this.

[dbu]

/cc @dantleech

[stof]

@dantleech what is the reason to use a header X-Reverse-Proxy-TTL on the response instead of relying on $response->setTtl() which is setting the SharedMaxAge setting ?

[dantleech]

Passing that question to @chirimoya

[dbu]

this is an invention of the FOSHttpCacheBundle http://foshttpcachebundle.readthedocs.org/en/latest/reference/configuration/headers.html?highlight=ttl#reverse-proxy-ttl

the idea is that you control your proxy cache lifetime without killing the option to also keep a s-maxage for other proxies out in the wild. if you use s-maxage for that, you would need to unset s-maxage in the cache proxy, or you leak out that value. if you do active cache invalidation, your proxy may have high cache lifetimes - but public proxies need lower lifetimes as you don't know about them and can't invalidate there.

[chirimoya]

As @dbu already mention, if you are in control (purge, ban, ...) of a private cache it makes sense to have a different TTL as for the public caches (every proxy in between).

"If a response includes an s-maxage directive, then for a shared cache (but not for a private cache) ... " http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html

[dbu]

this is only documented and used in FOSHttpCacheBundle, not in the library. i guess the kernel subscriber should thus also go to the bundle?

[dbu]

started working on it, see #214