Max-age and 304 Not Modified Processing

问题:

I've been looking at the standards - but was not entirely sure about the following:

If we have a variant (resource, image, page etc) that is served with a cache setting of max-age=259200 (3 days) and the server is also processing ETags and last modified dates - then what will happen when the max-age is reached - but the resource has not been modified?

What I'm hoping will happen is that after 3 days - the client will request the resource again - and if it has not changed will received a 304 Not Modified response. If the cache control response (during the 304 response) also still contains max-age=259200 - then I'm hoping the client will continue to use its local cached copy and not request again for another 3 days.

What I'm afraid will happen is that once the max-age is reached - the client will no longer cache the resource - making a fresh request each time the resource is loaded - followed by a 304 Not Modified response if the resource has not been modified. i.e. we're now getting http requests for every use as opposed to using the local cache for another 3 days.

Thoughts?

回答1:

It will cache for 3 more days. RFC 2616 10.3.5:

If a cache uses a received 304 response to update a cache entry, the cache MUST update the entry to reflect any new field values given in the response.

Details about age calculation.