Intelligent/automatic cache expiry based on mtime

["Jergen Dutch" <jergendutch@xxxxxxxxx>]

Hi list,

I have an application that loads a lot of images off a server every 60 seconds. I want the client's browser to cache the images because they almost never change.

In the rare cases where an image does change, I would like to invalidate the client's cached copy of the image.

I could do this with a script, but it seems such a simple and generic thing that Apache must surely already provide this (I can't find it though).

Can I add a cache-invalidation header for .jpg files modified in the past 120 seconds?

Thanks.