image caching. Loading only new images

[Peregrin]

we develop huge game and it takes some time to load on startup because of tons of assets. Once per week or 2 weeks it is updated to new version which might bring few new assets or update previous ones.
So now we are trying to find the way that will allow flash to load only new/updated assets and the rest to fetch from cache. But we haven't succeeded yet. Does anybody have any idea?

[toli]

It should "fetch it from cache" automatically, as long as the url for the image is the same and its headers have not changed.
Question is - can you verify that those images are in cache?

[Peregrin]

The application doesn't need to know if the image is in cache. Instead it needs the way to distinguish whether an image is new/updated and if so to load it from remote storage (using timestamp, for instance).
So the global goal is make the application capable of refreshing only those images that are new/updated. It will prevent asking user to clear cache as well as displaying old images that have been updated.

[toli]

i understand that the app doesnt need to know what images are cached - the browser takes care of that on its own - if you request to load an image that's cached by the browser, it won't actually load it from URL - it would load it from cache. thus the question is - how do you know that the browser still has those images in cache and it hasn't gotten rid of them?

[henke37]

You can't know. And you can't know if there are any other caches involved. There may be proxy servers on the way. Some may be on the client side, some may be on the server side and not all of them may be obvious.

[Peregrin]

guys, you took me wrong. I don't care about whether an image is in cache. Rough example:
assume the cache is clear, now application started and downloads images 1 and 2 from a storage, if the page is refreshed those 1 and 2 images will be fetched from cache. Now new version of game is coming and the 2 image is updated and 3 image is added. The 3 image is not in cache so it's downloaded automatically from storage but the 2 image is IN cache and will be fetched from there by normal loading unless a timestamp is used for example. So I need to make sure the updated images will NOT be taken from cache.
How to figure it out? Using a proper timestamp? By images renaming? Sending to client the list of updated images?

[henke37]

I recommend using a compromise between letting caching work and using a cachebuster. Use a version unique url. It will ensure that caches can't cache a stale copy, but that they can still cache the latest version.