I'm currently using a Cache Manifest (as described here). This effectively makes the necessary resources to run the application available when the user is offline.
Unfortunately, it works a little too well.
After the cache manifest is loaded, Firefox 3.5+ caches all of the resources explicitly referenced in the cache manifest. However, if a file on the server is updated and the user tries force-refreshing the page while online (including the cache-manifest itself), Firefox will absolutely refuse to fetch anything. The application remains completely frozen at the last point it was cached. Questions:
- I want Firefox to effectively only rely on the cached resources when the network connection fails. I've tried using the FALLBACK block, but to no avail. Is this even possible?
- If #1 is not possible, is it possible for the user to force-refresh a page and bypass this cache (ctrl-F5 doesn't do it and neither does clearing the browser's cache, shockingly) short of clearing their private data? Alternatively, does the cache-manifest mechanism support expiry headers and is its behavior with respect to this documented anywhere?
Best Answer
I think I've got this figured out: if there's an error in one's cache-manifest (say, a referenced file does not exist), then Firefox completely will stop processing anything applicationCache related. Meaning, it won't update anything in your cache, including your cached cache-manifest.
To uncover that this was the issue, I borrowed some code from Mozilla and dropped this into a new (non-cached) HTML file in my application. The final message logged stated that there might be a problem in my cache-manifest, and sure enough there was (a missing file).
This was certainly helpful, but I should definitely request a feature from Mozilla that prints out malformed cache-manifests at least to the Error Console. It shouldn't require custom code to attach to these events to diagnose an issue as trivial as a renamed file.