[spook-l] Refreshing JPEG snapshots

[Vladimir Lasky]

> When I get back from OLS I need to check on this, but browsers definitely 
> should not be caching the JPEG snapshot.  I'll try to figure out what's 
> missing from the headers that cause this.

I read a tutorial on caching (http://www.mnot.net/cache_docs/) to understand the
headers and their options. Based on that, Spook's headers appear to cover all
bases (HTTP 1.0 and 1.1). Once I put the Date header code in, the cacheability
testing tool gave it the all clear.

Other headers that may be worth exploring are 'Cache-Control: no-store' and the
'Last-modified' and ETag validators.

Still, I believe that the problem is in Mozilla and Firefox (Firefox is a
derivative of Mozilla right?) - perhaps it is trying to be clever by avoiding
what it deems to be unnecessary inline image updates from Javascript as most of
the time these do not change. When you refresh the page manually, the image is
updated.

Assuming this bug is confirmed and rectified, there will still be a large
installed base of browsers that have it. For this reason, I recommend that the
query string method should be supported.

IE also appears to update the image faster, perhaps because it skips checking to
see if the page has a new version, though 'Cache-control: no-store' should
avoid that - I stopped testing headers once I implemented the query string
method.


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