Re: Question

On Thu, 18 Sep 1997, Mario L. Peralta wrote:

> Could somebody help me with this?
> Squid 1.1.10 aparently replaced an image in the cache for other image.
> Accessing the an html page using our proxy server (squid 1.1.10)
> shows a different image than accessing the same page not using the
> proxy server.
> I've removed the wrong image from the cache directory and the problem
> dissapeared.
> Why squid did such a thing?

The Jerusalem Post does this with images and articles, because of the way
their newspaper-to-web converter software works. All the filenames
stay the same, just the content changes.

For the most part, images are considered by the cache and other software
to be fairly static -- that if the file has the same name, it will
probably have the same contents, and so it doesn't need to check to see if
the file has been updated very often. For instance, you wouldn't want to
check every 10 minutes to see if the Netscape logo JPG has changed, would
you?

The same image update problem would happen if you started up Netscape with
"Once Per Session" checking set, got the image, and then changed the file
on the server without restarting Netscape. When you removed the image,
Squid retrieved the fresh copy and put it in the cache.

In order to override this, the web server should set an expiration time on
the image file to either the current time, or to around the time when the
image is expected to change. In the case of the Jerusalem Post, they
should set the expiration of the image files to a couple of hours before
the change usually takes place.

This is done using metafiles accessed by the Web server software.

        -Mike Pelletier.
Received on Thu Sep 18 1997 - 10:45:18 MDT