[Zope] Image Caching

Dieter Maurer dieter@handshake.de
Wed, 12 Jun 2002 20:50:25 +0200

Smith, Neil writes:
 > I seem to remember having read something in the list before about problems
 > with caching of images, but I can't find it again.
 > Is there anything that would cause an image used multiple times on the page
 > not to be read from the cache?
 > I have a form that uses JavaScript to display itself, such that it can do a
 > sort of tabbed interface and add new lines to the form without going back to
 > the server.  This contains a  number of very small images that are
 > frequently repeated to build up the borders of the tabs etc.
 > This works well when used on the LAN, but I've now found that when used
 > across the internet, when the form redisplays itself, it takes forever to
 > build up the graphics, and you can see each individual image being slowly
 > loaded.  I'd thought it would have got the images from the cache.
There are many, many parameters that control caching.
See the HTTP/1.1 spec for details.

Maybe, you have caching disabled in your browser?

The spec tells that many responses must not be cached:

  *  responses to requests with a query string
  *  responses to post requests
  *  responses to requests that require authorization (usually not implemented)
  *  responses with corresponding cache control headers
  *  responses lacking a "Modified" and "Etag" header
  *  ....

difficult to tell what case prevents caching for you.