Re: How squid caches some things

On Mon, 17 Oct 2005, Evgeny Kotsuba wrote:

> d) ignore-reload, if a cached copy is found, verifying that our cached
> copy is up to date but and ignoring "Pragma: no-cache" in tis case
> only .

How is this different from reload-into-ims?

Reload-into-ims changes the "Pragma: no-cache" into a forced cache
revalidation only, forcing the cache to verify that it's cached copy is up
to date.

> This seems to be a common thing - to set Pragma: no-cache to static
> objects like images

Important note: Don't mix up request and response headers. The two are
very different things.

> And what RFC sais about specially/erroneosly/ maliciously "Pragma:
> no-cache" ?

There is no such thing in an RFC.

If a client says "Pragma: no-cache" in it's request header it is supposed
to be knowing why it is doing so. And it can by definition not be declared
malicious as all it does is to degrade the system to uncached operation.

There is no official "Pragma: no-cache" response header whereby servers
can say responses are not cacheable, but many do and Squid honors this.
Again, not malicious but maybe a careless thing to do by the server..

The RFCs is very clear that if a client or server wants to force uncached
processing then it is entirely in it's right to do so. Caching
friendlyness in HTTP is optional, not mandatory.

Regards
Henrik
Received on Mon Oct 17 2005 - 17:01:48 MDT