Re: [squid-users] max-age and Last-Modified header

ons 2006-11-29 klockan 15:09 -0800 skrev Mohan:

> We are seeing if Squid supports ETag based revalidation of highly
> dynamic content in a reverse proxy cache configuration.

It does support fairly advanced use of Vary and ETag.

The weak sides is that it does not fully follow the cache invalidation
rules.

> We cannot use time based caching (Last-Modified and max-age headers)
> because of the "resource representation" -- same resource (page) but
> different representation (the HTML). There are two different types of
> users. Readers vs Posters. 99% of the users are Readers and will see the
> same page but the page is represented differently for the 1% of the
> users who are actually Posters.

Thats the job of Vary.

> 1. Squid doesnot cache the page if the response does not include a
> Last-Modified or a max-age (with a value greater than 0) header.

Hmm.. the logics in 2.6 is meant to account for ETag as well, but seems
that got lost somewhere..

> Note : We can't return Last-Modified: because it tickles IE6 caching
> bugs. We can't add a max-age>0 for shared caches because the content
> may (1% of the time) be different for different users as described above.

Well.. Vary?

If you don't Vary then HTTP specifies there is only a single response
for the URL, and any new response MUST replace the earlier ones...

Regards
Henrik