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From CASTELLE Thomas <>
Subject [PATCH] mod_cache RFC compliance
Date Thu, 12 Jun 2003 15:49:02 GMT

In order to accelerate the RFC compliance of mod_cache, I propose these two
patches which fix two problems :
- It doesn't handle the Cache-Control directives (max-age, max-stale,
min-fresh...) properly.
- It doesn't send a "If-Modified-Since" to avoid that the backend server
sends every time a 200 response where a 304 would be enough.

Actually, we are waiting for these features to be implemented since
http-2.0.43 so that we could put Apache in our production environment. I am
not an Apache developper, so this is just a proposition, but I tested it and
it seemed to work.

The cache_util.c patch deals with the first issue. First, the Cache-Control
directive seems to be in the r->err_headers_out and not in the
r->headers_out. Second, the following test seems useless :

	if ((-1 < smaxage && age < (smaxage - minfresh)) ||
          (-1 < maxage && age < (maxage + maxstale - minfresh)) ||
          (info->expire != APR_DATE_BAD &&
           age < (apr_time_sec(info->expire - info->date) + maxstale -
minfresh))) {

because it is always true, no matter if max-age is set or not. 
Let's take an example (I suppose here s-maxage, max-stale and min-fresh not
so smaxage = - 1, maxstale = 0 and minfresh = 0) :
- with age = 20, maxage = -1 (not set) and expire - date = 30, the second
is FALSE. The third is TRUE. So the whole test is TRUE, the page is
to be fresh => no problem.
- with age = 20, maxage = 10 and expire - date = 30, the second test is
but the third is still TRUE. So the whole test is TRUE, the page is
to be fresh => problem.

The mod_cache.c patch deals with the second issue. The info structure is
never initialized, and even if it was, the info->lastmods and info->etag
don't seem to be saved in the file when using mod_disk_cache. So I used the
Etag and Last-Modified informations we can find in the r->headers_out and
r->err_headers_out. I don't know if it's correct, but it seems to work

Thanks for looking to these patch and eventually integrate it in the next
Apache release !

Thanks a lot for this really great product !


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