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Posted to dev@httpd.apache.org by Ruediger Pluem <rp...@apache.org> on 2006/01/17 14:11:44 UTC

Difference between Documentation and code for CacheMaxExpire

I found a difference between the documentation of CacheMaxExpire and the code.
The documentation of CacheMaxExpire says:

"This maximum value is enforced even if an expiry date was supplied with the document."

Looking at the code I found:

   /* if no expiry date then
     *   if lastmod
     *      expiry date = date + min((date - lastmod) * factor, maxexpire)
     *   else
     *      expire date = date + defaultexpire
     */
    if (exp == APR_DATE_BAD) {
        char expire_hdr[APR_RFC822_DATE_LEN];

        /* if lastmod == date then you get 0*conf->factor which results in
         *   an expiration time of now. This causes some problems with
         *   freshness calculations, so we choose the else path...
         */
        if ((lastmod != APR_DATE_BAD) && (lastmod < date)) {
            apr_time_t x = (apr_time_t) ((date - lastmod) * conf->factor);

            if (x > conf->maxex) {
                x = conf->maxex;
            }
            exp = date + x;
            apr_rfc822_date(expire_hdr, exp);
            apr_table_set(r->headers_out, "Expires", expire_hdr);
        }
        else {
            exp = date + conf->defex;
            apr_rfc822_date(expire_hdr, exp);
            apr_table_set(r->headers_out, "Expires", expire_hdr);
        }
    }
    info->expire = exp;

So CacheMaxExpire only applies if no valid expire date was delivered with the document.
Furthermore CacheDefaultExpire can be larger than CacheMaxExpire.

The question that remains: It this a bug in the code or in the documentation?


Regards

Rüdiger

Re: Difference between Documentation and code for CacheMaxExpire

Posted by Ruediger Pluem <rp...@apache.org>.
The issue below came up again in PR21260. So anyone with an idea now if
this is a bug in the documentation or in the code?

Regards

Rüdiger

On 01/17/2006 02:11 PM, Ruediger Pluem wrote:
> I found a difference between the documentation of CacheMaxExpire and the code.
> The documentation of CacheMaxExpire says:
> 
> "This maximum value is enforced even if an expiry date was supplied with the document."
> 
> Looking at the code I found:
> 
>    /* if no expiry date then
>      *   if lastmod
>      *      expiry date = date + min((date - lastmod) * factor, maxexpire)
>      *   else
>      *      expire date = date + defaultexpire
>      */
>     if (exp == APR_DATE_BAD) {
>         char expire_hdr[APR_RFC822_DATE_LEN];
> 
>         /* if lastmod == date then you get 0*conf->factor which results in
>          *   an expiration time of now. This causes some problems with
>          *   freshness calculations, so we choose the else path...
>          */
>         if ((lastmod != APR_DATE_BAD) && (lastmod < date)) {
>             apr_time_t x = (apr_time_t) ((date - lastmod) * conf->factor);
> 
>             if (x > conf->maxex) {
>                 x = conf->maxex;
>             }
>             exp = date + x;
>             apr_rfc822_date(expire_hdr, exp);
>             apr_table_set(r->headers_out, "Expires", expire_hdr);
>         }
>         else {
>             exp = date + conf->defex;
>             apr_rfc822_date(expire_hdr, exp);
>             apr_table_set(r->headers_out, "Expires", expire_hdr);
>         }
>     }
>     info->expire = exp;
> 
> So CacheMaxExpire only applies if no valid expire date was delivered with the document.
> Furthermore CacheDefaultExpire can be larger than CacheMaxExpire.
> 
> The question that remains: It this a bug in the code or in the documentation?
>