mod_expires/5728: Expiring CGI forms after 'Back' button is pressed

[Ali Hussein <al...@wcn.co.uk>]

>Number:         5728
>Category:       mod_expires
>Synopsis:       Expiring CGI forms after 'Back' button is pressed
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    apache
>State:          open
>Class:          sw-bug
>Submitter-Id:   apache
>Arrival-Date:   Wed Feb 09 12:10:00 PST 2000
>Closed-Date:
>Last-Modified:
>Originator:     al@wcn.co.uk
>Release:        1.3.4
>Organization:
apache
>Environment:
SuSE Linux 6.1 (kernel 2.2.5), Apache 1.3.4 with built-in mod_perl/1.18 and PHP/3.0.7, installed from binary distribution
The output of 'uname -a' is:

Linux epic3 2.2.5 #6 SMP Wed Aug 11 17:45:52 GMT 1999 i686 unknown
>Description:
Okay, we've setup caching on our system using mod_expires, setting the expire
time at 0 seconds. We did this to stop certain proxy servers from caching CGI
scripts, which was very annoying. Anyhow, it all worked perfectly, apart from the
fact that whereas before we used to be able to press the back button and have
a CGI form / serch results page showing exactly what it showed before without
reloading, now our browser has to reload every single page when the back button
is pushed. Is there any way to overcome this problem? We really need to expire
pages so that everyone can see our pages without having to press reload, though 
obviously we also don't want people to re-input all their details into any form
before doing a search.
>How-To-Repeat:
If you go to the site http://huxley.wcn.co.uk, and click on say 'Vacancies' on
the side menu, you will get a search form. Put in completely random items here,
and then click 'Search'. When you eventually receive the results, either:

i) click on the 'Back' button, in which case the form will be reloaded completely
and consequently re-initialised, or,
ii) if there are any results (try searching on UK to get any results), then click
on 'View' for a particular vacancy, and when it shows, click 'Back' and you get
a 'Data Missing' error, and so you have to reload the page
>Fix:
Well, the only thing I can think of is to doing the caching on a page by page basis,
though that still leaves us the problem of what if I update data on a CGI
page (through a database say), then the people on the proxy server will still
use the cached version, which will cause problems. Other than this, no.
>Release-Note:
>Audit-Trail:
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