object refresh question

[Mike Leong <leongmzlist@xxxxxxxxx>]

Hi,

I have squid setup as an accelerator to serve cgi stuff.  The cgi is pretty 
cpu intensive, takes about 20 seconds to process request, so, I have the 
requests cached as much as possible.

Problem is when to purge the cached cgi results.  The cgi does NOT have 
last modified header.

1. is it possible, when doing the HEAD command on the CGI, have it return 
the last mod date, but not execute the CPU intensive stuff.
        a. Possible complication: the content length will be 0 when doing 
HEAD. If the obj is already cached, then cached content length will be 
differ from the HEAD content length.

2. Can squid refresh object based on the folloing algo:

if (not_cached){
        retrive_it
        mark it as fresh
        set obj to expire in 7 days
        return it
}
else if (is_fresh){
        return it
}
else if (time_retrived > last_mod){
        mark the object as fresh for another 7 days (request from the next 
7 days won't bother doing last_mod check, assume it's fresh)
        return it
}


thx,
mike