Re: cache cluster

Henrik Nordstrom wrote:
>
> Ronald Warner wrote:
>
> > each other don't download the newest object from their sibling
> > caches, they simply get them from the one that responds fastest.
> > You should use the cachemgr.cgi script to clear the objects from
> > each and every cache, one by one."
> >
> > Is this still true for the the newer versions of squid?
>
> Yes. It is not an issue with Squid, but with having multiple caches. If
> you force one to be updated does not necessarily mean that the other
> will be. The other might still contain an stale or corrupt version of
> the object.
>

You can use a proxy.pac to balance requests between your 2 proxies; see
http://naragw.sharp.co.jp/sps/index.html

However, we still have the problem with a proxies hierarchy (unless using ICP) :
AFAIK a child with 2 parents will use the first declared parent, or will use a
round robin function.
NetCache (from Network Appliance) has a special hierarchy feature for this issue
: every child proxy use a hash table to always choose the right parent depending
on the url. Therefore objects are not duplicated among parent caches.

At last, writing a script (or a CGI) to clear an object from every cache is easy
: for each proxy /local/bin/client -m PURGE -h $proxy_ip -p $proxy_port $url

Charles Bruneteau
Received on Wed Jun 14 2000 - 09:15:38 MDT