vcl newbie question

[Fred Clift]

I'm going to have many domains being proxied by varnish and I'd like
to be able to invalidate by doing a PURGE on a different IP than the
domain...

At system startup, and as an emergency tool for system administrators,
I BAN entire domains.


For my whole-domain BANs my vcl looks like:

        # allow HOSTBAN from localhost and hosts in purge acl
        # HOSTBAN covers entire domain
        if (req.request == "HOSTBAN") {
                # Same ACL check as above:
                if (!client.ip ~ purge) {
                        error 405 "Not allowed.";
                }
                std.log("trying to ban " + req.url);
                ban("req.http.host == " + req.url);

                # Throw a synthetic page so the
                # request won't go to the backend.
                error 200 "Ban added";
        }



and my python code does the following:


def do_hostban(cachehost, domain):
    conn = httplib.HTTPConnection(cachehost)
    conn.request("HOSTBAN", domain)
    rl = conn.getresponse()
    conn.close()
    debugprint( "%s %s" % (rl.status, rl.reason))
    return rl.status, rl.reason

do_hostban("cacheIP", "www.bandomain.com")

This does approximately the same as you can with curl, without all
that nasty shell interpolation:

/usr/bin/curl -s -X HOSTBAN "http://cacheIP/www.bandomain.com"

I'd like to keep the cache host/ip separate from the domain(s) being
hosted so that I could proxy or aggregate these at some central point
(from several servers) without having to change much.




So, my real problem is that I really only have a very superficial
understanding of vcl.  for purges I have:

sub vcl_recv {
        # allow PURGE from localhost and hosts in purge acl
        # PURGE does a single, unique URL (+Vary-iants)
        if (req.request == "PURGE") {
                if (!client.ip ~ purge) {
                        error 405 "Not allowed.";
                }
                return (lookup);
        }
}


sub vcl_hit {
        if (req.request == "PURGE") {
                purge;
                error 200 "Purged.";
        }
}

sub vcl_miss {
        if (req.request == "PURGE") {
                purge;
                error 200 "Purged.";
        }
}



How would I modify this code so that I could purge via approximately
the following syntax?

http://varnishIP/www.purgedomain.com/some/url.php


I've stared at the docs for a while, and ended up going back t work on
other parts of my project while hoping for enlightenment.


Fred