Failure cenarios?

[Gaute Amundsen]

I have come to understand that in some builds under some conditions varnish 
may hang or a crash. (we run 1.0.4-3el4.i386.rpm)

I have now routed all our ~180 sites troug varnish, pipe by default, cached 
for selected hostnames. Talk a bout all ones eggs in one basket :)

The way it is all set up, we have varnsih on port 80 on one IP and apache on 
80 on another whch is not in use for anything directly.
If anything should hapen to varnish, or we need to upgrade or anything, 3 
lines to netfilter wil reroute all the trafic directly to apache.

Now the question is, how do I best detect if varnsih should have a problem?
Would it be reasonably reliable to just chek if the pid 
from /var/run/varnish.pid is running, do I need to fetch a page, or is there 
some better way?

Gaute