sticky conn and health check

[Cherife Li]

Hi all.
Varnish is such a wonderful accelerator that I want to say thanks to the 
Varnish project and all its contributors.

We're using Varnish 1.1.2 in production environment.
Recently we've got two problems, no solutions found even if searched the 
web or checked the man pages.

One is sticky connection.
The problem is how can varnish send request to the same backend when it 
receives a request it processed before.
For example,
   GET http://foo.com/a.gif
how can Varnish pass the request to the *same* backend when it receives 
this request? (if we don't cache the request)
Is there a way to do URI hash? Or any other methods?

The other one is health check.
Can Varnish do health check? So that when it treats a backend as down, 
Varnish won't send requests to it any more until Varnish sees it up again.
I don't know if heartbeat form High Availability Linux project combines 
Varnish could do health check.

Any suggestions?
Thanks all.
--
Rgds,
Cherife.