http://wiki.codemongers.com/NginxHttpUpstreamModule

IP hash based distribution is probably what you want

On 6/28/08, Jeff Peng <peng.kyo@(protected):
> Hello,
>
> We have some modperl application servers.
> Follow the suggestion on this list, I will use a nginx in front of
> them to do the load balance.
> But I have a question, does nginx support for session-keeping?
> A user's request, should go always to the same original backend server.
> Otherwise the user's session will get lost.
>
> Thanks!
>
> --
> Regards,
> Jeff. - Peng.Kyo@(protected)
>