To make the directive more useful I suggest the attached patches. The first one will make the directive use balancer ids to look up matching worker names instead of just dumping the balancer name into the cookie - which is obviously never useful at all.
The second one will default an empty second argument to the hostname of the client request so the cookies get reverse mapped to the correct domain, in case the client can reach the reverse proxy on multiple domains.
1_balancer_argument_for_reverse_cookie_domain.patch
Description: Binary data
2_default_argument_cookie_domain.patch
Description: Binary data
