Hello,

Here is a very simple patch to add some env vars to mod_proxy_balancer.  This
allows you to figure out where the request was routed from the reverse proxy.  I
needed this to add sticky session cookies to the response because I could not
modify the backend app.

So, you can do something like this on the reverse proxy:

SetEnvIf ^Cookie$ "MYCOOKIE=([^ ;]*)" MYCOOKIE=$1
Header append Set-Cookie "MYCOOKIE=%{UNIQUE_ID}e.%{BALANCER_WORKER_ROUTE}e;
path=/" env=!MYCOOKIE

RewriteRule ^/+(.*) balancer://test/$1 [P]
ProxyPassReverse / balancer://test/

<Proxy balancer://test>
  BalancerMember http://host1 route=host1
  BalancerMember http://host2 route=host2
</Proxy>
ProxySet balancer://test stickysession=MYCOOKIE nofailover=On