ProxyPass /forum balancer://forumcluster
ProxyPassReverse /forum balancer://forumcluster

<Proxy balancer://forumcluster>
  BalancerMember http://127.0.0.1:3000/forum
  BalancerMember http://127.0.0.1:3001/forum
  BalancerMember http://127.0.0.1:3002/forum
  BalancerMember http://127.0.0.1:3003/forum
  Order deny,allow
  Allow from all
</Proxy>