Apache Websocket Proxy (socket.io) with Load Balancing

default.conf

<VirtualHost *.:443>

  ServerName whatever-domain.com

  ErrorLog ${APACHE_LOG_DIR}/error.log
  CustomLog ${APACHE_LOG_DIR}/access.log combined

  SSLProxyEngine on
  ProxyPreserveHost on
  RewriteEngine On

  Header add Set-Cookie "ROUTEID=.%{BALANCER_WORKER_ROUTE}e; path=/" env=BALANCER_ROUTE_CHANGED
  <Proxy "balancer://martin-cluster/" timeout=10 failontimeout=on>

    RequestHeader set X-Forwarded-Proto "https"

    BalancerMember "http://192.168.1.2:8080" route=1 ttl=5 ping=500ms loadfactor=1 retry=3
    BalancerMember "http://external-domain.com" route=3 ttl=5 ping=500ms loadfactor=1 retry=3 status=+H

    ProxySet lbmethod=byrequests
    Order deny,allow
    Allow from all
  </Proxy>

  <Proxy "balancer://martin-cluster-ws/" timeout=10 failontimeout=on>
    BalancerMember "ws://192.168.1.2:8080" route=1 ttl=5 ping=500ms loadfactor=1 retry=3
    BalancerMember "ws://external-domain.com" route=3 ttl=5 ping=500ms loadfactor=1 retry=3 status=+H

    ProxySet lbmethod=byrequests
    Order deny,allow
    Allow from all
  </Proxy>

  <Proxy *>
    Order deny,allow
    Allow from all
  </Proxy>

  RewriteCond %{REQUEST_URI}  ^/socket.io            [NC]
  RewriteCond %{QUERY_STRING} transport=websocket    [NC]
  RewriteRule /(.*)       balancer://martin-cluster-ws/$1 [P,L]

  ProxyPass "/" "balancer://martin-cluster/"
  ProxyPass "/socket.io/" "balancer://martin-cluster-ws/socket.io"
  ProxyPassReverse "/socket.io/" "balancer://martin-cluster-ws/socket.io"

</VirtualHost>