Apache – proxy: No protocol handler was valid for the URL /. If you are using a DSO version of mod_proxy

So it took some time but I figured out the way to do it. There is one more module which needs to be loaded. This is what the httpd.conf looks like

LoadModule proxy_module modules/mod_proxy.so
LoadModule proxy_http_module modules/mod_proxy_http.so

<Directory />
    AllowOverride none
    Require all denied
</Directory>

ProxyPass         /ROOT  http://localhost:8080/ROOT
ProxyPassReverse  /ROOT  http://localhost:8080/ROOT

This works for sure. :)

This can happen if you don't have mod_proxy_http enabled

sudo a2enmod proxy_http

For me to get my https based load balancer working, i had to enable the following:

sudo a2enmod ssl
sudo a2enmod proxy
sudo a2enmod proxy_balancer
sudo a2enmod proxy_http