Make a scalable application HA

First follow these to allow multiple HAProxies on a Node Host

1. Open the /etc/openshift/broker.conf file on the broker host and set the
    ALLOW_MULTIPLE_HAPROXY_ON_NODE value to true:

    ALLOW_MULTIPLE_HAPROXY_ON_NODE="true"

2. Restart the openshift-broker service:

     service openshift-broker restart

3. Run the following command to make a scalable application HA
  
     rhc app-create your-app-name cartridge-name  -s  -x 
        OR
    rhc app-create your-app-name cartidge-name -s --make-ha

4. Check if you have 2 HA-proxies on each of the 2 gears created by running the following command-
    
    rhc app-show your app name --gears

You need to specify a default value for the `available` parameter (`available=nil`) to make it an optional parameter because it follows other optional parameters.