You can use the marathon-lb-autoscale application to implement request rate-based autoscaling with Marathon. The marathon-lb-autoscale application works with any application that uses TCP traffic and can be routed through HAProxy.
marathon-lb-autoscale collects data from all HAProxy instances to determine the current RPS (requests per second) for your apps. The autoscale controller then attempts to maintain a defined target number of requests per second per service instance. marathon-lb-autoscale makes API calls to Marathon to scale the app.
For more information, see the Marathon-LB advanced features documentation.