Marathon-LB is a tool for managing HAProxy that works by consuming Marathon's app state. HAProxy is a fast, efficient, battle-tested, highly available load balancer with many advanced features that power a number of high-profile websites. Marathon-LB provides a Python script that performs zero-downtime applications deployments. It helps you to safely deploy applications serving live traffic by creating two versions of an application: blue and green.

Let's see how it is done:

1. To perform an application update, the green version is deployed, while all customer requests are sent to the blue version.
2. Once the green version is deployed and healthy, the load balancer can start draining connections from the blue version and instead sends customer requests to the green version.
3. The blue version of the application can be deleted once all customer requests are being...