In this example, we will perform a blue/green deployment technique using the zdd.py Python script and special Marathon-LB labels in your application definitions.
You need to first install Marathon-LB, using a Docker image, by executing the following command:
docker run -d -p 9090:9090
As you can see in the preceding command, 9090 is the port to which your HAProxy will bind–you access the HAProxy web page to find out the status of your load balancer. Then, next is -p 8081:10001. This is where your services will run. Here, we set it to 10000 and 8081. So, we have exposed the 8081 port where your application will get accessed; and inside Docker, 10000 will be used. So, this is how your port mapping will happen. After that, we defined --add-host.
This variable needs to be defined if you don't have any DNS. If you have DNS in your environment, you...