Deploying application via Ansible playbook without bringing both sides down

I'm using Ansible to deploy a Java web application. Deployment is quiet basic via Ansible running a Jenkins playbook, copying a jar-file to 2 separate application servers, called node-01a and node-01b, both behind an Amazon AWS load balancer.

Currently the deployment happens on both the node-01a and node-01b at the same time. What would be the easiest way to do this without both nodes going down at the same time?