Chapter 5. Red Hat OpenShift installation planning and considerations 93
OpenShift-Ansible
Ansible is a simple IT automation engine that automates cloud provisioning, configuration 
management, application deployment, intra-service orchestration, and many other IT needs.
Ansible uses no agents and no other custom security infrastructure, so it is easy to deploy 
and most importantly, it uses a simple language (YAML, in the form of Ansible Playbooks) with 
which you can describe your automation jobs in a way that approaches plain English.
Ansible works by connecting to your nodes and pushing out small programs, called Ansible 
modules to them. These programs are written to be resource models of the wanted state of 
the system. Ansible then runs these modules (over SSH by default), and removes them when 
finished. Passwords are supported, but SSH keys with ssh-agent are one of the best ways to 
use Ansible.
OpenShift-Ansible is a set of Ansible playbooks that orchestrate complex deployment tasks, 
including the following examples:
/SM590000Configuring the container runtime environment on virtual machines
/SM590000Provisioning storage for an internal registry
/SM590000Configuring the OpenShift SDN
/SM590000Connecting to authentication systems
Load balancers
This guide uses an external load balancer that is running HAproxy to offer a single entry point 
for the many Red Hat OpenShift Container Platform components. Organizations can provide 
their own deployed load balancers if the service exists.
The Red Hat OpenShift Container Platform console, which is provided by the Red Hat 
OpenShift Container Platform master nodes, can be spread across multiple instances to 
provide load balancing and HA properties.
Application traffic passes through the Red Hat OpenShift Container Platform Router on its 
way to the container processes. The Red Hat OpenShift Container Platform Router is a 
reverse proxy service container that multiplexes the traffic to multiple containers that make up 
a scaled application that is running inside Red Hat OpenShift Container Platform. The load 
balancer that is used by infrastructure nodes acts as the public view for the Red Hat 
OpenShift Container Platform applications.
The destination for the master and application traffic must be set in the load balancer 
configuration after each instance is created, the floating IP address is assigned, and before 
the installation. A single HAproxy Load Balancer can forward both sets of traffic to different 
destinations.
Note: Ansible 2.6 is required for OpenShift 3.11.
Note: Consider the following points:
/SM590000OpenStack Provisioning is not supported by PowerVC. OpenShift-Ansible deploys 
OpenShift on OpenStack by using Heat service, but Heat is not implemented in 
PowerVC.
/SM590000OpenShift-Ansible can also deploy OpenShift directly onto physical servers. This 
reference architecture deploys to virtual machines as that is the more common 
deployment model.