The purpose for the Kubernetes replica set and the
OpenShift Container Platform replication controller
is to ensure the specified number of pod replicas are
running at all times:
If pods exit, or are deleted, the replica set or
replication controller will start more pods. However,
if more pods are running than needed, the replica set
deletes as many as necessary to match the specified
number of replicas.
My question is, does not the replication controller get
in on the action when there is an excess of pods running?
To my knowledge you use either the replication controller or a replicaset and never both at the same time. It think the replicaset is a little more flexible although I cant say that I think the official OpenShift documentation is clear on this.
"Similar to a replication controller, a replica set ensures that a specified number of pod replicas are running at any given time. The difference between a replica set and a replication controller is that a replica set supports set-based selector requirements whereas a replication controller only supports equality-based selector requirements."