concept pod instance in category kubernetes

This is an excerpt from Manning's book Kubernetes in Action. Login to get full access to this book.

You’ve seen how ReplicationControllers make sure a specific number of pod instances is always running. Because it’s incredibly simple to change the desired number of replicas, this also means scaling pods horizontally is trivial.

Pod replicas managed by a ReplicaSet or ReplicationController are much like cattle. Because they’re mostly stateless, they can be replaced with a completely new pod replica at any time. Stateful pods require a different approach. When a stateful pod instance dies (or the node it’s running on fails), the pod instance needs to be resurrected on another node, but the new instance needs to get the same name, network identity, and state as the one it’s replacing. This is what happens when the pods are managed through a StatefulSet.