Pulp

Research suggests that the best way to do this is a ConfigMap that the operator references. Other operators do this, such as mongodb and another.

The storage can be expanded by uploading a new version of the ConfigMap. It takes seconds for the change to start being applied by the pulp-operator (ansible operator) pod.

However, the StorageClass / provisioner must support it.

The minikube-hostpath provisioner does not, even if you modify its storage class ("Standard".) (This may be due to the lack of the Online File System Expansion feature "ExpandInUsePersistentVolumes").

However, other provisioners do, such as AWS-EBS, GCE-PD, Azure Disk, Azure File, Glusterfs, Cinder, Portworx, and Ceph RBD.
https://kubernetes.io/blog/2018/07/12/resizing-persistent-volumes-using-kubernetes/

I have discovered that the better way to solve this is to use our operator's custom resource.

This is what we already do for the pulp image tag. And it is what the ansible operator framework is designed around.

I plan to rework the existing configmap into the custom resource.