Kubespawner deletes PVC even if the pvcNameTemplate doesn't include username

[manics]

Bug description

If a shared dynamically created PVC is used and a JupyterHub user is deleted KubeSpawner will incorrectly delete the shared PVC.

How to reproduce

Use this Z2JH singleuser.storage config with the latest release 4.1.0

singleuser:
  storage:
    dynamic:
      storageClass: nfs
      pvcNameTemplate: claim-jupyter
      subPath: "{user_server}"

This is not a typical configuration since Z2JH's PVC support is used purely for convenience to create just a single shared PVC. However it's possible to conceive of other semi-static pvcNameTemplate, for example you could use profileList with kubespawner_overrides to set pvcNameTemplate=<profilename> to have a shared volume across multiple users.

Expected behaviour

PVC should not be deleted

Actual behaviour

It's deleted- though in practice it may get stuck because of the subPaths

Your personal set up

• OS:

• Version(s):

Full environment

# paste output of `pip freeze` or `conda list` here

Configuration

# jupyterhub_config.py

Logs

[manics]

As it happens overriding the PVC template in `kubespawner_overrides won't work at the moment:

• https://github.com/jupyterhub/kubespawner/issues/761
• https://github.com/jupyterhub/kubespawner/pull/820

so the only way to run into this bug is if KubeSpawner.pvc_name_template is set

https://github.com/jupyterhub/kubespawner/pull/744 stores the PVC name in the spawner state, so to know whether it's safe to delete a PVC we'd need to assert that the current PVC name matches the current pvc_name_template, and that pvc_name_template contains a username variable.