New in 2.8 beta1…
Juju k8s charms are able to specify a deployment type:
- stateless (maps to DeploymentController)
- stateful (maps to StatefulSet)
- daemon (maps to DaemonSet)
Until now, if a charm wanted to declare storage, Juju required that a StatefulSet be used.
It’s now possible for a charm to use Juju storage and have its workload provisioned as a DeploymentController or DaemonSet. Such deployments need to have the shared) volume mounted with access mode as ReadWriteMany or ReadOnlyMany. The way to specify this in Juju is to create a storage pool with the new storage-mode attribute set. The storage pool will specify the k8s StorageClass to use, and the access mode. This storage pool is then used at deploy time with the relevant --storage directive.
A storage pool used for k8s can refer to an existing storage class or specify a provisioner to use and Juju will create a new storage class with that provisioner.
For this example we’ll refer to an existing storage class.
$ kubectl get sc
NAME PROVISIONER RECLAIMPOLICY VOLUMEBINDINGMODE ALLOWVOLUMEEXPANSION AGE
mysc (default) microk8s.io/hostpath Delete Immediate false 7d
Create a storage pool
$ juju create-storage-pool myrwx-storage storage-class=mysc storage-mode=RWX
Deploy a charm with storage
$ juju deploy mycharm --storage database=myrwx-storage,1G
Check that the volume claim is correctly set up
$ kubectl -n test get pvc
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE
database-ab043c08-mycharm-0 Bound pvc-f2ea9bc5-0a61-43ac-b7d2-65dae5d4400d 1Gi RWX mysc 88m