We now need to update our stateful-set.yaml file to use the do-block-storage StorageClass. Under the StatefulSet spec (.spec), add a new field called volumeClaimTemplates with the following value:

apiVersion: apps/v1
kind: StatefulSet
metadata: ...
spec:
  volumeClaimTemplates:
  - metadata:
      name: data
    spec:
      accessModes:
      - ReadWriteOnce
      resources:
        requests:
          storage: 2Gi
      storageClassName: do-block-storage

This will use the do-block-storage class to dynamically provision 2 GB PersistentVolumeClaim Objects for any containers which mount it. The PVC is given the name data as a reference.

To mount it to a container, add a volumeMounts property under the spec property of the container spec:

apiVersion: apps/v1
kind: StatefulSet
metadata: ...
spec:
  ...
  template:
    ...
    spec:
      initContainers: ...
      containers: ...
      volumeMounts:
        - name: data
          mountPath: /usr/share/elasticsearch/data
  volumeClaimTemplates: ...

Elasticsearch writes its data to /usr/share/elasticsearch/data, so that's the data we want to persist.