How to let Kubernetes PetSet use existing Persistent Volumes?

Question

As part of the PetSet definition, the volumeClainTemplates are defined for Kubernetes to dynamically generate Persistent Volume Claims. For example:

  volumeClaimTemplates:
  - metadata:
      name: datadir
      annotations:
        volume.alpha.kubernetes.io/storage-class: anything
    spec:
      accessModes: [ "ReadWriteOnce" ]
      resources:
        requests:
          storage: 24Gi

However, I already has a few of the Persistent Volumes defined:

#kubectl get pv    
NAME      CAPACITY   ACCESSMODES   RECLAIMPOLICY   STATUS    CLAIM                 REASON    AGE 
pv-1-rw   24Gi       RWO           Retain          Bound     rnd/pvc-1-rw             1h
pv-2-rw   24Gi       RWO           Retain          Bound     rnd/pvc-2-rw             6d
pv-3-rw   24Gi       RWO           Retain          Bound     rnd/pvc-3-rw             6d
...

I would like the Kubernetes to choose the persistent volumes from the existing ones rather than dynamically creating new ones.

I'm using Kubernetes 1.4.3. Does anyone know how to do that?

Answer 1

volumeClaimTemplates is an array of PersistentVolumeClaim. You can try to define them using selector and label existing volumes somehow, i.e.:

kind: PersistentVolume
apiVersion: v1
metadata:
  name: pv0001
  labels:
    foo: foo
    bar: bar
spec:
  accessModes:
    - ReadWriteOnce
  capacity:
    storage: 5Gi
  hostPath:
    path: /data/pv0001/
---
kind: PersistentVolume
apiVersion: v1
metadata:
  name: pv0002
  labels:
    foo: foo
    bar: bar
spec:
  accessModes:
    - ReadWriteOnce
  capacity:
    storage: 5Gi
  hostPath:
    path: /data/pv0002/
---
kind: Service
apiVersion: v1
metadata:
  name: nginx
  labels:
    app: nginx
spec:
  ports:
    - port: 80
  selector:
    app: nginx
---
kind: PetSet
apiVersion: apps/v1alpha1
metadata:
  name: nginx
spec:
  serviceName: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
        - name: nginx
          image: gcr.io/google_containers/nginx-slim:0.8
          ports:
            - containerPort: 80
          volumeMounts:
            - name: html
              mountPath: /usr/share/nginx/html
  volumeClaimTemplates:
    - metadata:
        name: html
      spec:
        accessModes:
          - ReadWriteOnce
        resources:
          requests:
            storage: 5Gi
        selector:
          matchLabels:
            foo: foo
            bar: bar

Of course, volumes must be available for bounding.

$ kubectl get pvc html-nginx-0
NAME           STATUS    VOLUME    CAPACITY   ACCESSMODES   AGE
html-nginx-0   Bound     pv0002    5Gi        RWO           1m
$ kubectl get pv
NAME      CAPACITY   ACCESSMODES   RECLAIMPOLICY   STATUS      CLAIM                  REASON    AGE
pv0001    5Gi        RWO           Retain          Available                                    2m
pv0002    5Gi        RWO           Retain          Bound       default/html-nginx-0             2m