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5.2. Dynamic Provisioning of Volumes

Dynamic provisioning enables provisioning of Red hat Gluster Storage volume to a running application container without having to pre-create the volume. The volume will be created dynamically as the claim request comes in, and a volume of exactly the same size will be provisioned to the application containers.

Note

Dynamically provisioned Volumes are supported from Container Native Storage 3.4. If you have any statically provisioned volumes and require more information about managing it, then refer Section 5.1, “Static Provisioning of Volumes”

5.2.1. Configuring Dynamic Provisioning of Volumes

To configure dynamic provisioning of volumes, the administrator must define StorageClass objects that describe named "classes" of storage offered in a cluster. After creating a Storage Class, a secret for heketi authentication must be created before proceeding with the creation of persistent volume claim.

5.2.1.1. Registering a Storage Class

When configuring a StorageClass object for persistent volume provisioning, the administrator must describe the type of provisioner to use and the parameters that will be used by the provisioner when it provisions a PersistentVolume belonging to the class.
  1. To create a storage class execute the following command: 
    # cat glusterfs-storageclass.yaml


apiVersion: storage.k8s.io/v1beta1
kind: StorageClass
metadata:
  name: gluster-container
provisioner: kubernetes.io/glusterfs
parameters:
  resturl: "http://heketi-storage-project.cloudapps.mystorage.com"
  restuser: "admin"
  volumetype: "replicate:3"
  clusterid: "630372ccdc720a92c681fb928f27b53f,796e6db1981f369ea0340913eeea4c9a"
  secretNamespace: "default"
  secretName: "heketi-secret"
    where,
    resturl: Gluster REST service/Heketi service url which provision gluster volumes on demand. The general format must be IPaddress:Port and this is a mandatory parameter for GlusterFS dynamic provisioner. If Heketi service is exposed as a routable service in openshift/kubernetes setup, this can have a format similar to http://heketi-storage-project.cloudapps.mystorage.com where the fqdn is a resolvable heketi service url.
    restuser : Gluster REST service/Heketi user who has access to create volumes in the trusted storage pool
    volumetype: It specifies the volume type that is being used.

    Note

    Distributed-Three-way replication is the only supported volume type.
    clusterid: It is the ID of the cluster which will be used by Heketi when provisioning the volume. It can also be a list of comma separated cluster IDs. This is an optional parameter.

    Note

    To get the cluster ID, execute the following command: 
    # heketi-cli cluster list
    secretNamespace + secretName: Identification of Secret instance that contains the user password that is used when communicating with the Gluster REST service. These parameters are optional. Empty password will be used when both secretNamespace and secretName are omitted.

    Note

    When the persistent volumes are dynamically provisioned, the Gluster plugin automatically creates an endpoint and a headless service in the name gluster-dynamic-<claimname>. This dynamic endpoint and service will be deleted automatically when the persistent volume claim is deleted.
  2. To register the storage class to Openshift, execute the following command: 
    # oc create -f glusterfs-storageclass.yaml
storageclass "gluster-container" created
  3. To get the details of the storage class, execute the following command: 
    # oc describe storageclass gluster-container
                               
Name: gluster-container
IsDefaultClass: No
Annotations: <none>
Provisioner: kubernetes.io/glusterfs
Parameters: resturl=http://heketi-storage-project.cloudapps.mystorage.com,restuser=admin,secretName=heketi-secret,secretNamespace=default
No events.

5.2.1.2. Creating Secret for Heketi Authentication

To create a secret for Heketi authentication, execute the following commands:
  1. Create an encoded value for the password by executing the following command: 
    # echo -n "mypassword" | base64
    where “mypassword” is Heketi’s admin user password.
    For example: 
    # echo -n "mypassword" | base64
bXlwYXNzd29yZA==
  2. Create a secret file. A sample secret file is provided below: 
    # cat glusterfs-secret.yaml
                               
apiVersion: v1
kind: Secret
metadata:
  name: heketi-secret
  namespace: default
data:
  # base64 encoded password. E.g.: echo -n "mypassword" | base64
  key: bXlwYXNzd29yZA==
type: kubernetes.io/glusterfs
  3. Register the secret on Openshift by executing the following command: 
    # oc create -f glusterfs-secret.yaml
secret "heketi-secret" created

5.2.1.3. Creating a Persistent Volume Claim

To create a persistent volume claim execute the following commands:
  1. Create a Persistent Volume Claim file. A sample persistent volume claim is provided below: 
    # cat glusterfs-pvc-claim1.yaml
                               
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: claim1
  annotations:
    volume.beta.kubernetes.io/storage-class: gluster-container
spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 4Gi
  2. Register the claim by executing the following command: 
    # oc create -f glusterfs-pvc-claim1.yaml
persistentvolumeclaim "claim1" created
  3. To get the details of the claim, execute the following command: 
    # oc describe pvc <claim_name>
    For example: 
    # oc describe pvc claim1
                               
Name: claim1
Namespace: default
StorageClass: gluster-container
Status: Bound
Volume: pvc-54b88668-9da6-11e6-965e-54ee7551fd0c
Labels: <none>
Capacity: 4Gi
Access Modes: RWO
No events.

5.2.1.4. Verifying Claim Creation

To verify if the claim is created, execute the following commands:
  1. To get the details of the persistent volume claim and persistent volume, execute the following command: 
    # oc get pv,pvc

NAME                                          CAPACITY   ACCESSMODES   RECLAIMPOLICY   STATUS     CLAIM                    REASON    AGE
pv/pvc-962aa6d1-bddb-11e6-be23-5254009fc65b   4Gi        RWO           Delete          Bound      storage-project/claim1             3m

NAME         STATUS    VOLUME                                     CAPACITY   ACCESSMODES   AGE
pvc/claim1   Bound     pvc-962aa6d1-bddb-11e6-be23-5254009fc65b   4Gi        RWO           4m
  2. To validate if the endpoint and the services are created as part of claim creation, execute the following command: 
    # oc get endpoints,service

NAME                          ENDPOINTS                                            AGE
ep/storage-project-router     192.168.68.3:443,192.168.68.3:1936,192.168.68.3:80   28d
ep/gluster-dynamic-claim1     192.168.68.2:1,192.168.68.3:1,192.168.68.4:1         5m
ep/heketi                     10.130.0.21:8080                                     21d
ep/heketi-storage-endpoints   192.168.68.2:1,192.168.68.3:1,192.168.68.4:1         25d

NAME                           CLUSTER-IP       EXTERNAL-IP   PORT(S)                   AGE
svc/storage-project-router     172.30.166.64    <none>        80/TCP,443/TCP,1936/TCP   28d
svc/gluster-dynamic-claim1     172.30.52.17     <none>        1/TCP                     5m
svc/heketi                     172.30.129.113   <none>        8080/TCP                  21d
svc/heketi-storage-endpoints   172.30.133.212   <none>        1/TCP                     25d

5.2.1.5. Using the Claim in a Pod

Execute the following steps to use the claim in a pod.
  1. To use the claim in the application, for example 
    # cat app.yaml

apiVersion: v1
kind: Pod
metadata:
  name: busybox
spec:
  containers:
    - image: busybox
      command:
        - sleep
        - "3600"
      name: busybox
      volumeMounts:
        - mountPath: /usr/share/busybox
          name: mypvc
  volumes:
    - name: mypvc
      persistentVolumeClaim:
        claimName: claim1
    # oc create -f app.yaml
pod "busybox" created
    For more information about using the glusterfs claim in the application see, https://access.redhat.com/documentation/en/openshift-container-platform/3.5/single/installation-and-configuration/#install-config-storage-examples-gluster-example.
  2. To verify that the pod is created, execute the following command: 
    # oc get pods

NAME                                READY     STATUS         RESTARTS   AGE
storage-project-router-1-at7tf      1/1       Running        0          13d
busybox                             1/1       Running        0          8s
glusterfs-dc-192.168.68.2-1-hu28h   1/1       Running        0          7d
glusterfs-dc-192.168.68.3-1-ytnlg   1/1       Running        0          7d
glusterfs-dc-192.168.68.4-1-juqcq   1/1       Running        0          13d
heketi-1-9r47c                      1/1       Running        0          13d
  3. To verify that the persistent volume is mounted inside the container, execute the following command: 
    # oc rsh busybox
    / $ df -h
Filesystem                Size      Used Available Use% Mounted on
/dev/mapper/docker-253:0-666733-38050a1d2cdb41dc00d60f25a7a295f6e89d4c529302fb2b93d8faa5a3205fb9
                         10.0G     33.8M      9.9G   0% /
tmpfs                    23.5G         0     23.5G   0% /dev
tmpfs                    23.5G         0     23.5G   0% /sys/fs/cgroup
/dev/mapper/rhgs-root
                         17.5G      3.6G     13.8G  21% /run/secrets
/dev/mapper/rhgs-root
                         17.5G      3.6G     13.8G  21% /dev/termination-log
/dev/mapper/rhgs-root
                         17.5G      3.6G     13.8G  21% /etc/resolv.conf
/dev/mapper/rhgs-root
                         17.5G      3.6G     13.8G  21% /etc/hostname
/dev/mapper/rhgs-root
                         17.5G      3.6G     13.8G  21% /etc/hosts
shm                      64.0M         0     64.0M   0% /dev/shm
192.168.68.2:vol_5b05cf2e5404afe614f8afa698792bae
                          4.0G     32.6M      4.0G   1% /usr/share/busybox
tmpfs                    23.5G     16.0K     23.5G   0% /var/run/secrets/kubernetes.io/serviceaccount
tmpfs                    23.5G         0     23.5G   0% /proc/kcore
tmpfs                    23.5G         0     23.5G   0% /proc/timer_stats

5.2.1.6. Deleting a Persistent Volume Claim

  1. To delete a claim, execute the following command: 
    # oc delete pvc <claim-name>
    For example: 
    # oc delete pvc claim1
persistentvolumeclaim "claim1" deleted
  2. To verify if the claim is deleted, execute the following command: 
    # oc get pvc <claim-name>
    For example: 
    # oc get pvc claim1
No resources found.
    When the user deletes a persistent volume claim that is bound to a persistent volume created by dynamic provisioning, apart from deleting the persistent volume claim, Kubernetes will also delete the persistent volume, endpoints, service, and the actual volume. Execute the following commands if this has to be verified:
    • To verify if the persistent volume is deleted, execute the following command: 
      # oc get pv <pv-name>
      For example: 
      # oc get pv pvc-962aa6d1-bddb-11e6-be23-5254009fc65b 
No resources found.
    • To verify if the endpoints are deleted, execute the following command: 
      # oc get endpoints <endpointname>
      For example: 
      # oc get endpoints gluster-dynamic-claim1
No resources found.
    • To verify if the service is deleted, execute the following command: 
      # oc get service <servicename>
      For example: 
      # oc get service gluster-dynamic-claim1 
No resources found.