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Lab 3.3: Persistent Storage

In this lab we take a look at the OpenShift implementation of Container Native Storage using the heketi-cli to resize a volume.

heketi-cli

The package heketi-client has been pre-installed for you on the bastion host. The package includes the heketi-cli command. In order to use heketi-cli, we need the server's URL and admin key:

[ec2-user@master0 ~]$ oc describe pod -n glusterfs | grep HEKETI_ADMIN_KEY
      HEKETI_ADMIN_KEY:			[HEKETI_ADMIN_KEY]

We can then set variables with this information:

[ec2-user@master0 ~]$ export HEKETI_CLI_USER=admin
[ec2-user@master0 ~]$ export HEKETI_CLI_KEY="[HEKETI_ADMIN_KEY]"
[ec2-user@master0 ~]$ export HEKETI_CLI_SERVER=$(oc get svc/heketi-storage -n glusterfs --template "http://{{.spec.clusterIP}}:{{(index .spec.ports 0).port}}")

Verify that everything is set as it should:

[ec2-user@master0 ~]$ env | grep -i heketi
HEKETI_CLI_KEY=[PASSWORD]
HEKETI_CLI_SERVER=http://172.30.250.14:8080
HEKETI_CLI_USER=admin

Now we can run some useful commands for troubleshooting.

Get all volumes and then show details of a specific volume using its id:

[ec2-user@master0 ~]$ heketi-cli volume list
Id:255b9535ee460dfa696a7616b57a7035    Cluster:bc64bf1b4a4e7cc0702d28c7c02674cf    Name:glusterfs-registry-volume
Id:e5baabb2bca5ba5cdd749d48d47c4e89    Cluster:bc64bf1b4a4e7cc0702d28c7c02674cf    Name:heketidbstorage

[ec2-user@master0 ~]$ heketi-cli volume info 255b9535ee460dfa696a7616b57a7035
...

Get the cluster id and details of the cluster:

[ec2-user@master0 ~]$ heketi-cli cluster list
Clusters:
Id:bc64bf1b4a4e7cc0702d28c7c02674cf [file][block]
[ec2-user@master0 ~]$ heketi-cli cluster info bc64bf1b4a4e7cc0702d28c7c02674cf
...

Get nodes and details of a specific node using its id:

[ec2-user@master0 ~]$ heketi-cli node list
Id:3efc4d8267eb3b65c2d3ed9848aa4328	Cluster:bc64bf1b4a4e7cc0702d28c7c02674cf
Id:c0de1021e7577c26721b22003c14427c	Cluster:bc64bf1b4a4e7cc0702d28c7c02674cf
Id:c9612d0eee19146642f51dc2f3d484e5	Cluster:bc64bf1b4a4e7cc0702d28c7c02674cf
[ec2-user@master0 ~]$ heketi-cli node info c9612d0eee19146642f51dc2f3d484e5
...

Show the whole topology:

[ec2-user@master0 ~]$ heketi-cli topology info
...

Set Default Storage Class

A StorageClass provides a way to describe a certain type of storage. Different classes might map to different storage types (e.g. nfs, gluster, ...), quality-of-service levels, to backup policies or to arbitrary policies determined by the cluster administrators. In our case we only have one storage class which is glusterfs-storage:

[ec2-user@master0 ~]$ oc get storageclass

By setting the anotation storageclass.kubernetes.io/is-default-class on a StorageClass we make it the default storage class on an OpenShift cluster:

[ec2-user@master0 ~]$ oc patch storageclass glusterfs-storage -p  '{"metadata": {"annotations":{"storageclass.kubernetes.io/is-default-class":"true"}}}'

If then someone creates a pvc and does not specify the StorageClass, the DefaultStorageClass admission controller does automatically set the StorageClass to the DefaultStorageClass.

Note: We could have set the Ansible inventory variable openshift_storage_glusterfs_storageclass_default to true during installation in order to let the playbooks automatically do what we just did by hand. For demonstration purposes however we set it to false.

Create and Delete a Persistent Volume Claim

If you create a PersistentVolumeClaim, Heketi will automatically create a PersistentVolume and bind it to your claim. Likewise if you delete a claim, Heketi will delete the PersistentVolume.

Create a new project and create a pvc:

[ec2-user@master0 ~]$ oc new-project labelle
Now using project "labelle" on server "https://console.user[X].lab.openshift.ch:8443".
...
[ec2-user@master0 ~]$ cat <<EOF >pvc.yaml
apiVersion: "v1"
kind: "PersistentVolumeClaim"
metadata:
  name: "testclaim"
spec:
  accessModes:
    - "ReadWriteOnce"
  resources:
    requests:
      storage: "1Gi"
EOF

[ec2-user@master0 ~]$ oc create -f pvc.yaml
persistentvolumeclaim "testclaim" created

Check if the pvc could be bound to a new volume:

[ec2-user@master0 ~]$ oc get pvc
NAME        STATUS    VOLUME                                     CAPACITY   ACCESSMODES   STORAGECLASS        AGE
testclaim   Bound     pvc-839223fd-30d4-11e8-89f3-067e4f48dfe4   1Gi        RWO           glusterfs-storage   38s

[ec2-user@master0 ~]$ oc get pv
NAME                                       CAPACITY   ACCESSMODES   RECLAIMPOLICY   STATUS    CLAIM                    STORAGECLASS        REASON    AGE
pvc-839223fd-30d4-11e8-89f3-067e4f48dfe4   1Gi        RWO           Delete          Bound     labelle/testclaim        glusterfs-storage             41s
...

Delete the claim and check if the volume gets deleted:

[ec2-user@master0 ~]$ oc delete pvc testclaim
persistentvolumeclaim "testclaim" deleted
[ec2-user@master0 ~]$ oc get pv

[ec2-user@master0 ~]$ oc delete project labelle

Resize Existing Volume

We will resize the registry volume with heketi-cli.

First we need to know which volume is in use for the registry:

[ec2-user@master0 ~]$ oc get pvc registry-claim -n default
NAME             STATUS    VOLUME            CAPACITY   ACCESSMODES   STORAGECLASS   AGE
registry-claim   Bound     registry-volume   5Gi        RWX                          2d

[ec2-user@master0 ~]$ oc describe pv registry-volume | grep Path
    Path:		glusterfs-registry-volume

[ec2-user@master0 ~]$ heketi-cli volume list | grep glusterfs-registry-volume
Id:255b9535ee460dfa696a7616b57a7035    Cluster:bc64bf1b4a4e7cc0702d28c7c02674cf    Name:glusterfs-registry-volume

Now we can extend the volume from 5Gi to 6Gi:

[ec2-user@master0 ~]$ heketi-cli volume expand --volume=255b9535ee460dfa696a7616b57a7035 --expand-size=1
Name: glusterfs-registry-volume
Size: 6
...

Check if the gluster volume has the new size:

[ec2-user@master0 ~]$ ansible infra_nodes -m shell -a "df -ah" | grep glusterfs-registry-volume
172.31.40.96:glusterfs-registry-volume  6.0G  317M  5.7G   3% /var/lib/origin/openshift.local.volumes/pods/d8dc2712-3bcf-11e8-90a6-066961eacc9a/volumes/kubernetes.io~glusterfs/registry-volume

In order for the persistent volume's information and the actually available space to be consistent, we're going to edit the pv's specification:

[ec2-user@master0 ~]$ oc get pv
NAME              CAPACITY   ACCESSMODES   RECLAIMPOLICY   STATUS    CLAIM                    STORAGECLASS   REASON    AGE
registry-volume   5Gi        RWX           Retain          Bound     default/registry-claim                            1d
[ec2-user@master0 ~]$ oc patch pv registry-volume -p '{"spec":{"capacity":{"storage":"6Gi"}}}'
[ec2-user@master0 ~]$ oc get pv
NAME              CAPACITY   ACCESSMODES   RECLAIMPOLICY   STATUS    CLAIM                    STORAGECLASS   REASON    AGE
registry-volume   6Gi        RWX           Retain          Bound     default/registry-claim                            1d

End of Lab 3.3

3.4 Renew Certificates →

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