In this exercise, we will learn how to deploy a stateful workload on OpenEBS persistent volume.
Storage Classes are the foundation of dynamic provisioning in Kubernetes, allowing cluster administrators to define abstractions for the underlying storage platform. Users simply refer to a StorageClass by name in the PersistentVolumeClaim (PVC) using the “storageClassName” parameter.
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Let's take a look at one.
$ kubectl describe sc openebs-mongodb Name: openebs-mongodb IsDefaultClass: No Annotations: kubectl.kubernetes.io/last-applied-configuration={"apiVersion":"storage.k8s.io/v1","kind":"StorageClass","metadata":{"annotations":{},"name":"openebs-mongodb","namespace":""},"parameters":{"openebs.io/capacity":"5G","openebs.io/fstype":"xfs","openebs.io/jiva-replica-count":"3","openebs.io/storage-pool":"default","openebs.io/volume-monitor":"true"},"provisioner":"openebs.io/provisioner-iscsi"} Provisioner: openebs.io/provisioner-iscsi Parameters: openebs.io/capacity=5G,openebs.io/fstype=xfs,openebs.io/jiva-replica-count=3,openebs.io/storage-pool=default,openebs.io/volume-monitor=true AllowVolumeExpansion: <unset> MountOptions: <none> ReclaimPolicy: Delete VolumeBindingMode: Immediate Events: <none>
If you set one of the OpenEBS StorageClasses as default StorageClass, then all you need to do is create a PersistentVolumeClaim (PVC) and OpenEBS will take care of the rest – there is no need to specify the storageClassName. You can use Kubernetes annotations to attach arbitrary non-identifying metadata to objects. Clients such as tools and libraries can retrieve this metadata. The OpenEBS operator makes use of these annotations to determine, in this case, what storage class is the default.
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Here is how you can set a default Storage Class:
kubectl patch storageclass openebs-standard -p '{"metadata": {"annotations":{"storageclass.kubernetes.io/is-default-class":"true"}}}' -
Confirm default Storage Class is set:
$ kubectl get sc NAME PROVISIONER AGE openebs-cassandra openebs.io/provisioner-iscsi 1h openebs-es-data-sc openebs.io/provisioner-iscsi 1h openebs-jupyter openebs.io/provisioner-iscsi 1h openebs-kafka openebs.io/provisioner-iscsi 1h openebs-mongodb openebs.io/provisioner-iscsi 1h openebs-percona openebs.io/provisioner-iscsi 1h openebs-redis openebs.io/provisioner-iscsi 1h openebs-standalone openebs.io/provisioner-iscsi 1h openebs-standard (default) openebs.io/provisioner-iscsi 1h openebs-zk openebs.io/provisioner-iscsi 1h snapshot-promoter volumesnapshot.external-storage.k8s.io/snapshot-promoter 1h
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View an example deployment:
cd ~/openebs/k8s/demo/crunchy-postgres/ nano set.json -
Here is how the file should look like, pay attention to the storageClassName parameter:
$ cat set.json { "apiVersion": "apps/v1beta1", "kind": "StatefulSet", "metadata": { "name": "pgset" }, "spec": { "serviceName": "pgset", "replicas": 2, "template": { "metadata": { "labels": { "app": "pgset" } }, "spec": { "securityContext": { "fsGroup": 26 }, "containers": [ { "name": "pgset", "image": "crunchydata/crunchy-postgres:centos7-10.4-1.8.3", "ports": [ { "containerPort": 5432, "name": "postgres" } ], "env": [{ "name": "PG_PRIMARY_USER", "value": "primaryuser" }, { "name": "PGHOST", "value": "/tmp" }, { "name": "PG_MODE", "value": "set" }, { "name": "PG_PRIMARY_PASSWORD", "value": "password" }, { "name": "PG_USER", "value": "testuser" }, { "name": "PG_PASSWORD", "value": "password" }, { "name": "PG_DATABASE", "value": "userdb" }, { "name": "PG_ROOT_PASSWORD", "value": "password" }, { "name": "PG_PRIMARY_PORT", "value": "5432" }, { "name": "PG_PRIMARY_HOST", "value": "pgset-primary" }], "volumeMounts": [ { "name": "pgdata", "mountPath": "/pgdata", "readOnly": false } ] } ] } }, "volumeClaimTemplates": [ { "metadata": { "name": "pgdata" }, "spec": { "accessModes": [ "ReadWriteOnce" ], "storageClassName": "openebs-standard", "resources": { "requests": { "storage": "400M" } } } } ] } }This example will create service and a statefulset that will deploy a primary and replica Postgres pods, both protected by OpenEBS PVs, created by PVCs that are requested by the
openebs-standardstorage class. -
Deploy our example PostgreSQL workload.
./run/sh -
Validate your stateful workload by checking the services, PODs and PVC/PVs created.
$ kubectl get services NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE kubernetes ClusterIP 10.3.0.1 <none> 443/TCP 2h maya-apiserver-service ClusterIP 10.3.0.131 <none> 5656/TCP 1h pgset ClusterIP None <none> 5432/TCP 1m pgset-primary ClusterIP 10.3.0.194 <none> 5432/TCP 1m pgset-replica ClusterIP 10.3.0.146 <none> 5432/TCP 1m pvc-3f188c65-6f60-11e8-9e48-0698b18c8dc8-ctrl-svc ClusterIP 10.3.0.55 <none> 3260/TCP,9501/TCP 1m pvc-658c765c-6f60-11e8-9e48-0698b18c8dc8-ctrl-svc ClusterIP 10.3.0.30 <none> 3260/TCP,9501/TCP 22s$ kubectl get pods NAME READY STATUS RESTARTS AGE maya-apiserver-6cfd67f8-2nlhd 1/1 Running 0 1h openebs-provisioner-6797d44769-dxk82 1/1 Running 0 1h openebs-snapshot-controller-565d8f576d-pj5f9 2/2 Running 0 1h pgset-0 1/1 Running 0 2m pgset-1 1/1 Running 0 1m pvc-3f188c65-6f60-11e8-9e48-0698b18c8dc8-ctrl-6478f9bc5c-mjjv7 2/2 Running 0 2m pvc-3f188c65-6f60-11e8-9e48-0698b18c8dc8-rep-7895ddc9cd-8dpr8 1/1 Running 0 2m pvc-3f188c65-6f60-11e8-9e48-0698b18c8dc8-rep-7895ddc9cd-dxg29 1/1 Running 0 2m pvc-3f188c65-6f60-11e8-9e48-0698b18c8dc8-rep-7895ddc9cd-m9t9q 1/1 Running 0 2m pvc-658c765c-6f60-11e8-9e48-0698b18c8dc8-ctrl-664dfd879f-frztl 2/2 Running 0 1m pvc-658c765c-6f60-11e8-9e48-0698b18c8dc8-rep-fc44bf78c-7jf8m 1/1 Running 0 1m pvc-658c765c-6f60-11e8-9e48-0698b18c8dc8-rep-fc44bf78c-7q75k 1/1 Running 0 1m pvc-658c765c-6f60-11e8-9e48-0698b18c8dc8-rep-fc44bf78c-vxssz 1/1 Running 0 1mConfirm that both pgset-0 and pgest-1 are running and OpenEBS controller with 3 replicas each are created.
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Get the list of PVCs and PVs created for your application.
$ kubectl get pvc NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE pgdata-pgset-0 Bound pvc-3f188c65-6f60-11e8-9e48-0698b18c8dc8 400M RWO openebs-standard 5m pgdata-pgset-1 Bound pvc-658c765c-6f60-11e8-9e48-0698b18c8dc8 400M RWO openebs-standard 4m$ kubectl get pv NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE pvc-3f188c65-6f60-11e8-9e48-0698b18c8dc8 400M RWO Delete Bound default/pgdata-pgset-0 openebs-standard 6m pvc-658c765c-6f60-11e8-9e48-0698b18c8dc8 400M RWO Delete Bound default/pgdata-pgset-1 openebs-standard 4m
Now you have your stateful workload up and running.