Restoring to Replicated Storage

Steps to Restore from cStor Backup to Replicated Storage for Distributed DBs (Cassandra)

Cassandra is a popular NoSQL database used for handling large amounts of data with high availability and scalability. In Kubernetes environments, managing and restoring Cassandra backups efficiently is crucial. In this article, we will walk you through the process of restoring a Cassandra database in a Kubernetes cluster using Velero, and we will change the storage class to Replicated Storage (a.k.a Replicated Engine or Mayastor) for improved performance.

info

Before you begin, make sure you have the following:

• Access to a Kubernetes cluster with Velero installed.
• A backup of your Cassandra database created using Velero.
• Replicated Storage configured in your Kubernetes environment.

Step 1: Set Up Kubernetes Credentials and Install Velero

Set up your Kubernetes cluster credentials for the target cluster where you want to restore your Cassandra database. Use the same values for the BUCKET-NAME and SECRET-FILENAME placeholders that you used during the initial Velero installation. This ensures that Velero has the correct credentials to access the previously saved backups. Use the gcloud command if you are using Google Kubernetes Engine (GKE) as shown below:

gcloud container clusters get-credentials CLUSTER_NAME --zone ZONE --project PROJECT_NAME

Install Velero with the necessary plugins, specifying your backup bucket, secret file, and uploader type. Make sure to replace the placeholders with your specific values:

velero get backup | grep YOUR_BACKUP_NAME

Step 2: Verify Backup Availability and Check BackupStorageLocation Status

Confirm that your Cassandra backup is available in Velero. This step ensures that there are no credentials or bucket mismatches:

velero get backup | grep YOUR_BACKUP_NAME

Check the status of the BackupStorageLocation to ensure it is available:

kubectl get backupstoragelocation -n velero

Step 3: Create a Restore Request

Create a Velero restore request for your Cassandra backup:

velero restore create RESTORE_NAME --from-backup YOUR_BACKUP_NAME

Step 4: Monitor Restore Progress

Monitor the progress of the restore operation using the below commands:

Velero initiates the restore process by creating an initialization container within the application pod. This container is responsible for restoring the volumes from the backup. As the restore operation proceeds, you can track its status, which typically transitions from in progress to Completed.

In this scenario, the storage class for the PVCs remains as cstor-csi-disk since these PVCs were originally imported from a cStor volume.

note

Your storage class was originally set to cstor-csi-disk because you imported this PVC from a cStor volume, the status might temporarily stay as In Progress and your PVC will be in Pending status.

velero get restore | grep RESTORE_NAME

Inspect the status of the PVCs in the cassandra namespace:

kubectl get pvc -n cassandra

kubectl get pods -n cassandra

Step 5: Back Up PVC YAML

Create a backup of the Persistent Volume Claims (PVCs) and then modify their storage class to mayastor-single-replica.

note

The statefulset for Cassandra will still have the cstor-csi-disk storage class at this point. This will be addressed in the further steps.

kubectl get pvc -n cassandra -o yaml > cassandra_pvc_19-09.yaml

ls -lrt | grep cassandra_pvc_19-09.yaml

Edit the PVC YAML to change the storage class to mayastor-single-replica. You can use the provided example YAML snippet and apply it to your PVCs.

apiVersion: v1

items:

- apiVersion: v1

kind: PersistentVolumeClaim

metadata:

finalizers:

- kubernetes.io/pvc-protection

labels:

app.kubernetes.io/instance: cassandra

app.kubernetes.io/name: cassandra

velero.io/backup-name: cassandra-backup-19-09-23

velero.io/restore-name: cassandra-restore-19-09-23

name: data-cassandra-0

namespace: cassandra

spec:

accessModes:

- ReadWriteOnce

resources:

requests:

storage: 3Gi

storageClassName: mayastor-single-replica

volumeMode: Filesystem

- apiVersion: v1

kind: PersistentVolumeClaim

metadata:

finalizers:

- kubernetes.io/pvc-protection

labels:

app.kubernetes.io/instance: cassandra

app.kubernetes.io/name: cassandra

velero.io/backup-name: cassandra-backup-19-09-23

velero.io/restore-name: cassandra-restore-19-09-23

name: data-cassandra-1

namespace: cassandra

spec:

accessModes:

- ReadWriteOnce

resources:

requests:

storage: 3Gi

storageClassName: mayastor-single-replica

volumeMode: Filesystem

- apiVersion: v1

kind: PersistentVolumeClaim

metadata:

finalizers:

- kubernetes.io/pvc-protection

labels:

app.kubernetes.io/instance: cassandra

app.kubernetes.io/name: cassandra

velero.io/backup-name: cassandra-backup-19-09-23

velero.io/restore-name: cassandra-restore-19-09-23

name: data-cassandra-2

namespace: cassandra

spec:

accessModes:

- ReadWriteOnce

resources:

requests:

storage: 3Gi

storageClassName: mayastor-single-replica

volumeMode: Filesystem

kind: List

metadata:

resourceVersion: ""

Step 6: Delete and Recreate PVCs

Delete the pending PVCs and apply the modified PVC YAML to recreate them with the new storage class:

kubectl delete pvc PVC_NAMES -n cassandra

kubectl apply -f cassandra_pvc.yaml -n cassandra

Step 7: Observe Velero Init Container and Confirm Restore

Observe the Velero init container as it restores the volumes for the Cassandra pods. This process ensures that your data is correctly recovered.

Events:

Type Reason Age From Message

---- ------ ---- ---- -------

Warning FailedScheduling 8m37s default-scheduler 0/3 nodes are available: 3 pod has unbound immediate PersistentVolumeClaims. preemption: 0/3 nodes are available: 3 Preemption is not helpful for scheduling.

Warning FailedScheduling 8m36s default-scheduler 0/3 nodes are available: 3 pod has unbound immediate PersistentVolumeClaims. preemption: 0/3 nodes are available: 3 Preemption is not helpful for scheduling.

Warning FailedScheduling 83s default-scheduler 0/3 nodes are available: 3 persistentvolumeclaim "data-cassandra-0" not found. preemption: 0/3 nodes are available: 3 Preemption is not helpful for scheduling.

Warning FailedScheduling 65s default-scheduler running PreFilter plugin "VolumeBinding": %!!(MISSING)w(<nil>)

Normal Scheduled 55s default-scheduler Successfully assigned cassandra/cassandra-0 to gke-mayastor-pool-2acd09ca-4v3z

Normal NotTriggerScaleUp 3m34s (x31 over 8m35s) cluster-autoscaler pod didn't trigger scale-up:

Normal SuccessfulAttachVolume 55s attachdetach-controller AttachVolume.Attach succeeded for volume "pvc-bf8a2fb7-8ddb-4e53-aa48-f8bbf2064b41"

Normal Pulled 47s kubelet Container image "velero/velero-restore-helper:v1.11.1" already present on machine

Normal Created 47s kubelet Created container restore-wait

Normal Started 47s kubelet Started container restore-wait

Normal Pulled 41s kubelet Container image "docker.io/bitnami/cassandra:4.1.3-debian-11-r37" already present on machine

Normal Created 41s kubelet Created container cassandra

Normal Started 41s kubelet Started container cassandra

Run this command to check the restore status:

velero get restore | grep cassandra-restore-19-09-23

Run this command to check if all the pods are running:

kubectl get pods -n cassandra

Step 8: Verify Cassandra Data and StatefulSet

Access a Cassandra Pod using cqlsh and Check the Data

• You can use the following command to access the Cassandra pods. This command establishes a connection to the Cassandra database running on pod cassandra-1:

cqlsh -u <enter-your-user-name> -p <enter-your-password> cassandra-1.cassandra-headless.cassandra.svc.cluster.local 9042

• The query results should display the data you backed up from cStor. In your output, youare expecting to see the data you backed up.

cassandra@cqlsh> USE openebs;

cassandra@cqlsh:openebs> select * from openebs.data;

replication | appname | volume

-------------+-----------+--------

3 | cassandra | cStor

(1 rows)

• After verifying the data, you can exit the Cassandra shell by typing exit.

Modify your Cassandra StatefulSet YAML to use the Replicated Storage-Single-Replica Storage Class

• Before making changes to the Cassandra StatefulSet YAML, create a backup to preserve the existing configuration by running the following command:

kubectl get sts cassandra -n cassandra -o yaml > cassandra_sts_backup.yaml

• You can modify the Cassandra StatefulSet YAML to change the storage class to mayastor-single-replica. Here is the updated YAML:

apiVersion: apps/v1

kind: StatefulSet

metadata:

annotations:

meta.helm.sh/release-name: cassandra

meta.helm.sh/release-namespace: cassandra

labels:

app.kubernetes.io/instance: cassandra

app.kubernetes.io/managed-by: Helm

app.kubernetes.io/name: cassandra

helm.sh/chart: cassandra-10.5.3

velero.io/backup-name: cassandra-backup-19-09-23

velero.io/restore-name: cassandra-restore-19-09-23

name: cassandra

namespace: cassandra

spec:

podManagementPolicy: OrderedReady

replicas: 3

revisionHistoryLimit: 10

selector:

matchLabels:

app.kubernetes.io/instance: cassandra

app.kubernetes.io/name: cassandra

serviceName: cassandra-headless

template:

# ... (rest of the configuration remains unchanged)

updateStrategy:

type: RollingUpdate

volumeClaimTemplates:

- apiVersion: v1

kind: PersistentVolumeClaim

metadata:

creationTimestamp: null

labels:

app.kubernetes.io/instance: cassandra

app.kubernetes.io/name: cassandra

name: data

spec:

accessModes:

- ReadWriteOnce

resources:

requests:

storage: 3Gi

storageClassName: mayastor-single-replica # Change the storage class here

volumeMode: Filesystem

• Apply the modified YAML to make the changes take effect:

kubectl apply -f cassandra_sts_modified.yaml

Delete the Cassandra StatefulSet with the --cascade=orphan Flag

Delete the Cassandra StatefulSet while keeping the pods running without controller management:

kubectl delete sts cassandra -n cassandra --cascade=orphan

Recreate the Cassandra StatefulSet using the Updated YAML

• Use the kubectl apply command to apply the modified StatefulSet YAML configuration file, ensuring you are in the correct namespace where your Cassandra deployment resides. Replace <path_to_your_yaml> with the actual path to your YAML file.

kubectl apply -f <path_to_your_yaml> -n cassandra

• To check the status of the newly created StatefulSet, run:

kubectl get sts -n cassandra

• To confirm that the pods are running and managed by the controller, run:

kubectl get pods -n cassandra

See Also

• Migration from Legacy Storage to Latest Storage Solution
• Migration for Replicated DB