Backup

7. Backup

K8ssandra includes Medusa for Apache Cassandra™ to handle backup and restore for your Cassandra nodes. Recently Medusa was upgraded to introduce support for all S3 compatible backends, including MinIO, the popular k8s-native object storage suite. Let’s see how to set up K8ssandra and MinIO to backup Cassandra in just a few steps.

Deploy MinIO

Similar to K8ssandra, MinIO can be simply deployed through Helm.

helm repo add minio https://helm.min.io/

The MinIO Helm charts allow you to do several things at once at install time:

• Set the credentials to access MinIO
• Create a bucket for your backups that can be set as default

You can create a k8ssandra-medusa bucket and use minio_key/minio_secret as the credentials, and deploy MinIO in a new namespace called minio by running the following command:

helm install --set accessKey=minio_key,secretKey=minio_secret,defaultBucket.enabled=true,defaultBucket.name=k8ssandra-medusa minio minio/minio -n minio --create-namespace

After the helm install command has completed, you should see something similar to this in the minio namespace:

$ kubectl get all -n minio

NAME                        READY   STATUS    RESTARTS   AGE
pod/minio-5fd4dd687-gzr8j   1/1     Running   0          109s

NAME            TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)    AGE
service/minio   ClusterIP   10.96.144.61   <none>        9000/TCP   109s

NAME                    READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/minio   1/1     1            1           109s

NAME                              DESIRED   CURRENT   READY   AGE
replicaset.apps/minio-5fd4dd687   1         1         1       109s

Deploy Medusa

Now that MinIO is up and running, you can install Medusa and create a secret to access the bucket. Create a medusa_secret.yaml file with the following content:

apiVersion: v1
kind: Secret
metadata:
 name: medusa-bucket-key
type: Opaque
stringData:
 # Note that this currently has to be set to medusa_s3_credentials!
 medusa_s3_credentials: |-
   [default]
   aws_access_key_id = minio_key
   aws_secret_access_key = minio_secret

Now apply the file: kubectl apply -f medusa_secret.yaml

You should now see the medusa-bucket-key secret:

$ kubectl get secrets -n k8ssandra

NAME                  TYPE                                  DATA   AGE
default-token-twk5w   kubernetes.io/service-account-token   3      4m49s
medusa-bucket-key     Opaque                                1      45s

You can then deploy Medusa. Add this part to the k8ssamdra.yaml file and upgrade the deployment:

medusa:
  enabled: true
  storage: s3_compatible
  storage_properties:
      host: minio.minio.svc.cluster.local
      port: 9000
      secure: "False"
  bucketName: k8ssandra-medusa
  storageSecret: medusa-bucket-key

helm upgrade k8ssandra k8ssandra/k8ssandra -f k8ssandra.yaml

Create some data and back it up

Extract the username and password to access Cassandra into variables:

username=$(kubectl get secret k8ssandra-superuser -o jsonpath="{.data.username}" | base64 --decode)
password=$(kubectl get secret k8ssandra-superuser -o jsonpath="{.data.password}" | base64 --decode)

Connect through CQLSH on one of the nodes:

kubectl exec -it k8ssandra-dc1-default-sts-0 -c cassandra -- cqlsh -u $username -p $password

Copy/paste the following statements into the CQLSH prompt and press enter:

CREATE KEYSPACE medusa_test  WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 1};
USE medusa_test;
CREATE TABLE users (email TEXT PRIMARY KEY, name TEXT, state TEXT);
INSERT INTO users (email, name, state) VALUES ('alice@example.com', 'Alice Smith', 'TX');
INSERT INTO users (email, name, state) VALUES ('bob@example.com', 'Bob Jones', 'VA');
INSERT INTO users (email, name, state) VALUES ('carol@example.com', 'Carol Jackson', 'CA');
INSERT INTO users (email, name, state) VALUES ('david@example.com', 'David Yang', 'NV');

Check that the rows were properly inserted:

SELECT * FROM medusa_test.users;
 email             | name          | state
-------------------+---------------+-------
 alice@example.com |   Alice Smith |    TX
   bob@example.com |     Bob Jones |    VA
 david@example.com |    David Yang |    NV
 carol@example.com | Carol Jackson |    CA
(4 rows)

Now backup this data. To that end, use the following command:

helm install my-backup k8ssandra/backup --set name=backup1,cassandraDatacenter.name=dc1

Since the backup operation is asynchronous, you can monitor its completion by running the following command:

kubectl get cassandrabackup backup1 -n k8ssandra -o jsonpath={.status.finishTime}

As long as this doesn’t output a date and time, then the backup is still running. With the amount of data present and the fact that you’re using a locally accessible backend, this should complete quickly.

Deleting the data and restoring the backup

TRUNCATE the table and verify it is empty:

$ kubectl exec -it k8ssandra-dc1-default-sts-0 -n k8ssandra -c cassandra -- cqlsh -u $username -p $password

TRUNCATE medusa_test.users;
SELECT * FROM medusa_test.users;
 email | name | state
-------+------+-------
(0 rows)

Now restore the backup taken previously:

helm install restore-test k8ssandra/restore --set name=restore-backup1,backup.name=backup1,cassandraDatacenter.name=dc1

This operation will take a little longer as it requires to stop the StatefulSet pod and perform the restore as part of the init containers, before the Cassandra container can start. You can monitor progress using this command:

watch -d kubectl get cassandrarestore restore-backup1 -o jsonpath={.status} -n k8ssandra

The restore operation is fully completed once the finishTime value appears in the output:

{"finishTime":"2021-03-23T13:58:36Z","restoreKey":"83977399-44dd-4752-b4c4-407273f0339e","startTime":"2021-03-23T13:55:35Z"}

Check that you can read the data from the previously truncated table:

kubectl exec -it k8ssandra-dc1-default-sts-0 -n k8ssandra -c cassandra -- cqlsh -u $username -p $password
SELECT * FROM medusa_test.users

 email             | name          | state
-------------------+---------------+-------
 alice@example.com |   Alice Smith |    TX
   bob@example.com |     Bob Jones |    VA
 david@example.com |    David Yang |    NV
 carol@example.com | Carol Jackson |    CA
(4 rows)

You’ve successfully restored your lost data in just a few commands!

Next Step

Proceed to the Step VIII