Backup and restore Cassandra data
Medusa is a Cassandra backup and restore tool. It’s packaged with K8ssandra Operator and supports a variety of backends.
These instructions use a local minio bucket as an example.
Supported object storage types for backups
Supported in K8ssandra Operator’s Medusa:
- local
- s3
- s3_compatible
- s3_rgw
- azure_blobs
- google_storage
Deploying Medusa
You can deploy Medusa on all Cassandra datacenters in the cluster through the addition of settings in the K8ssandraCluster definition. Example:
apiVersion: k8ssandra.io/v1alpha1
kind: K8ssandraCluster
metadata:
name: demo
spec:
cassandra:
...
...
medusa:
storageProperties:
# Can be either of local, google_storage, azure_blobs, s3, s3_compatible, s3_rgw or ibm_storage
storageProvider: s3_compatible
# Name of the secret containing the credentials file to access the backup storage backend
storageSecretRef:
name: medusa-bucket-key
# Name of the storage bucket
bucketName: k8ssandra-medusa
# Prefix for this cluster in the storage bucket directory structure, used for multitenancy
prefix: test
# Host to connect to the storage backend (Omitted for GCS, S3, Azure and local).
host: minio.minio.svc.cluster.local
# Port to connect to the storage backend (Omitted for GCS, S3, Azure and local).
port: 9000
# Region of the storage bucket
# region: us-east-1
# Whether or not to use SSL to connect to the storage backend
secure: false
# Maximum backup age that the purge process should observe.
# 0 equals unlimited
# maxBackupAge: 0
# Maximum number of backups to keep (used by the purge process).
# 0 equals unlimited
# maxBackupCount: 0
# AWS Profile to use for authentication.
# apiProfile:
# transferMaxBandwidth: 50MB/s
# Number of concurrent uploads.
# Helps maximizing the speed of uploads but puts more pressure on the network.
# Defaults to 1.
# concurrentTransfers: 1
# File size in bytes over which cloud specific cli tools are used for transfer.
# Defaults to 100 MB.
# multiPartUploadThreshold: 104857600
# Age after which orphan sstables can be deleted from the storage backend.
# Protects from race conditions between purge and ongoing backups.
# Defaults to 10 days.
# backupGracePeriodInDays: 10
# Pod storage settings to use for local storage (testing only)
# podStorage:
# storageClassName: standard
# accessModes:
# - ReadWriteOnce
# size: 100Mi
The definition above requires a medusa-bucket-key to be created in the target namespace before the K8ssandraCluster object gets created. Use the following format for this secret:
apiVersion: v1
kind: Secret
metadata:
name: medusa-bucket-key
type: Opaque
stringData:
# Note that this currently has to be set to credentials!
credentials: |-
[default]
aws_access_key_id = minio_key
aws_secret_access_key = minio_secret
The file should always specify credentials as shown in the example above; in that section, provide the expected format and credential values that are expected by Medusa for the chosen storage backend. For more, refer to the Medusa documentation to know which file format should used for each supported storage backend.
A successful deployment should inject a new init container named medusa-restore and a new container named medusa in the Cassandra STS pods.
Creating a Backup
To perform a backup of a Cassandra datacenter, create the following custom resource in the namespace where K8ssandra was deployed:
apiVersion: medusa.k8ssandra.io/v1alpha1
kind: CassandraBackup
metadata:
name: medusa-backup1
spec:
cassandraDatacenter: dc1
name: medusa-backup1
The metadata.name value can match the spec.name value for convenience, but it is not mandatory. The latter will be used to identify the backup in the storage backend, the former being the name of the CassandraBackup custom resource in Kubernetes.
Checking Backup Completion
K8ssandra Operator will detect the CassandraBackup object creation and trigger a backup asynchronously.
To monitor the backup completion, check if the finishTime value isn’t empty in the CassandraBackup object status. Example:
% kubectl get cassandrabackup/medusa-backup1 -o yaml
kind: CassandraBackup
metadata:
name: medusa-backup1
spec:
backupType: differential
cassandraDatacenter: dc1
name: medusa-backup1
status:
...
...
finishTime: "2022-01-06T16:34:35Z"
finished:
- demo-dc1-default-sts-0
- demo-dc1-default-sts-1
- demo-dc1-default-sts-2
startTime: "2022-01-06T16:34:30Z"
All pods having completed the backup will be in the finished list.
Restoring a Backup
To restore an existing backup for a Cassandra datacenter, create the following custom resource in the namespace where K8ssandra was deployed. Example:
apiVersion: medusa.k8ssandra.io/v1alpha1
kind: CassandraRestore
metadata:
name: restore-backup1
namespace: k8ssandra-operator
spec:
cassandraDatacenter:
name: dc1
clusterName: demo
backup: medusa-backup1
inPlace: true
shutdown: true
The spec.backup value should match the CassandraBackup spec.name value.
Once the K8ssandra Operator detects on the CassandraRestore object creation, it will control the shutdown of all Cassandra pods, and the medusa-restore container will perform the actual data restore upon pod restart.
Checking Restore Completion
To monitor the restore completion, check if the finishTime value isn’t empty in the CassandraRestore object status. Example:
% kubectl get cassandrarestore/restore-backup1 -o yaml
apiVersion: medusa.k8ssandra.io/v1alpha1
kind: CassandraRestore
metadata:
name: restore-backup1
spec:
backup: medusa-backup1
cassandraDatacenter:
clusterName: demo
name: dc1
inPlace: true
shutdown: true
status:
datacenterStopped: "2022-01-06T16:45:09Z"
finishTime: "2022-01-06T16:48:23Z"
restoreKey: ec5b35c1-f2fe-4465-a74f-e29aa1d467ff
startTime: "2022-01-06T16:44:53Z"
Next steps
See the following Custom Resource Definition (CRD) reference topics:
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