Setting Up a MongoDB Cluster with Scheduled Backups in KubeBlocks

This guide demonstrates how to deploy a MongoDB cluster using KubeBlocks and configure scheduled backups with retention in an S3 repository.

Prerequisites

Before proceeding, ensure the following:

• Environment Setup:
  • A Kubernetes cluster is up and running.
  • The kubectl CLI tool is configured to communicate with your cluster.
  • KubeBlocks CLI and KubeBlocks Operator are installed. Follow the installation instructions here.
• Namespace Preparation: To keep resources isolated, create a dedicated namespace for this tutorial:

kubectl create ns demo
namespace/demo created

Deploy a MongoDB Cluster

KubeBlocks uses a declarative approach for managing MongoDB Replication Clusters. Below is an example configuration for deploying a MongoDB ReplicaSet Cluster with one primary replica and two secondary replicas.

Apply the following YAML configuration to deploy the cluster:

apiVersion: apps.kubeblocks.io/v1
kind: Cluster
metadata:
  name: mongo-cluster
  namespace: demo
spec:
  terminationPolicy: Delete
  clusterDef: mongodb
  topology: replicaset
  componentSpecs:
    - name: mongodb
      serviceVersion: "6.0.16"
      replicas: 3
      resources:
        limits:
          cpu: '0.5'
          memory: 0.5Gi
        requests:
          cpu: '0.5'
          memory: 0.5Gi
      volumeClaimTemplates:
        - name: data
          spec:
            storageClassName: ""
            accessModes:
              - ReadWriteOnce
            resources:
              requests:
                storage: 20Gi

Verifying the Deployment

Monitor the cluster status until it transitions to the Running state:

kubectl get cluster mongo-cluster -n demo -w

Expected Output:

kubectl get cluster mongo-cluster -n demo
NAME            CLUSTER-DEFINITION   TERMINATION-POLICY   STATUS     AGE
mongo-cluster   mongodb              Delete               Creating   49s
mongo-cluster   mongodb              Delete               Running    62s

Check the pod status and roles:

kubectl get pods -l app.kubernetes.io/instance=mongo-cluster -L  kubeblocks.io/role -n demo

Expected Output:

NAME                      READY   STATUS    RESTARTS   AGE   ROLE
mongo-cluster-mongodb-0   2/2     Running   0          78s   primary
mongo-cluster-mongodb-1   2/2     Running   0          63s   secondary
mongo-cluster-mongodb-2   2/2     Running   0          48s   secondary

Once the cluster status becomes Running, your MongoDB cluster is ready for use.

Prerequisites for Backup

1. Backup Repository Configured:

   • Configured BackupRepo
   • Network connectivity between cluster and repo, BackupRepo status is Ready

2. Cluster is Running:

   • Cluster must be in Running state
   • No ongoing operations (scaling, upgrades etc.)

Configure Scheduled Backups

KubeBlocks automatically creates a BackupSchedule resource when the cluster is created. Follow these steps to enable and configure scheduled backups:

1. Verify the default backup schedule configuration:

kubectl get backupschedule mongo-cluster-mongodb-backup-schedule  -n demo -oyaml

Example Output:

apiVersion: dataprotection.kubeblocks.io/v1alpha1
kind: BackupSchedule
spec:
  backupPolicyName: mongo-cluster-MongoDB-backup-policy
  schedules:
  - backupMethod: datafile
    # ┌───────────── minute (0-59)
    # │ ┌───────────── hour (0-23)
    # │ │ ┌───────────── day of month (1-31)
    # │ │ │ ┌───────────── month (1-12)
    # │ │ │ │ ┌───────────── day of week (0-6) (Sunday=0)
    # │ │ │ │ │
    # 0 18 * * *
    # schedule this job every day at 6:00 PM (18:00).
    cronExpression: 0 18 * * * # update the cronExpression to your need
    enabled: true # set to `true` to schedule base backup periodically
    retentionPeriod: 7d # set the retention period to your need

2. Enable and customize the backup schedule:

kubectl edit backupschedule mongo-cluster-mongodb-backup-schedule -n demo

Update these key parameters:

• enabled: Set to true to activate scheduled backups
• cronExpression: Configure backup frequency using cron syntax
• retentionPeriod: Set how long to keep backups (e.g., 7d, 1mo)

Example configuration for daily backups at 6PM UTC with 7-day retention:

schedules:
- backupMethod: datafile
  enabled: true
  cronExpression: "0 18 * * *"
  retentionPeriod: 7d

3. Verify the schedule configuration:

# Check schedule status
kubectl get backupschedule mongo-cluster-mongodb-backup-schedule -n demo -w

# View detailed configuration
kubectl describe backupschedule mongo-cluster-mongodb-backup-schedule -n demo

Monitoring and Managing Backups

After enabling scheduled backups, monitor their execution and manage backup retention:

1. View all backups:

kubectl get backup -n demo -l app.kubernetes.io/instance=mongo-cluster

2. Inspect backup details:

kubectl describe backup <backup-name> -n demo

3. Verify backup artifacts:

• Status should show "Completed"
• Check backup size matches expectations
• Confirm retention period is being applied
• Validate backup files exist in repository

4. Manage backup retention:

• To manually delete old backups:

kubectl delete backup <backup-name> -n demo

• To modify retention period:

kubectl edit backupschedule mongo-cluster-mongodb-backup-schedule -n demo

Cleanup

To remove all created resources, delete the MongoDB cluster along with its namespace:

kubectl delete cluster mongo-cluster -n demo
kubectl delete ns demo

Summary

This guide demonstrated:

1. Configuration of automated MongoDB backups
2. Schedule customization using cron syntax
3. Retention policy management
4. Backup verification procedures

Your MongoDB cluster now has:

• Regular automated backups
• Configurable retention policies
• Complete backup history tracking