Deploying a MongoDB ReplicaSet Cluster with KubeBlocks

A ReplicaSet provides high availability with one primary and multiple secondary replicas. Data is replicated asynchronously from the primary to the secondaries.

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

Deploying the MongoDB ReplicaSet 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: mongodb-replicaset
  namespace: demo
spec:
  terminationPolicy: Delete
  clusterDef: mongodb
  topology: replicaset
  componentSpecs:
    - name: mongodb
      serviceVersion: 6.0.27
      replicas: 3
      disableExporter: false
      resources:
        limits:
          cpu: "0.5"
          memory: "0.5Gi"
        requests:
          cpu: "0.5"
          memory: "0.5Gi"
      volumeClaimTemplates:
        - name: data
          spec:
            accessModes:
              - ReadWriteOnce
            resources:
              requests:
                storage: 20Gi

Key Configuration Details:

• clusterDef: mongodb: Specifies the ClusterDefinition CR for the cluster.
• topology: replicaset: Configures the cluster to use replicaset topology.
• componentSpecs: Defines the components in the cluster

Verifying the Deployment

Check the Cluster Status

Once the cluster is deployed, check its status:

kubectl get cluster mongodb-replicaset -n demo -w

Example Output:

NAME                CLUSTER-DEFINITION   TERMINATION-POLICY   STATUS     AGE
mongodb-replicaset  mongodb              Delete               Creating   40s
mongodb-replicaset  mongodb              Delete               Creating   71s
mongodb-replicaset  mongodb              Delete               Creating   71s
mongodb-replicaset  mongodb              Delete               Updating   71s
mongodb-replicaset  mongodb              Delete               Running    2m55s

Verify Component and Pod Status

kubectl get component -n demo -l app.kubernetes.io/instance=mongodb-replicaset
kubectl get pod -n demo -l app.kubernetes.io/instance=mongodb-replicaset -L kubeblocks.io/role

Example Output:

NAME                       DEFINITION                        SERVICE-VERSION   STATUS    AGE
mongodb-replicaset-mongodb mongodb-replicaset-1.0.0          6.0.27            Running   3m5s
NAME                         READY   STATUS    RESTARTS   AGE
NAME                           READY   STATUS    RESTARTS   AGE     ROLE
mongodb-replicaset-mongodb-0   4/4     Running   0          3m7s    primary
mongodb-replicaset-mongodb-1   4/4     Running   0          2m13s   secondary
mongodb-replicaset-mongodb-2   4/4     Running   0          119s    secondary

Cleanup

To remove all resources created during this tutorial:

kubectl delete cluster mongodb-replicaset -n demo
kubectl delete ns demo