Managing MySQL Cluster Lifecycle

This guide demonstrates how to manage the lifecycle of a MySQL cluster in KubeBlocks, including stopping, starting, and restarting the cluster. Proper lifecycle management helps optimize resource usage, reduce operational costs, and ensure flexibility in your Kubernetes environment.

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.
• Namespace Preparation: To keep resources isolated, create a dedicated namespace for this tutorial:

kubectl create ns demo
namespace/demo created

Deploy a MySQL Semi-Synchronous Cluster

KubeBlocks uses a declarative approach for managing MySQL clusters. Below is an example configuration for deploying a MySQL cluster with 2 nodes (1 primary, 1 replicas) in semi-synchronous mode.

Apply the following YAML configuration to deploy the cluster:

kubectl apply -f - <<EOF
apiVersion: apps.kubeblocks.io/v1
kind: Cluster
metadata:
  name: example-mysql-cluster
  namespace: demo
spec:
  clusterDef: mysql
  topology: semisync
  terminationPolicy: Delete
  componentSpecs:
    - name: mysql
      serviceVersion: 8.0.35
      replicas: 2
      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
EOF

Verifying the Deployment

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

kubectl get cluster example-mysql-cluster -n demo -w

Example Output:

NAME                     CLUSTER-DEFINITION   TERMINATION-POLICY   STATUS    AGE
example-mysql-cluster   mysql                Delete               Creating   7s
example-mysql-cluster   mysql                Delete               Running   63s

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

Managing the Cluster Lifecycle

Stop the Cluster

Stopping the cluster terminates all its running pods but retains the persistent storage. This is useful when you want to temporarily suspend the cluster to save costs.

kubectl apply -f - <<EOF
apiVersion: operations.kubeblocks.io/v1alpha1
kind: OpsRequest
metadata:
  name: example-mysql-cluster-stop-ops
  namespace: demo
spec:
  clusterName: example-mysql-cluster
  type: Stop
EOF

kubectl patch cluster example-mysql-cluster -n demo --type='json' -p='[
  {
    "op": "add",
    "path": "/spec/componentSpecs/0/stop",
    "value": true
  }
]'

Verifying Cluster Stop

Monitor the cluster's status to ensure it transitions to the Stopped state:

kubectl get cluster -n demo -w

Example Output:

NAME                       CLUSTER-DEFINITION   TERMINATION-POLICY   STATUS     AGE
example-mysql-cluster   mysql                Delete               Stopping   93s
example-mysql-cluster   mysql                Delete               Stopped    101s

There is no Pods running in the cluster, but the persistent storage is retained.

kubectl get pods -n demo

Expected Output:

No resources found in demo namespace.

kubectl get pvc -n demo

NAME                                 STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS    VOLUMEATTRIBUTESCLASS   AGE
data-example-mysql-cluster-mysql-0   Bound    pvc-98ce87ab-acc6-4f95-8638-16e8052f98d8   20Gi       RWO            kb-default-sc   <unset>                 16m
data-example-mysql-cluster-mysql-1   Bound    pvc-5bb87b23-7c38-45de-bf04-f2822051d897   20Gi       RWO            kb-default-sc   <unset>                 16m

Start the Cluster

Starting the cluster recreates the pods and brings the cluster back online.

kubectl apply -f - <<EOF
apiVersion: operations.kubeblocks.io/v1alpha1
kind: OpsRequest
metadata:
  name: example-mysql-cluster-start-ops
  namespace: demo
spec:
  # Specifies the name of the Cluster resource that this operation is targeting.
  clusterName: example-mysql-cluster
  type: Start
EOF

kubectl patch cluster example-mysql-cluster -n demo --type='json' -p='[
  {
    "op": "remove",
    "path": "/spec/componentSpecs/0/stop"
  }
]'

Verifying Cluster Start

Monitor the cluster's status to ensure it transitions back to the Running state:

kubectl get cluster -n demo -w

Example Output:

NAME                       CLUSTER-DEFINITION   TERMINATION-POLICY   STATUS     AGE
example-mysql-cluster   mysql                Delete               Updating   5m54s
example-mysql-cluster   mysql                Delete               Running    6m6s

Restart the Cluster

Restarting the cluster allows you to recreate the pods for specific components without deleting or stopping the entire cluster.

Using OpsRequest

To restart a specific component (e.g., mysql), use the following OpsRequest:

kubectl apply -f - <<EOF
apiVersion: operations.kubeblocks.io/v1alpha1
kind: OpsRequest
metadata:
  name: example-mysql-cluster-restart-ops
  namespace: demo
spec:
  clusterName: example-mysql-cluster
  type: Restart
  restart:
  - componentName: mysql
EOF

Verifying Cluster Restart

Monitor the cluster's status to ensure the restart is completed successfully:

kubectl get opsrequest example-mysql-cluster-restart-ops -n demo -w

Expected Output:

NAME                                TYPE      CLUSTER                 STATUS    PROGRESS   AGE
example-mysql-cluster-restart-ops   Restart   example-mysql-cluster   Succeed   2/2        3m16s

Once the operation is complete, the cluster will return to the Running state.

Summary

In this guide, you learned how to:

1. Stop a MySQL cluster to suspend operations while retaining persistent storage.
2. Start a stopped cluster to bring it back online.
3. Restart specific cluster components to recreate their Pods without stopping the entire cluster.

By managing the lifecycle of your MySQL cluster, you can optimize resource utilization, reduce costs, and maintain flexibility in your Kubernetes environment. KubeBlocks provides a seamless way to perform these operations, ensuring high availability and minimal disruption.