Vertical Scaling in a MySQL Cluster

This guide explains how to perform vertical scaling in a MySQL cluster managed by KubeBlocks. Vertical scaling adjusts the resource limits and requests (such as CPU and memory) allocated to the cluster components, allowing for better performance or resource optimization.

What is Vertical Scaling?

Vertical scaling involves increasing or decreasing the resources (e.g., CPU and memory) allocated to a running database cluster. Unlike horizontal scaling, which adjusts the number of replicas, vertical scaling focuses on scaling the capacity of individual Pods.

Resources that can be scaled include:

• CPU cores: Processing power for the database.
• Memory (RAM): Memory available for database operations.

KubeBlocks ensures seamless vertical scaling by carefully orchestrating Pod restarts to minimize downtime. For example:

• Secondary Pods are recreated first.
• Primary Pods are updated last to maintain cluster availability.

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 MySQL Semi-Synchronous Cluster

Deploy a 2-node semi-sync MySQL cluster (1 primary, 1 secondary):

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 status of the MySQL cluster as it is created:

kubectl get cluster -n demo -w

Example Output:

NAME                    CLUSTER-DEFINITION   TERMINATION-POLICY   STATUS     AGE
example-mysql-cluster   mysql                Delete               Creating   66s
example-mysql-cluster   mysql                Delete               Running    72s

kubectl apply -f - <<EOF
apiVersion: operations.kubeblocks.io/v1alpha1
kind: OpsRequest
metadata:
  name: example-mysql-cluster-vscale-ops
  namespace: demo
spec:
  clusterName: example-mysql-cluster
  type: VerticalScaling
  verticalScaling:
  - componentName: mysql
    requests:
      cpu: '1'
      memory: 1Gi
    limits:
      cpu: '1'
      memory: 1Gi
EOF

kubectl describe ops example-mysql-cluster-vscale-ops -n demo

Status:
  Phase:            Succeed
  Progress:         2/2
  ...

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:
        requests:
          cpu: "1"       # Update the resources to your need.
          memory: "1Gi"  # Update the resources to your need.
        limits:
          cpu: "1"       # Update the resources to your need.
          memory: "1Gi"  # Update the resources to your need.
      volumeClaimTemplates:
        - name: data
          spec:
            storageClassName: ""
            accessModes:
              - ReadWriteOnce
            resources:
              requests:
                storage: 20Gi
EOF

Verification

Verify the updated resources by inspecting the cluster configuration or Pod details:

kbcli cluster describe example-mysql-cluster -n demo

Expected Output:

Resources Allocation:
COMPONENT   INSTANCE-TEMPLATE   CPU(REQUEST/LIMIT)   MEMORY(REQUEST/LIMIT)   STORAGE-SIZE   STORAGE-CLASS
mysql                           1 / 1                1Gi / 1Gi               data:20Gi      <none>

Key Benefits of Vertical Scaling with KubeBlocks

• Seamless Scaling: Pods are recreated in a specific order to ensure minimal disruption.
• Dynamic Resource Adjustments: Easily scale CPU and memory based on workload requirements.
• Flexibility: Choose between OpsRequest for dynamic scaling or direct API updates for precise control.
• Improved Availability: The cluster remains operational during the scaling process, maintaining high availability.

Summary

In this guide, you learned how to:

1. Deploy a MySQL cluster managed by KubeBlocks.
2. Perform vertical scaling by increasing or decreasing resources for the mysql component.
3. Use both OpsRequest and direct Cluster API updates to adjust resource allocations.

Vertical scaling is a powerful tool for optimizing resource utilization and adapting to changing workload demands, ensuring your MySQL cluster remains performant and resilient.