Scale Percona Distribution for MySQL on Kubernetes¶

One of the great advantages brought by Kubernetes platform is the ease of an application scaling. Scaling an application results in adding or removing the Pods and scheduling them to available Kubernetes nodes.

Scaling can be vertical and horizontal. Vertical scaling adds more compute or storage resources to Percona Server for MySQL nodes; horizontal scaling is about adding more nodes to the cluster. High availability looks technically similar, because it also involves additional nodes, but the reason is maintaining liveness of the system in case of server or network failures.

Vertical scaling¶

Scale compute¶

There are multiple components that Operator deploys and manages: Percona Server for MySQL, Orchestrator, HAProxy or MySQL Router, etc. To add or reduce CPU or Memory you need to edit corresponding sections in the Custom Resource. We follow the structure for requests and limits that Kubernetes provides .

For example, you can add more resources to your HAProxy nodes by editing the following section in the Custom Resource:

spec:
  ...
  proxy:
    haproxy:
      ...
      resources:
        requests:
          memory: 4G
          cpu: 2
        limits:
          memory: 4G
          cpu: 2

Use our reference documentation for the Custom Resource options for more details about other components.

Scale storage¶

Kubernetes manages storage with a PersistentVolume (PV), a segment of storage supplied by the administrator, and a PersistentVolumeClaim (PVC), a request for storage from a user. In Kubernetes v1.11 the feature was added to allow a user to increase the size of an existing PVC object. The user cannot shrink the size of an existing PVC object. Certain volume types support, by default, expanding PVCs (details about PVCs and the supported volume types can be found in Kubernetes documentation )

The following are the steps to increase the size:

Extract and backup the yaml file for the cluster

kubectl get ps cluster1 -o yaml --export > CR_backup.yaml

Now you should delete the cluster.

You can use the following command to delete the cluster:
```
$ kubectl delete -f CR_backup.yaml
```

For each node, edit the yaml to resize the PVC object.

$ kubectl edit pvc datadir-cluster1-mysql-0

In the yaml, edit the spec.resources.requests.storage value.

spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 6Gi

Perform the same operation on the other nodes.

$ kubectl edit pvc datadir-cluster1-mysql-1
$ kubectl edit pvc datadir-cluster1-mysql-2

In the CR configuration file, use vim or another text editor to edit the PVC size.
```
$ vim CR_backup.yaml
```
Apply the updated configuration to the cluster.
```
$ kubectl apply -f CR_backup.yaml
```

Horizontal scaling¶

Size of the cluster is controlled by a size key in the Custom Resource options configuration. That’s why scaling the cluster needs nothing more but changing this option and applying the updated configuration file. This may be done in a specifically saved config, or on the fly, using the following command:

$ kubectl patch ps cluster1 --type='json' -p='[{"op": "replace", "path": "/spec/mysql/size", "value": 5 }]'

In this example we have changed the size of the Percona Server for MySQL Cluster to 5 instances.

Get expert help¶

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Last update: 2024-10-29