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Autoscaling the Compute Resource of a MariaDB Cluster Database

This guide will show you how to use KubeDB to autoscale compute resources i.e. cpu and memory of a MariaDB replicaset database.

Before You Begin

At first, you need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster.
Install KubeDB Community, Enterprise and Autoscaler operator in your cluster following the steps here.
Install Metrics Server from here
Install Vertical Pod Autoscaler from here
You should be familiar with the following KubeDB concepts:

To keep everything isolated, we are going to use a separate namespace called demo throughout this tutorial.

$ kubectl create ns demo
namespace/demo created

Autoscaling of Cluster Database

Here, we are going to deploy a MariaDB Cluster using a supported version by KubeDB operator. Then we are going to apply MariaDBAutoscaler to set up autoscaling.

Deploy MariaDB Cluster

In this section, we are going to deploy a MariaDB Cluster with version 10.5.8. Then, in the next section we will set up autoscaling for this database using MariaDBAutoscaler CRD. Below is the YAML of the MariaDB CR that we are going to create,

If you want to autoscale MariaDB Standalone, Just remove the spec.Replicas from the below yaml and rest of the steps are same.

apiVersion: kubedb.com/v1alpha2
kind: MariaDB
metadata:
  name: sample-mariadb
  namespace: demo
spec:
  version: "10.5.8"
  replicas: 3
  storageType: Durable
  storage:
    storageClassName: "topolvm-provisioner"
    accessModes:
    - ReadWriteOnce
    resources:
      requests: 
        storage: 1Gi
  podTemplate:
    spec:
      resources:
        requests:
          cpu: "200m"
          memory: "300Mi"
        limits:
          cpu: "200m"
          memory: "300Mi"
  terminationPolicy: WipeOut

Let’s create the MariaDB CRO we have shown above,

$ kubectl create -f https://github.com/kubedb/docs/raw/v2022.03.28/docs/guides/mariadb/autoscaler/compute/cluster/examples/sample-mariadb.yaml
mariadb.kubedb.com/sample-mariadb created

Now, wait until sample-mariadb has status Ready. i.e,

$ kubectl get mariadb -n demo
NAME             VERSION   STATUS   AGE
sample-mariadb   10.5.8    Ready    14m

Let’s check the Pod containers resources,

$ kubectl get pod -n demo sample-mariadb-0 -o json | jq '.spec.containers[].resources'
{
  "limits": {
    "cpu": "200m",
    "memory": "300Mi",
    "topolvm.cybozu.com/capacity": "1"
  },
  "requests": {
    "cpu": "200m",
    "memory": "300Mi",
    "topolvm.cybozu.com/capacity": "1"
  }
}

Let’s check the MariaDB resources,

$ kubectl get mariadb -n demo sample-mariadb -o json | jq '.spec.podTemplate.spec.resources'
{
  "limits": {
    "cpu": "200m",
    "memory": "300Mi"
  },
  "requests": {
    "cpu": "200m",
    "memory": "300Mi"
  }
}

You can see from the above outputs that the resources are same as the one we have assigned while deploying the mariadb.

We are now ready to apply the MariaDBAutoscaler CRO to set up autoscaling for this database.

Compute Resource Autoscaling

Here, we are going to set up compute resource autoscaling using a MariaDBAutoscaler Object.

Create MariaDBAutoscaler Object

In order to set up compute resource autoscaling for this database cluster, we have to create a MariaDBAutoscaler CRO with our desired configuration. Below is the YAML of the MariaDBAutoscaler object that we are going to create,

apiVersion: autoscaling.kubedb.com/v1alpha1
kind: MariaDBAutoscaler
metadata:
  name: mdas-compute
  namespace: demo
spec:
  databaseRef:
    name: sample-mariadb
  compute:
    mariadb:
      trigger: "On"
      podLifeTimeThreshold: 5m
      minAllowed:
        cpu: 250m
        memory: 350Mi
      maxAllowed:
        cpu: 1
        memory: 1Gi
      controlledResources: ["cpu", "memory"]

Here,

spec.databaseRef.name specifies that we are performing compute resource scaling operation on sample-mariadb database.
spec.compute.mariadb.trigger specifies that compute autoscaling is enabled for this database.
spec.compute.mariadb.podLifeTimeThreshold specifies the minimum lifetime for at least one of the pod to initiate a vertical scaling.
spec.compute.mariadb.minAllowed specifies the minimum allowed resources for the database.
spec.compute.mariadb.maxAllowed specifies the maximum allowed resources for the database.
spec.compute.mariadb.controlledResources specifies the resources that are controlled by the autoscaler.

Let’s create the MariaDBAutoscaler CR we have shown above,

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2022.03.28/docs/guides/mariadb/autoscaler/compute/cluster/examples/mdas-compute.yaml
mariadbautoscaler.autoscaling.kubedb.com/mdas-compute created

Verify Autoscaling is set up successfully

Let’s check that the mariadbautoscaler resource is created successfully,

$ kubectl get mariadbautoscaler -n demo
NAME           AGE
mdas-compute   5m13s

$ kubectl describe mariadbautoscaler mdas-compute -n demo
Name:         mdas-compute
Namespace:    demo
Labels:       <none>
Annotations:  <none>
API Version:  autoscaling.kubedb.com/v1alpha1
Kind:         MariaDBAutoscaler
Metadata:
  Creation Timestamp:  2022-01-13T13:05:56Z
  Generation:          1
  ...
  Resource Version:  50664
  UID:               e2f7f6cc-f2b1-46b5-88b4-2767e1a04b68
Spec:
  Compute:
    Mariadb:
      Controlled Resources:
        cpu
        memory
      Max Allowed:
        Cpu:     1
        Memory:  1Gi
      Min Allowed:
        Cpu:                    250m
        Memory:                 350Mi
      Pod Life Time Threshold:  5m
      Trigger:                  On
  Database Ref:
    Name:  sample-mariadb
Status:
  Conditions:
    Last Transition Time:  2022-01-13T13:07:05Z
    Message:               Successfully created mariaDBOpsRequest demo/mdops-vpa-sample-mariadb-z43wc8
    Observed Generation:   1
    Reason:                CreateOpsRequest
    Status:                True
    Type:                  CreateOpsRequest
Events:                    <none>

So, the mariadbautoscaler resource is created successfully.

Now, lets verify that the vertical pod autoscaler (vpa) resource is created successfully,

$ kubectl get vpa -n demo
NAME                 MODE   CPU    MEM     PROVIDED   AGE
vpa-sample-mariadb   Off    250m   350Mi   True       6m3s

$ kubectl describe vpa -n demo 
Name:         vpa-sample-mariadb
Namespace:    demo
Labels:       <none>
Annotations:  <none>
API Version:  autoscaling.k8s.io/v1
Kind:         VerticalPodAutoscaler
Metadata:
  Creation Timestamp:  2022-01-13T13:05:56Z
  Generation:          2
  ...
  Owner References:
    API Version:           autoscaling.kubedb.com/v1alpha1
    Block Owner Deletion:  true
    Controller:            true
    Kind:                  MariaDBAutoscaler
    Name:                  mdas-compute
    UID:                   e2f7f6cc-f2b1-46b5-88b4-2767e1a04b68
  Resource Version:        50458
  UID:                     5c876135-fa94-4a80-ab60-d3eb2b3fc69f
Spec:
  Resource Policy:
    Container Policies:
      Container Name:  mariadb
      Controlled Resources:
        cpu
        memory
      Controlled Values:  RequestsAndLimits
      Max Allowed:
        Cpu:     1
        Memory:  1Gi
      Min Allowed:
        Cpu:           250m
        Memory:        350Mi
      Container Name:  exporter
      Mode:            Off
      Container Name:  md-coordinator
      Mode:            Off
  Target Ref:
    API Version:  apps/v1
    Kind:         StatefulSet
    Name:         sample-mariadb
  Update Policy:
    Update Mode:  Off
Status:
  Conditions:
    Last Transition Time:  2022-01-13T13:06:13Z
    Status:                False
    Type:                  RecommendationProvided
  Recommendation:
Events:          <none>

So, we can verify from the above output that the vpa resource is created successfully. But you can see that the RecommendationProvided is false and also the Recommendation section of the vpa is empty. Let’s wait some time and describe the vpa again.

$ kubectl describe vpa vpa-sample-mariadb -n demo
Name:         vpa-sample-mariadb
Namespace:    demo
Labels:       <none>
Annotations:  <none>
API Version:  autoscaling.k8s.io/v1
Kind:         VerticalPodAutoscaler
Metadata:
  Creation Timestamp:  2021-03-06T19:10:46Z
  Generation: ...
  Owner References:
    API Version:           autoscaling.kubedb.com/v1alpha1
    Block Owner Deletion:  true
    Controller:            true
    Kind:                  MariaDBAutoscaler
    Name:                  mg-as-rs
    UID:                   9be99253-7475-43fe-a68a-34eaec3225c6
  Resource Version:        839239
  Self Link:               /apis/autoscaling.k8s.io/v1/namespaces/demo/verticalpodautoscalers/vpa-sample-mariadb
  UID:                     fd2d9896-2eee-43df-85a6-1b968f8d2862
Spec:
  Resource Policy:
    Container Policies:
      Container Name:  mariadb
      Controlled Resources:
        cpu
        memory
      Controlled Values:  RequestsAndLimits
      Max Allowed:
        Cpu:     1
        Memory:  1Gi
      Min Allowed:
        Cpu:           250m
        Memory:        350Mi
      Container Name:  replication-mode-detector
      Mode:            Off
  Target Ref:
    API Version:  apps/v1
    Kind:         StatefulSet
    Name:         sample-mariadb
  Update Policy:
    Update Mode:  Off
Status:
  Conditions:
    Last Transition Time:  2021-03-06T19:10:59Z
    Status:                True
    Type:                  RecommendationProvided
  Recommendation:
    Container Recommendations:
      Container Name:  mariadb
      Lower Bound:
        Cpu:     250m
        Memory:  350Mi
      Target:
        Cpu:     250m
        Memory:  350Mi
      Uncapped Target:
        Cpu:     182m
        Memory:  262144k
      Upper Bound:
        Cpu:     1
        Memory:  1Gi
Events:          <none>

As you can see from the output the vpa has generated a recommendation for our database. Our autoscaler operator continuously watches the recommendation generated and creates an mariadbopsrequest based on the recommendations, if the database pods are needed to scaled up or down. If you see that the RecommendationProvided is false and also the Recommendation section of the vpa is empty then wait couple of minutes and describe the vpa again.

Let’s watch the mariadbopsrequest in the demo namespace to see if any mariadbopsrequest object is created. After some time you’ll see that a mariadbopsrequest will be created based on the recommendation.

$ kubectl get mariadbopsrequest -n demo
NAME                              TYPE              STATUS       AGE
mdops-vpa-sample-mariadb-z43wc8   VerticalScaling   Progressing  11s

Let’s wait for the ops request to become successful.

$ kubectl get mariadbopsrequest -n demo
NAME                              TYPE              STATUS       AGE
mdops-vpa-sample-mariadb-z43wc8   VerticalScaling   Successful   2m32s

We can see from the above output that the MariaDBOpsRequest has succeeded. If we describe the MariaDBOpsRequest we will get an overview of the steps that were followed to scale the database.

$ kubectl describe mariadbopsrequest -n demo mdops-vpa-sample-mariadb-z43wc8
Name:         mdops-vpa-sample-mariadb-z43wc8
Namespace:    demo
Labels:       app.kubernetes.io/component=database
              app.kubernetes.io/instance=sample-mariadb
              app.kubernetes.io/managed-by=kubedb.com
              app.kubernetes.io/name=mariadbs.kubedb.com
Annotations:  <none>
API Version:  ops.kubedb.com/v1alpha1
Kind:         MariaDBOpsRequest
Metadata:
  Creation Timestamp:  2022-01-13T13:07:05Z
  Generation:          1
  ...
  Owner References:
    API Version:           autoscaling.kubedb.com/v1alpha1
    Block Owner Deletion:  true
    Controller:            true
    Kind:                  MariaDBAutoscaler
    Name:                  mdas-compute
    UID:                   e2f7f6cc-f2b1-46b5-88b4-2767e1a04b68
  Resource Version:        51793
  UID:                     15338f3d-b394-4276-bbd0-52bbf771d06b
Spec:
  Database Ref:
    Name:  sample-mariadb
  Type:    VerticalScaling
  Vertical Scaling:
    Mariadb:
      Limits:
        Cpu:     250m
        Memory:  350Mi
      Requests:
        Cpu:     250m
        Memory:  350Mi
Status:
  Conditions:
    Last Transition Time:  2022-01-13T13:07:05Z
    Message:               Controller has started to Progress the MariaDBOpsRequest: demo/mdops-vpa-sample-mariadb-z43wc8
    Observed Generation:   1
    Reason:                OpsRequestProgressingStarted
    Status:                True
    Type:                  Progressing
    Last Transition Time:  2022-01-13T13:07:05Z
    Message:               Vertical scaling started in MariaDB: demo/sample-mariadb for MariaDBOpsRequest: mdops-vpa-sample-mariadb-z43wc8
    Observed Generation:   1
    Reason:                VerticalScalingStarted
    Status:                True
    Type:                  Scaling
    Last Transition Time:  2022-01-13T13:11:11Z
    Message:               Vertical scaling performed successfully in MariaDB: demo/sample-mariadb for MariaDBOpsRequest: mdops-vpa-sample-mariadb-z43wc8
    Observed Generation:   1
    Reason:                SuccessfullyPerformedVerticalScaling
    Status:                True
    Type:                  VerticalScaling
    Last Transition Time:  2022-01-13T13:11:11Z
    Message:               Controller has successfully scaled the MariaDB demo/mdops-vpa-sample-mariadb-z43wc8
    Observed Generation:   1
    Reason:                OpsRequestProcessedSuccessfully
    Status:                True
    Type:                  Successful
  Observed Generation:     3
  Phase:                   Successful
...

Now, we are going to verify from the Pod, and the MariaDB yaml whether the resources of the replicaset database has updated to meet up the desired state, Let’s check,

$ kubectl get pod -n demo sample-mariadb-0 -o json | jq '.spec.containers[].resources'
{
  "limits": {
    "cpu": "250m",
    "memory": "350Mi"
  },
  "requests": {
    "cpu": "250m",
    "memory": "350Mi"
  }
}

$ kubectl get mariadb -n demo sample-mariadb -o json | jq '.spec.podTemplate.spec.resources'
{
  "limits": {
    "cpu": "250m",
    "memory": "350Mi"
  },
  "requests": {
    "cpu": "250m",
    "memory": "350Mi"
  }
}

The above output verifies that we have successfully auto scaled the resources of the MariaDB replicaset database.

Cleaning Up

To clean up the Kubernetes resources created by this tutorial, run:

kubectl delete mariadb -n demo sample-mariadb
kubectl delete mariadbautoscaler -n demo mdas-compute
kubectl delete ns demo

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