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Autoscaling the Compute Resource of a Pgpool

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

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 Provisioner, Ops-manager and Autoscaler operator in your cluster following the steps here.
Install Metrics Server 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

Note: YAML files used in this tutorial are stored in docs/examples/pgpool directory of kubedb/docs repository.

Autoscaling of Pgpool

Prepare Postgres

Prepare a KubeDB Postgres cluster using this tutorial, or you can use any externally managed postgres but in that case you need to create an appbinding yourself. In this tutorial we will use 3 node Postgres cluster named ha-postgres.

Here, we are going to deploy a Pgpool standalone using a supported version by KubeDB operator. Then we are going to apply PgpoolAutoscaler to set up autoscaling.

Deploy Pgpool

In this section, we are going to deploy a Pgpool with version 4.5.0 Then, in the next section we will set up autoscaling for this pgpool using PgpoolAutoscaler CRD. Below is the YAML of the Pgpool CR that we are going to create,

apiVersion: kubedb.com/v1alpha2
kind: Pgpool
metadata:
  name: pgpool-autoscale
  namespace: demo
spec:
  version: "4.5.0"
  replicas: 1
  postgresRef:
    name: ha-postgres
    namespace: demo
  podTemplate:
    spec:
      containers:
        - name: pgpool
          resources:
            requests:
              cpu: "200m"
              memory: "300Mi"
            limits:
              cpu: "200m"
              memory: "300Mi"
  deletionPolicy: WipeOut

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

$ kubectl create -f https://github.com/kubedb/docs/raw/v2024.8.21/docs/examples/pgpool/autoscaling/compute/pgpool-autoscale.yaml
pgpool.kubedb.com/pgpool-autoscale created

Now, wait until pgpool-autoscale has status Ready. i.e,

$ kubectl get pp -n demo
NAME               TYPE                  VERSION   STATUS   AGE
pgpool-autoscale   kubedb.com/v1alpha2   4.5.0     Ready    22s

Let’s check the Pod containers resources,

$ kubectl get pod -n demo pgpool-autoscale-0 -o json | jq '.spec.containers[].resources'
{
  "limits": {
    "cpu": "200m",
    "memory": "300Mi"
  },
  "requests": {
    "cpu": "200m",
    "memory": "300Mi"
  }
}

Let’s check the Pgpool resources,

$ kubectl get pgpool -n demo pgpool-autoscale -o json | jq '.spec.podTemplate.spec.containers[0].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 pgpool.

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

Compute Resource Autoscaling

Here, we are going to set up compute (cpu and memory) autoscaling using a PgpoolAutoscaler Object.

Create PgpoolAutoscaler Object

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

apiVersion: autoscaling.kubedb.com/v1alpha1
kind: PgpoolAutoscaler
metadata:
  name: pgpool-autoscale-ops
  namespace: demo
spec:
  databaseRef:
    name: pgpool-autoscale
  compute:
    pgpool:
      trigger: "On"
      podLifeTimeThreshold: 5m
      resourceDiffPercentage: 20
      minAllowed:
        cpu: 400m
        memory: 400Mi
      maxAllowed:
        cpu: 1
        memory: 1Gi
      controlledResources: ["cpu", "memory"]
      containerControlledValues: "RequestsAndLimits"

Here,

spec.databaseRef.name specifies that we are performing compute resource autoscaling on pgpool-autoscale.
spec.compute.pgpool.trigger specifies that compute resource autoscaling is enabled for this pgpool.
spec.compute.pgpool.podLifeTimeThreshold specifies the minimum lifetime for at least one of the pod to initiate a vertical scaling.
spec.compute.replicaset.resourceDiffPercentage specifies the minimum resource difference in percentage. The default is 10%. If the difference between current & recommended resource is less than ResourceDiffPercentage, Autoscaler Operator will ignore the updating.
spec.compute.pgpool.minAllowed specifies the minimum allowed resources for this pgpool.
spec.compute.pgpool.maxAllowed specifies the maximum allowed resources for this pgpool.
spec.compute.pgpool.controlledResources specifies the resources that are controlled by the autoscaler.
spec.compute.pgpool.containerControlledValues specifies which resource values should be controlled. The default is “RequestsAndLimits”.
spec.opsRequestOptions contains the options to pass to the created OpsRequest. It has 2 fields. Know more about them here : timeout, apply.

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

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2024.8.21/docs/examples/pgpool/autoscaling/compute/pgpool-autoscaler.yaml
pgpoolautoscaler.autoscaling.kubedb.com/pgpool-autoscaler-ops created

Verify Autoscaling is set up successfully

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

$ kubectl get pgpoolautoscaler -n demo
NAME                   AGE
pgpool-autoscale-ops   6m55s

$ kubectl describe pgpoolautoscaler pgpool-autoscale-ops -n demo
Name:         pgpool-autoscale-ops
Namespace:    demo
Labels:       <none>
Annotations:  <none>
API Version:  autoscaling.kubedb.com/v1alpha1
Kind:         PgpoolAutoscaler
Metadata:
  Creation Timestamp:  2024-07-17T12:09:17Z
  Generation:          1
  Resource Version:    81569
  UID:                 3841c30b-3b19-4740-82f5-bf8e257ddc18
Spec:
  Compute:
    Pgpool:
      Container Controlled Values:  RequestsAndLimits
      Controlled Resources:
        cpu
        memory
      Max Allowed:
        Cpu:     1
        Memory:  1Gi
      Min Allowed:
        Cpu:                     400m
        Memory:                  400Mi
      Pod Life Time Threshold:   5m0s
      Resource Diff Percentage:  20
      Trigger:                   On
  Database Ref:
    Name:  pgpool-autoscale
  Ops Request Options:
    Apply:  IfReady
Status:
  Checkpoints:
    Cpu Histogram:
      Bucket Weights:
        Index:              0
        Weight:             10000
      Reference Timestamp:  2024-07-17T12:10:00Z
      Total Weight:         0.8733542386168607
    First Sample Start:     2024-07-17T12:09:14Z
    Last Sample Start:      2024-07-17T12:15:06Z
    Last Update Time:       2024-07-17T12:15:38Z
    Memory Histogram:
      Bucket Weights:
        Index:              11
        Weight:             10000
      Reference Timestamp:  2024-07-17T12:15:00Z
      Total Weight:         0.7827734162991002
    Ref:
      Container Name:     pgpool
      Vpa Object Name:    pgpool-autoscale
    Total Samples Count:  6
    Version:              v3
  Conditions:
    Last Transition Time:  2024-07-17T12:10:37Z
    Message:               Successfully created PgpoolOpsRequest demo/ppops-pgpool-autoscale-zzell6
    Observed Generation:   1
    Reason:                CreateOpsRequest
    Status:                True
    Type:                  CreateOpsRequest
  Vpas:
    Conditions:
      Last Transition Time:  2024-07-17T12:09:37Z
      Status:                True
      Type:                  RecommendationProvided
    Recommendation:
      Container Recommendations:
        Container Name:  pgpool
        Lower Bound:
          Cpu:     400m
          Memory:  400Mi
        Target:
          Cpu:     400m
          Memory:  400Mi
        Uncapped Target:
          Cpu:     100m
          Memory:  262144k
        Upper Bound:
          Cpu:     1
          Memory:  1Gi
    Vpa Name:      pgpool-autoscale
Events:            <none>

So, the pgpoolautoscaler resource is created successfully.

you can see in the Status.VPAs.Recommendation section, that recommendation has been generated for our pgpool. Our autoscaler operator continuously watches the recommendation generated and creates an pgpoolopsrequest based on the recommendations, if the pgpool pods are needed to scaled up or down.

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

$ watch kubectl get pgpoolopsrequest -n demo
Every 2.0s: kubectl get pgpoolopsrequest -n demo
NAME                            TYPE              STATUS        AGE
ppops-pgpool-autoscale-zzell6   VerticalScaling   Progressing   1m48s

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

$ watch kubectl get pgpoolopsrequest -n demo
Every 2.0s: kubectl get pgpoolopsrequest -n demo
NAME                            TYPE              STATUS       AGE
ppops-pgpool-autoscale-zzell6   VerticalScaling   Successful   3m40s

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

$ kubectl describe pgpoolopsrequest -n demo ppops-pgpool-autoscale-zzell6
Name:         ppops-pgpool-autoscale-zzell6
Namespace:    demo
Labels:       app.kubernetes.io/component=connection-pooler
              app.kubernetes.io/instance=pgpool-autoscale
              app.kubernetes.io/managed-by=kubedb.com
              app.kubernetes.io/name=pgpools.kubedb.com
Annotations:  <none>
API Version:  ops.kubedb.com/v1alpha1
Kind:         PgpoolOpsRequest
Metadata:
  Creation Timestamp:  2024-07-17T12:10:37Z
  Generation:          1
  Owner References:
    API Version:           autoscaling.kubedb.com/v1alpha1
    Block Owner Deletion:  true
    Controller:            true
    Kind:                  PgpoolAutoscaler
    Name:                  pgpool-autoscale-ops
    UID:                   3841c30b-3b19-4740-82f5-bf8e257ddc18
  Resource Version:        81200
  UID:                     57f99d31-af3d-4157-aa61-0f509ec89bbd
Spec:
  Apply:  IfReady
  Database Ref:
    Name:  pgpool-autoscale
  Type:    VerticalScaling
  Vertical Scaling:
    Node:
      Resources:
        Limits:
          Cpu:     400m
          Memory:  400Mi
        Requests:
          Cpu:     400m
          Memory:  400Mi
Status:
  Conditions:
    Last Transition Time:  2024-07-17T12:10:37Z
    Message:               Pgpool ops-request has started to vertically scaling the Pgpool nodes
    Observed Generation:   1
    Reason:                VerticalScaling
    Status:                True
    Type:                  VerticalScaling
    Last Transition Time:  2024-07-17T12:10:40Z
    Message:               Successfully paused database
    Observed Generation:   1
    Reason:                DatabasePauseSucceeded
    Status:                True
    Type:                  DatabasePauseSucceeded
    Last Transition Time:  2024-07-17T12:10:40Z
    Message:               Successfully updated PetSets Resources
    Observed Generation:   1
    Reason:                UpdatePetSets
    Status:                True
    Type:                  UpdatePetSets
    Last Transition Time:  2024-07-17T12:11:25Z
    Message:               Successfully Restarted Pods With Resources
    Observed Generation:   1
    Reason:                RestartPods
    Status:                True
    Type:                  RestartPods
    Last Transition Time:  2024-07-17T12:10:45Z
    Message:               get pod; ConditionStatus:True; PodName:pgpool-autoscale-0
    Observed Generation:   1
    Status:                True
    Type:                  GetPod--pgpool-autoscale-0
    Last Transition Time:  2024-07-17T12:10:45Z
    Message:               evict pod; ConditionStatus:True; PodName:pgpool-autoscale-0
    Observed Generation:   1
    Status:                True
    Type:                  EvictPod--pgpool-autoscale-0
    Last Transition Time:  2024-07-17T12:11:20Z
    Message:               check pod running; ConditionStatus:True; PodName:pgpool-autoscale-0
    Observed Generation:   1
    Status:                True
    Type:                  CheckPodRunning--pgpool-autoscale-0
    Last Transition Time:  2024-07-17T12:11:26Z
    Message:               Successfully completed the vertical scaling for Pgpool
    Observed Generation:   1
    Reason:                Successful
    Status:                True
    Type:                  Successful
  Observed Generation:     1
  Phase:                   Successful
Events:
  Type     Reason                                                                Age    From                         Message
  ----     ------                                                                ----   ----                         -------
  Normal   Starting                                                              8m19s  KubeDB Ops-manager Operator  Start processing for PgpoolOpsRequest: demo/ppops-pgpool-autoscale-zzell6
  Normal   Starting                                                              8m19s  KubeDB Ops-manager Operator  Pausing Pgpool databse: demo/pgpool-autoscale
  Normal   Successful                                                            8m19s  KubeDB Ops-manager Operator  Successfully paused Pgpool database: demo/pgpool-autoscale for PgpoolOpsRequest: ppops-pgpool-autoscale-zzell6
  Normal   UpdatePetSets                                                         8m16s  KubeDB Ops-manager Operator  Successfully updated PetSets Resources
  Warning  get pod; ConditionStatus:True; PodName:pgpool-autoscale-0             8m11s  KubeDB Ops-manager Operator  get pod; ConditionStatus:True; PodName:pgpool-autoscale-0
  Warning  evict pod; ConditionStatus:True; PodName:pgpool-autoscale-0           8m11s  KubeDB Ops-manager Operator  evict pod; ConditionStatus:True; PodName:pgpool-autoscale-0
  Warning  check pod running; ConditionStatus:False; PodName:pgpool-autoscale-0  8m6s   KubeDB Ops-manager Operator  check pod running; ConditionStatus:False; PodName:pgpool-autoscale-0
  Warning  check pod running; ConditionStatus:True; PodName:pgpool-autoscale-0   7m36s  KubeDB Ops-manager Operator  check pod running; ConditionStatus:True; PodName:pgpool-autoscale-0
  Normal   RestartPods                                                           7m31s  KubeDB Ops-manager Operator  Successfully Restarted Pods With Resources
  Normal   Starting                                                              7m31s  KubeDB Ops-manager Operator  Resuming Pgpool database: demo/pgpool-autoscale
  Normal   Successful                                                            7m30s  KubeDB Ops-manager Operator  Successfully resumed Pgpool database: demo/pgpool-autoscale for PgpoolOpsRequest: ppops-pgpool-autoscale-zzell6

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

$ kubectl get pod -n demo pgpool-autoscale-0 -o json | jq '.spec.containers[].resources'
{
  "limits": {
    "cpu": "400m",
    "memory": "400Mi"
  },
  "requests": {
    "cpu": "400m",
    "memory": "400Mi"
  }
}

$ kubectl get pgpool -n demo pgpool-autoscale -o json | jq '.spec.podTemplate.spec.containers[0].resources'
{
  "limits": {
    "cpu": "400m",
    "memory": "400Mi"
  },
  "requests": {
    "cpu": "400m",
    "memory": "400Mi"
  }
}

The above output verifies that we have successfully auto-scaled the resources of the Pgpool.

Cleaning Up

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

kubectl delete pp -n demo pgpool-autoscale
kubectl delete pgpoolautoscaler -n demo pgpool-autoscale-ops

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