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New to KubeDB? Please start here.

Horizontal Scale Pgpool

This guide will show you how to use KubeDB Ops-manager operator to scale the replicaset 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. If you do not already have a cluster, you can create one by using kind.

  • Install KubeDB Provisioner and Ops-manager operator in your cluster following the steps 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.

Apply Horizontal Scaling on pgpool

Here, we are going to deploy a Pgpool using a supported version by KubeDB operator. Then we are going to apply horizontal scaling on it.

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.

Prepare Pgpool

Now, we are going to deploy a Pgpool with version 4.5.0.

Deploy Pgpool

In this section, we are going to deploy a Pgpool. Then, in the next section we will scale the pgpool using PgpoolOpsRequest CRD. Below is the YAML of the Pgpool CR that we are going to create,

apiVersion: kubedb.com/v1alpha2
kind: Pgpool
metadata:
  name: pp-horizontal
  namespace: demo
spec:
  version: "4.5.0"
  replicas: 1
  postgresRef:
    name: ha-postgres
    namespace: demo
  initConfig:
    pgpoolConfig:
      max_pool : 60
  deletionPolicy: WipeOut

Here we are creating the pgpool with max_pool=60, it is necessary because we will up scale the pgpool replicas so for that we need larger max_pool. Let’s create the Pgpool CR we have shown above,

$ kubectl create -f https://github.com/kubedb/docs/raw/v2024.8.21/docs/examples/pgpool/scaling/pp-horizontal.yaml
pgpool.kubedb.com/pp-horizontal created

Now, wait until pp-horizontal has status Ready. i.e,

$ kubectl get pp -n demo
NAME            TYPE                  VERSION   STATUS   AGE
pp-horizontal   kubedb.com/v1alpha2   4.5.0     Ready    2m

Let’s check the number of replicas this pgpool has from the Pgpool object, number of pods the petset have,

$ kubectl get pgpool -n demo pp-horizontal -o json | jq '.spec.replicas'
1

$ kubectl get petset -n demo pp-horizontal -o json | jq '.spec.replicas'
1

We can see from both command that the pgpool has 3 replicas.

We are now ready to apply the PgpoolOpsRequest CR to scale this pgpool.

Scale Up Replicas

Here, we are going to scale up the replicas of the pgpool to meet the desired number of replicas after scaling.

Create PgpoolOpsRequest

In order to scale up the replicas of the pgpool, we have to create a PgpoolOpsRequest CR with our desired replicas. Below is the YAML of the PgpoolOpsRequest CR that we are going to create,

apiVersion: ops.kubedb.com/v1alpha1
kind: PgpoolOpsRequest
metadata:
  name: pgpool-horizontal-scale-up
  namespace: demo
spec:
  type: HorizontalScaling
  databaseRef:
    name: pp-horizontal
  horizontalScaling:
    node: 3

Here,

  • spec.databaseRef.name specifies that we are performing horizontal scaling operation on pp-horizontal pgpool.
  • spec.type specifies that we are performing HorizontalScaling on our pgpool.
  • spec.horizontalScaling.replicas specifies the desired replicas after scaling.

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

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2024.8.21/docs/examples/pgpool/scaling/horizontal-scaling/ppops-hscale-up-ops.yaml
pgpoolopsrequest.ops.kubedb.com/pgpool-horizontal-scale-up created

Verify replicas scaled up successfully

If everything goes well, KubeDB Ops-manager operator will update the replicas of Pgpool object and related PetSet.

Let’s wait for PgpoolOpsRequest to be Successful. Run the following command to watch PgpoolOpsRequest CR,

$ watch kubectl get pgpoolopsrequest -n demo
Every 2.0s: kubectl get pgpoolopsrequest -n demo
NAME                         TYPE                STATUS       AGE
pgpool-horizontal-scale-up   HorizontalScaling   Successful   2m49s

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 pgpool-horizontal-scale-up
Name:         pgpool-horizontal-scale-up
Namespace:    demo
Labels:       <none>
Annotations:  <none>
API Version:  ops.kubedb.com/v1alpha1
Kind:         PgpoolOpsRequest
Metadata:
  Creation Timestamp:  2024-07-17T08:35:13Z
  Generation:          1
  Resource Version:    62002
  UID:                 ce44f7a1-e78d-4248-a691-62fe1efd11f3
Spec:
  Apply:  IfReady
  Database Ref:
    Name:  pp-horizontal
  Horizontal Scaling:
    Node:  3
  Type:    HorizontalScaling
Status:
  Conditions:
    Last Transition Time:  2024-07-17T08:35:13Z
    Message:               Pgpool ops-request has started to horizontally scaling the nodes
    Observed Generation:   1
    Reason:                HorizontalScaling
    Status:                True
    Type:                  HorizontalScaling
    Last Transition Time:  2024-07-17T08:35:16Z
    Message:               Successfully paused database
    Observed Generation:   1
    Reason:                DatabasePauseSucceeded
    Status:                True
    Type:                  DatabasePauseSucceeded
    Last Transition Time:  2024-07-17T08:35:41Z
    Message:               Successfully Scaled Up Node
    Observed Generation:   1
    Reason:                HorizontalScaleUp
    Status:                True
    Type:                  HorizontalScaleUp
    Last Transition Time:  2024-07-17T08:35:21Z
    Message:               patch petset; ConditionStatus:True; PodName:pp-horizontal-1
    Observed Generation:   1
    Status:                True
    Type:                  PatchPetset--pp-horizontal-1
    Last Transition Time:  2024-07-17T08:35:26Z
    Message:               is pod ready; ConditionStatus:True; PodName:pp-horizontal-1
    Observed Generation:   1
    Status:                True
    Type:                  IsPodReady--pp-horizontal-1
    Last Transition Time:  2024-07-17T08:35:26Z
    Message:               client failure; ConditionStatus:True; PodName:pp-horizontal-1
    Observed Generation:   1
    Status:                True
    Type:                  ClientFailure--pp-horizontal-1
    Last Transition Time:  2024-07-17T08:35:26Z
    Message:               is node healthy; ConditionStatus:True; PodName:pp-horizontal-1
    Observed Generation:   1
    Status:                True
    Type:                  IsNodeHealthy--pp-horizontal-1
    Last Transition Time:  2024-07-17T08:35:31Z
    Message:               patch petset; ConditionStatus:True; PodName:pp-horizontal-2
    Observed Generation:   1
    Status:                True
    Type:                  PatchPetset--pp-horizontal-2
    Last Transition Time:  2024-07-17T08:35:31Z
    Message:               pp-horizontal already has desired replicas
    Observed Generation:   1
    Reason:                HorizontalScale
    Status:                True
    Type:                  HorizontalScale
    Last Transition Time:  2024-07-17T08:35:36Z
    Message:               is pod ready; ConditionStatus:True; PodName:pp-horizontal-2
    Observed Generation:   1
    Status:                True
    Type:                  IsPodReady--pp-horizontal-2
    Last Transition Time:  2024-07-17T08:35:36Z
    Message:               client failure; ConditionStatus:True; PodName:pp-horizontal-2
    Observed Generation:   1
    Status:                True
    Type:                  ClientFailure--pp-horizontal-2
    Last Transition Time:  2024-07-17T08:35:36Z
    Message:               is node healthy; ConditionStatus:True; PodName:pp-horizontal-2
    Observed Generation:   1
    Status:                True
    Type:                  IsNodeHealthy--pp-horizontal-2
    Last Transition Time:  2024-07-17T08:35:41Z
    Message:               Successfully updated Pgpool
    Observed Generation:   1
    Reason:                UpdateDatabase
    Status:                True
    Type:                  UpdateDatabase
    Last Transition Time:  2024-07-17T08:35:41Z
    Message:               Successfully completed horizontally scale pgpool cluster
    Observed Generation:   1
    Reason:                Successful
    Status:                True
    Type:                  Successful
  Observed Generation:     1
  Phase:                   Successful
Events:
  Type     Reason                                                          Age    From                         Message
  ----     ------                                                          ----   ----                         -------
  Normal   Starting                                                        4m5s   KubeDB Ops-manager Operator  Start processing for PgpoolOpsRequest: demo/pgpool-horizontal-scale-up
  Normal   Starting                                                        4m5s   KubeDB Ops-manager Operator  Pausing Pgpool databse: demo/pp-horizontal
  Normal   Successful                                                      4m5s   KubeDB Ops-manager Operator  Successfully paused Pgpool database: demo/pp-horizontal for PgpoolOpsRequest: pgpool-horizontal-scale-up
  Normal   patch petset; ConditionStatus:True; PodName:pp-horizontal-1     3m57s  KubeDB Ops-manager Operator  patch petset; ConditionStatus:True; PodName:pp-horizontal-1
  Normal   is pod ready; ConditionStatus:True; PodName:pp-horizontal-1     3m52s  KubeDB Ops-manager Operator  is pod ready; ConditionStatus:True; PodName:pp-horizontal-1
  Normal   is node healthy; ConditionStatus:True; PodName:pp-horizontal-1  3m52s  KubeDB Ops-manager Operator  is node healthy; ConditionStatus:True; PodName:pp-horizontal-1
  Normal   patch petset; ConditionStatus:True; PodName:pp-horizontal-2     3m47s  KubeDB Ops-manager Operator  patch petset; ConditionStatus:True; PodName:pp-horizontal-2
  Normal   is pod ready; ConditionStatus:True; PodName:pp-horizontal-2     3m42s  KubeDB Ops-manager Operator  is pod ready; ConditionStatus:True; PodName:pp-horizontal-2
  Normal   is node healthy; ConditionStatus:True; PodName:pp-horizontal-2  3m42s  KubeDB Ops-manager Operator  is node healthy; ConditionStatus:True; PodName:pp-horizontal-2
  Normal   HorizontalScaleUp                                               3m37s  KubeDB Ops-manager Operator  Successfully Scaled Up Node
  Normal   UpdateDatabase                                                  3m37s  KubeDB Ops-manager Operator  Successfully updated Pgpool
  Normal   Starting                                                        3m37s  KubeDB Ops-manager Operator  Resuming Pgpool database: demo/pp-horizontal
  Normal   Successful                                                      3m37s  KubeDB Ops-manager Operator  Successfully resumed Pgpool database: demo/pp-horizontal for PgpoolOpsRequest: pgpool-horizontal-scale-up

Now, we are going to verify the number of replicas this pgpool has from the Pgpool object, number of pods the petset have,

$ kubectl get pp -n demo pp-horizontal -o json | jq '.spec.replicas'
3

$ kubectl get petset -n demo pp-horizontal -o json | jq '.spec.replicas'
3

From all the above outputs we can see that the replicas of the pgpool is 3. That means we have successfully scaled up the replicas of the Pgpool.

Scale Down Replicas

Here, we are going to scale down the replicas of the pgpool to meet the desired number of replicas after scaling.

Create PgpoolOpsRequest

In order to scale down the replicas of the pgpool, we have to create a PgpoolOpsRequest CR with our desired replicas. Below is the YAML of the PgpoolOpsRequest CR that we are going to create,

apiVersion: ops.kubedb.com/v1alpha1
kind: PgpoolOpsRequest
metadata:
  name: pgpool-horizontal-scale-down
  namespace: demo
spec:
  type: HorizontalScaling
  databaseRef:
    name: pp-horizontal
  horizontalScaling:
    node: 2

Here,

  • spec.databaseRef.name specifies that we are performing horizontal scaling down operation on pp-horizontal pgpool.
  • spec.type specifies that we are performing HorizontalScaling on our pgpool.
  • spec.horizontalScaling.replicas specifies the desired replicas after scaling.

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

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2024.8.21/docs/examples/pgpool/scaling/horizontal-scaling/ppops-hscale-down-ops.yaml
pgpoolopsrequest.ops.kubedb.com/pgpool-horizontal-scale-down created

Verify replicas scaled down successfully

If everything goes well, KubeDB Ops-manager operator will update the replicas of Pgpool object and related PetSet.

Let’s wait for PgpoolOpsRequest to be Successful. Run the following command to watch PgpoolOpsRequest CR,

$ watch kubectl get pgpoolopsrequest -n demo
Every 2.0s: kubectl get pgpoolopsrequest -n demo
NAME                           TYPE                STATUS       AGE
pgpool-horizontal-scale-down   HorizontalScaling   Successful   75s

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 pgpool-horizontal-scale-down
Name:         pgpool-horizontal-scale-down
Namespace:    demo
Labels:       <none>
Annotations:  <none>
API Version:  ops.kubedb.com/v1alpha1
Kind:         PgpoolOpsRequest
Metadata:
  Creation Timestamp:  2024-07-17T08:52:28Z
  Generation:          1
  Resource Version:    63600
  UID:                 019f9d8f-c2b0-4154-b3d3-b715b8805fd7
Spec:
  Apply:  IfReady
  Database Ref:
    Name:  pp-horizontal
  Horizontal Scaling:
    Node:  2
  Type:    HorizontalScaling
Status:
  Conditions:
    Last Transition Time:  2024-07-17T08:52:28Z
    Message:               Pgpool ops-request has started to horizontally scaling the nodes
    Observed Generation:   1
    Reason:                HorizontalScaling
    Status:                True
    Type:                  HorizontalScaling
    Last Transition Time:  2024-07-17T08:52:31Z
    Message:               Successfully paused database
    Observed Generation:   1
    Reason:                DatabasePauseSucceeded
    Status:                True
    Type:                  DatabasePauseSucceeded
    Last Transition Time:  2024-07-17T08:53:16Z
    Message:               Successfully Scaled Down Node
    Observed Generation:   1
    Reason:                HorizontalScaleDown
    Status:                True
    Type:                  HorizontalScaleDown
    Last Transition Time:  2024-07-17T08:52:36Z
    Message:               patch petset; ConditionStatus:True; PodName:pp-horizontal-2
    Observed Generation:   1
    Status:                True
    Type:                  PatchPetset--pp-horizontal-2
    Last Transition Time:  2024-07-17T08:52:36Z
    Message:               pp-horizontal already has desired replicas
    Observed Generation:   1
    Reason:                HorizontalScale
    Status:                True
    Type:                  HorizontalScale
    Last Transition Time:  2024-07-17T08:52:41Z
    Message:               get pod; ConditionStatus:False
    Observed Generation:   1
    Status:                False
    Type:                  GetPod
    Last Transition Time:  2024-07-17T08:53:11Z
    Message:               get pod; ConditionStatus:True; PodName:pp-horizontal-2
    Observed Generation:   1
    Status:                True
    Type:                  GetPod--pp-horizontal-2
    Last Transition Time:  2024-07-17T08:53:16Z
    Message:               Successfully updated Pgpool
    Observed Generation:   1
    Reason:                UpdateDatabase
    Status:                True
    Type:                  UpdateDatabase
    Last Transition Time:  2024-07-17T08:53:16Z
    Message:               Successfully completed horizontally scale pgpool cluster
    Observed Generation:   1
    Reason:                Successful
    Status:                True
    Type:                  Successful
  Observed Generation:     1
  Phase:                   Successful
Events:
  Type     Reason                                                       Age   From                         Message
  ----     ------                                                       ----  ----                         -------
  Normal   Starting                                                     96s   KubeDB Ops-manager Operator  Start processing for PgpoolOpsRequest: demo/pgpool-horizontal-scale-down
  Normal   Starting                                                     96s   KubeDB Ops-manager Operator  Pausing Pgpool databse: demo/pp-horizontal
  Normal   Successful                                                   96s   KubeDB Ops-manager Operator  Successfully paused Pgpool database: demo/pp-horizontal for PgpoolOpsRequest: pgpool-horizontal-scale-down
  Normal   patch petset; ConditionStatus:True; PodName:pp-horizontal-2  88s   KubeDB Ops-manager Operator  patch petset; ConditionStatus:True; PodName:pp-horizontal-2
  Normal   get pod; ConditionStatus:False                               83s   KubeDB Ops-manager Operator  get pod; ConditionStatus:False
  Normal   get pod; ConditionStatus:True; PodName:pp-horizontal-2       53s   KubeDB Ops-manager Operator  get pod; ConditionStatus:True; PodName:pp-horizontal-2
  Normal   HorizontalScaleDown                                          48s   KubeDB Ops-manager Operator  Successfully Scaled Down Node
  Normal   UpdateDatabase                                               48s   KubeDB Ops-manager Operator  Successfully updated Pgpool
  Normal   Starting                                                     48s   KubeDB Ops-manager Operator  Resuming Pgpool database: demo/pp-horizontal
  Normal   Successful                                                   48s   KubeDB Ops-manager Operator  Successfully resumed Pgpool database: demo/pp-horizontal for PgpoolOpsRequest: pgpool-horizontal-scale-down

Now, we are going to verify the number of replicas this pgpool has from the Pgpool object, number of pods the petset have,

$ kubectl get pp -n demo pp-horizontal -o json | jq '.spec.replicas'
2

$ kubectl get petset -n demo pp-horizontal -o json | jq '.spec.replicas'
2

From all the above outputs we can see that the replicas of the pgpool is 2. That means we have successfully scaled up the replicas of the Pgpool.

Cleaning Up

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

kubectl delete mg -n pp-horizontal
kubectl delete pgpoolopsrequest -n demo pgpool-horizontal-scale-down

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