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Horizontal Scale Postgres Cluster
This guide will show you how to use KubeDB Ops Manager to increase/decrease the number of members of a Postgres Cluster.
Before You Begin
At first, you need to have a Kubernetes cluster, and the
kubectlcommand-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
KubeDBin your cluster following the steps here.You should be familiar with the following
KubeDBconcepts:
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/guides/postgres/scaling/horizontal-scaling/scale-horizontally/yamls directory of kubedb/doc repository.
Apply Horizontal Scaling on Postgres Cluster
Here, we are going to deploy a Postgres Cluster using a supported version by KubeDB operator. Then we are going to apply horizontal scaling on it.
Prepare Cluster
At first, we are going to deploy a Cluster server with 3 members. Then, we are going to add two additional members through horizontal scaling. Finally, we will remove 1 member from the cluster again via horizontal scaling.
Find supported Postgres Version:
When you have installed KubeDB, it has created PostgresVersion CR for all supported Postgres versions. Let’s check the supported Postgres versions,
$ kubectl get postgresversion
NAME VERSION DISTRIBUTION DB_IMAGE DEPRECATED AGE
10.16 10.16 Official postgres:10.16-alpine 63s
10.16-debian 10.16 Official postgres:10.16 63s
10.19 10.19 Official postgres:10.19-bullseye 63s
10.19-bullseye 10.19 Official postgres:10.19-bullseye 63s
11.11 11.11 Official postgres:11.11-alpine 63s
11.11-debian 11.11 Official postgres:11.11 63s
11.14 11.14 Official postgres:11.14-alpine 63s
11.14-bullseye 11.14 Official postgres:11.14-bullseye 63s
11.14-bullseye-postgis 11.14 PostGIS postgis/postgis:11-3.1 63s
12.6 12.6 Official postgres:12.6-alpine 63s
12.6-debian 12.6 Official postgres:12.6 63s
12.9 12.9 Official postgres:12.9-alpine 63s
12.9-bullseye 12.9 Official postgres:12.9-bullseye 63s
12.9-bullseye-postgis 12.9 PostGIS postgis/postgis:12-3.1 63s
13.2 13.2 Official postgres:13.2-alpine 63s
13.2-debian 13.2 Official postgres:13.2 63s
13.5 13.5 Official postgres:13.5-alpine 63s
13.5-bullseye 13.5 Official postgres:13.5-bullseye 63s
13.5-bullseye-postgis 13.5 PostGIS postgis/postgis:13-3.1 63s
14.1 14.1 Official postgres:14.1-alpine 63s
14.1-bullseye 14.1 Official postgres:14.1-bullseye 63s
14.1-bullseye-postgis 14.1 PostGIS postgis/postgis:14-3.1 63s
9.6.21 9.6.21 Official postgres:9.6.21-alpine 63s
9.6.21-debian 9.6.21 Official postgres:9.6.21 63s
9.6.24 9.6.24 Official postgres:9.6.24-alpine 63s
9.6.24-bullseye 9.6.24 Official postgres:9.6.24-bullseye 63s
timescaledb-2.1.0-pg11 11.11 TimescaleDB timescale/timescaledb:2.1.0-pg11-oss 63s
timescaledb-2.1.0-pg12 12.6 TimescaleDB timescale/timescaledb:2.1.0-pg12-oss 63s
timescaledb-2.1.0-pg13 13.2 TimescaleDB timescale/timescaledb:2.1.0-pg13-oss 63s
timescaledb-2.5.0-pg14.1 14.1 TimescaleDB timescale/timescaledb:2.5.0-pg14-oss 63s
The version above that does not show DEPRECATED true is supported by KubeDB for Postgres. You can use any non-deprecated version. Here, we are going to create a Postgres Cluster using Postgres 13.2.
Deploy Postgres Cluster:
In this section, we are going to deploy a Postgres Cluster with 3 members. Then, in the next section we will scale-up the cluster using horizontal scaling. Below is the YAML of the Postgres cr that we are going to create,
apiVersion: kubedb.com/v1alpha2
kind: Postgres
metadata:
name: pg
namespace: demo
spec:
version: "13.13"
replicas: 3
standbyMode: Hot
storageType: Durable
storage:
storageClassName: "standard"
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 1Gi
terminationPolicy: WipeOut
Let’s create the Postgres cr we have shown above,
$ kubectl create -f https://github.com/kubedb/docs/raw/v2024.3.16/docs/guides/postgres/scaling/horizontal-scaling/scale-horizontally/postgres.yaml
postgres.kubedb.com/pg created
Wait for the cluster to be ready:
KubeDB operator watches for Postgres objects using Kubernetes API. When a Postgres object is created, KubeDB operator will create a new StatefulSet, Services, and Secrets, etc. A secret called pg-auth (format: {postgres-object-name}-auth) will be created storing the password for postgres superuser.
Now, watch Postgres is going to Running state and also watch StatefulSet and its pod is created and going to Running state,
$ watch -n 3 kubectl get postgres -n demo pg
Every 3.0s: kubectl get postgres -n demo pg emon-r7: Thu Dec 2 15:31:16 2021
NAME VERSION STATUS AGE
pg 13.2 Ready 4h40m
$ watch -n 3 kubectl get sts -n demo pg
Every 3.0s: kubectl get sts -n demo pg emon-r7: Thu Dec 2 15:31:38 2021
NAME READY AGE
pg 3/3 4h41m
$ watch -n 3 kubectl get pods -n demo
Every 3.0s: kubectl get pod -n demo emon-r7: Thu Dec 2 15:33:24 2021
NAME READY STATUS RESTARTS AGE
pg-0 2/2 Running 0 4h25m
pg-1 2/2 Running 0 4h26m
pg-2 2/2 Running 0 4h26m
Let’s verify that the StatefulSet’s pods have joined into cluster,
$ kubectl get secrets -n demo pg-auth -o jsonpath='{.data.\username}' | base64 -d
postgres
$ kubectl get secrets -n demo pg-auth -o jsonpath='{.data.\password}' | base64 -d
b3b5838EhjwsiuFU
So, we can see that our cluster has 3 members. Now, we are ready to apply the horizontal scale to this Postgres cluster.
Scale Up
Here, we are going to add 2 replicas in our Cluster using horizontal scaling.
Create PostgresOpsRequest:
To scale up your cluster, you have to create a PostgresOpsRequest cr with your desired number of replicas after scaling. Below is the YAML of the PostgresOpsRequest cr that we are going to create,
apiVersion: ops.kubedb.com/v1alpha1
kind: PostgresOpsRequest
metadata:
name: pg-scale-horizontal
namespace: demo
spec:
type: HorizontalScaling
databaseRef:
name: pg
horizontalScaling:
replicas: 5
Here,
spec.databaseRef.namespecifies that we are performing operation onpgPostgresdatabase.spec.typespecifies that we are performingHorizontalScalingon our database.spec.horizontalScaling.replicasspecifies the expected number of replicas after the scaling.
Let’s create the PostgresOpsRequest cr we have shown above,
$ kubectl apply -f https://github.com/kubedb/docs/raw/v2024.3.16/docs/guides/postgres/scaling/horizontal-scaling/scale-horizontally/yamls/pg-scale-up.yaml
postgresopsrequest.ops.kubedb.com/pg-scale-up created
Verify Scale-Up Succeeded:
If everything goes well, KubeDB Ops Manager will scale up the StatefulSet’s Pod. After the scaling process is completed successfully, the KubeDB Ops Manager updates the replicas of the Postgres object.
First, we will wait for PostgresOpsRequest to be successful. Run the following command to watch PostgresOpsRequest cr,
$ watch kubectl get postgresopsrequest -n demo pg-scale-up
Every 2.0s: kubectl get postgresopsrequest -n demo pg-scale-up emon-r7: Thu Dec 2 17:57:36 2021
NAME TYPE STATUS AGE
pg-scale-up HorizontalScaling Successful 8m23s
You can see from the above output that the PostgresOpsRequest has succeeded. If we describe the PostgresOpsRequest, we will see that the Postgres cluster is scaled up.
kubectl describe postgresopsrequest -n demo pg-scale-up
Name: pg-scale-up
Namespace: demo
Labels: <none>
Annotations: <none>
API Version: ops.kubedb.com/v1alpha1
Kind: PostgresOpsRequest
Metadata:
Creation Timestamp: 2021-12-02T11:49:13Z
Generation: 1
Managed Fields:
API Version: ops.kubedb.com/v1alpha1
Fields Type: FieldsV1
fieldsV1:
f:metadata:
f:annotations:
.:
f:kubectl.kubernetes.io/last-applied-configuration:
f:spec:
.:
f:databaseRef:
.:
f:name:
f:horizontalScaling:
.:
f:replicas:
f:type:
Manager: kubectl-client-side-apply
Operation: Update
Time: 2021-12-02T11:49:13Z
API Version: ops.kubedb.com/v1alpha1
Fields Type: FieldsV1
fieldsV1:
f:status:
.:
f:conditions:
f:observedGeneration:
f:phase:
Manager: kubedb-enterprise
Operation: Update
Time: 2021-12-02T11:49:13Z
Resource Version: 49610
UID: cc62fe84-5c13-4c77-b130-f748c0beff27
Spec:
Database Ref:
Name: pg
Horizontal Scaling:
Replicas: 5
Type: HorizontalScaling
Status:
Conditions:
Last Transition Time: 2021-12-02T11:49:13Z
Message: Postgres ops request is horizontally scaling database
Observed Generation: 1
Reason: Progressing
Status: True
Type: Progressing
Last Transition Time: 2021-12-02T11:50:38Z
Message: Successfully Horizontally Scaled Up
Observed Generation: 1
Reason: ScalingUp
Status: True
Type: ScalingUp
Last Transition Time: 2021-12-02T11:50:38Z
Message: Successfully Horizontally Scaled Postgres
Observed Generation: 1
Reason: Successful
Status: True
Type: Successful
Observed Generation: 1
Phase: Successful
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal PauseDatabase 10m KubeDB Enterprise Operator Pausing Postgres demo/pg
Normal PauseDatabase 10m KubeDB Enterprise Operator Successfully paused Postgres demo/pg
Normal ScalingUp 9m17s KubeDB Enterprise Operator Successfully Horizontally Scaled Up
Normal ResumeDatabase 9m17s KubeDB Enterprise Operator Resuming PostgreSQL demo/pg
Normal ResumeDatabase 9m17s KubeDB Enterprise Operator Successfully resumed PostgreSQL demo/pg
Normal Successful 9m17s KubeDB Enterprise Operator Successfully Horizontally Scaled Database
Now, we are going to verify whether the number of members has increased to meet up the desired state. So let’s check the new pods logs to see if they have joined in the cluster as new replica.
$ kubectl logs -n demo pg-4 -c postgres -f
waiting for the role to be decided ...
running the initial script ...
Running as Replica
Attempting pg_isready on primary
Attempting query on primary
take base basebackup...
2021-12-02 11:50:11.062 GMT [17] LOG: skipping missing configuration file "/etc/config/user.conf"
2021-12-02 11:50:11.062 GMT [17] LOG: skipping missing configuration file "/etc/config/user.conf"
2021-12-02 11:50:11.075 UTC [17] LOG: starting PostgreSQL 13.2 on x86_64-pc-linux-musl, compiled by gcc (Alpine 10.2.1_pre1) 10.2.1 20201203, 64-bit
2021-12-02 11:50:11.075 UTC [17] LOG: listening on IPv4 address "0.0.0.0", port 5432
2021-12-02 11:50:11.075 UTC [17] LOG: listening on IPv6 address "::", port 5432
2021-12-02 11:50:11.081 UTC [17] LOG: listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
2021-12-02 11:50:11.088 UTC [30] LOG: database system was interrupted; last known up at 2021-12-02 11:50:10 UTC
2021-12-02 11:50:11.148 UTC [30] LOG: entering standby mode
2021-12-02 11:50:11.154 UTC [30] LOG: redo starts at 0/8000028
2021-12-02 11:50:11.157 UTC [30] LOG: consistent recovery state reached at 0/8000100
2021-12-02 11:50:11.157 UTC [17] LOG: database system is ready to accept read only connections
2021-12-02 11:50:11.162 UTC [35] LOG: started streaming WAL from primary at 0/9000000 on timeline 2
You can see above that this pod is streaming wal from primary as replica. It verifies that we have successfully scaled up.
Scale Down
Here, we are going to remove 1 replica from our cluster using horizontal scaling.
Create PostgresOpsRequest:
To scale down your cluster, you have to create a PostgresOpsRequest cr with your desired number of members after scaling. Below is the YAML of the PostgresOpsRequest cr that we are going to create,
apiVersion: ops.kubedb.com/v1alpha1
kind: PostgresOpsRequest
metadata:
name: pg-scale-down
namespace: demo
spec:
type: HorizontalScaling
databaseRef:
name: pg
horizontalScaling:
replicas: 4
Let’s create the PostgresOpsRequest cr we have shown above,
$ kubectl apply -f https://github.com/kubedb/docs/raw/v2024.3.16/docs/guides/postgres/scaling/horizontal-scaling/scale-horizontally/yamls/pg-scale-down.yaml
postgresopsrequest.ops.kubedb.com/pg-scale-down created
Verify Scale-down Succeeded:
If everything goes well, KubeDB Ops Manager will scale down the StatefulSet’s Pod. After the scaling process is completed successfully, the KubeDB Ops Manager updates the replicas of the Postgres object.
Now, we will wait for PostgresOpsRequest to be successful. Run the following command to watch PostgresOpsRequest cr,
$ watch kubectl get postgresopsrequest -n demo pg-scale-down
Every 2.0s: kubectl get postgresopsrequest -n demo pg-scale-down emon-r7: Thu Dec 2 18:15:37 2021
NAME TYPE STATUS AGE
pg-scale-down HorizontalScaling Successful 115s
You can see from the above output that the PostgresOpsRequest has succeeded. If we describe the PostgresOpsRequest, we shall see that the Postgres cluster is scaled down.
$ kubectl describe postgresopsrequest -n demo pg-scale-down
Name: pg-scale-down
Namespace: demo
Labels: <none>
Annotations: <none>
API Version: ops.kubedb.com/v1alpha1
Kind: PostgresOpsRequest
Metadata:
Creation Timestamp: 2021-12-02T12:13:42Z
Generation: 1
Managed Fields:
API Version: ops.kubedb.com/v1alpha1
Fields Type: FieldsV1
fieldsV1:
f:metadata:
f:annotations:
.:
f:kubectl.kubernetes.io/last-applied-configuration:
f:spec:
.:
f:databaseRef:
.:
f:name:
f:horizontalScaling:
.:
f:replicas:
f:type:
Manager: kubectl-client-side-apply
Operation: Update
Time: 2021-12-02T12:13:42Z
API Version: ops.kubedb.com/v1alpha1
Fields Type: FieldsV1
fieldsV1:
f:status:
.:
f:conditions:
f:observedGeneration:
f:phase:
Manager: kubedb-enterprise
Operation: Update
Time: 2021-12-02T12:13:42Z
Resource Version: 52120
UID: c69ea56e-e21c-4b1e-8a80-76f1b74ef2ba
Spec:
Database Ref:
Name: pg
Horizontal Scaling:
Replicas: 4
Type: HorizontalScaling
Status:
Conditions:
Last Transition Time: 2021-12-02T12:13:42Z
Message: Postgres ops request is horizontally scaling database
Observed Generation: 1
Reason: Progressing
Status: True
Type: Progressing
Last Transition Time: 2021-12-02T12:14:42Z
Message: Successfully Horizontally Scaled Down
Observed Generation: 1
Reason: ScalingDown
Status: True
Type: ScalingDown
Last Transition Time: 2021-12-02T12:14:42Z
Message: Successfully Horizontally Scaled Postgres
Observed Generation: 1
Reason: Successful
Status: True
Type: Successful
Observed Generation: 1
Phase: Successful
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal PauseDatabase 2m31s KubeDB Enterprise Operator Pausing Postgres demo/pg
Normal PauseDatabase 2m31s KubeDB Enterprise Operator Successfully paused Postgres demo/pg
Normal ScalingDown 91s KubeDB Enterprise Operator Successfully Horizontally Scaled Down
Normal ResumeDatabase 91s KubeDB Enterprise Operator Resuming PostgreSQL demo/pg
Normal ResumeDatabase 91s KubeDB Enterprise Operator Successfully resumed PostgreSQL demo/pg
Normal Successful 91s KubeDB Enterprise Operator Successfully Horizontally Scaled Database
Now, we are going to verify whether the number of members has decreased to meet up the desired state, Let’s check, the postgres status if it’s ready then the scale-down is successful.
$ kubectl get postgres -n demo pg
Every 3.0s: kubectl get postgres -n demo pg emon-r7: Thu Dec 2 18:16:39 2021
NAME VERSION STATUS AGE
pg 13.2 Ready 7h26m
You can see above that our Postgres cluster now has a total of 4 members. It verifies that we have successfully scaled down.
Cleaning Up
To clean up the Kubernetes resources created by this tutorial, run:
kubectl delete pg -n demo pg
kubectl delete postgresopsrequest -n demo pg-scale-up
kubectl delete postgresopsrequest -n demo pg-scale-down