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Reconfigure Postgres Cluster Database

This guide will show you how to use KubeDB Enterprise operator to reconfigure a Postgres Cluster.

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 and Enterprise operator in your cluster following the steps here.

• You should be familiar with the following KubeDB concepts:

  • Postgres
  • PostgresOpsRequest
  • Reconfigure Overview

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

$ kubectl create ns demo
namespace/demo created

Now, we are going to deploy a Postgres Cluster using a supported version by KubeDB operator. Then we are going to apply PostgresOpsRequest to reconfigure its configuration.

Prepare Postgres Cluster

Now, we are going to deploy a Postgres Cluster database with version 16.1.

Deploy Postgres

At first, we will create user.conf file containing required configuration settings. To know more about this configuration file, check here

$ cat user.conf
max_connections=200
shared_buffers=256MB

Now, we will create a secret with this configuration file.

$ kubectl create secret generic -n demo pg-configuration --from-file=./user.conf
secret/pg-configuration created

In this section, we are going to create a Postgres object specifying spec.configSecret field to apply this custom configuration. Below is the YAML of the Postgres CR that we are going to create,

apiVersion: kubedb.com/v1
kind: Postgres
metadata:
  name: ha-postgres
  namespace: demo
spec:
  version: "16.1"
  replicas: 3
  configSecret:
    name: pg-configuration
  storageType: Durable
  storage:
    storageClassName: "standard"
    accessModes:
    - ReadWriteOnce
    resources:
      requests:
        storage: 1Gi
  deletionPolicy: WipeOut

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

$ kubectl create -f https://github.com/kubedb/docs/raw/v2024.11.18/docs/examples/postgres/reconfigure/ha-postgres.yaml
postgres.kubedb.com/ha-postgres created

Now, wait until ha-postgres has status Ready. i.e,

$ kubectl get pods,pg -n demo
NAME                READY   STATUS    RESTARTS   AGE
pod/ha-postgres-0   2/2     Running   0          2m28s
pod/ha-postgres-1   2/2     Running   0          59s
pod/ha-postgres-2   2/2     Running   0          51s

NAME                              VERSION   STATUS   AGE
postgres.kubedb.com/ha-postgres   16.1      Ready    2m38s

Now lets check these parameters,

$ kubectl exec -it -n demo ha-postgres-0 -- bash
Defaulted container "postgres" out of: postgres, pg-coordinator, postgres-init-container (init)
ha-postgres-0:/$ psql
psql (16.1)
Type "help" for help.

postgres=# show max_connections;
 max_connections 
-----------------
 200
(1 row)

postgres=# show shared_buffers;
 shared_buffers 
----------------
 256MB
(1 row)

You can check the other pods same way. So we have configured custom parameters.

Reconfigure using new config secret

Now we will reconfigure this database to set max_connections to 250.

Now, we will create new file user.conf containing required configuration settings.

$ cat user.conf 
max_connections = 250

Then, we will create a new secret with this configuration file.

$ kubectl create secret generic -n demo new-pg-configuration --from-file=./user.conf
secret/new-pg-configuration created

Create PostgresOpsRequest

Now, we will use this secret to replace the previous secret using a PostgresOpsRequest CR. The PostgresOpsRequest yaml is given below,

apiVersion: ops.kubedb.com/v1alpha1
kind: PostgresOpsRequest
metadata:
  name: pgops-reconfigure-config
  namespace: demo
spec:
  type: Reconfigure
  databaseRef:
    name: ha-postgres
  configuration:   
    configSecret:
      name: new-pg-configuration

Here,

• spec.databaseRef.name specifies that we are reconfiguring ha-postgres database.
• spec.type specifies that we are performing Reconfigure on our database.
• spec.configuration.configSecret.name specifies the name of the new secret.

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

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2024.11.18/docs/examples/postgres/reconfigure/reconfigure-using-secret.yaml
postgresopsrequest.ops.kubedb.com/pgops-reconfigure-config created

Verify the new configuration is working

If everything goes well, KubeDB Enterprise operator will update the configSecret of Postgres object.

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

$ kubectl get pgops -n demo
NAME                       TYPE          STATUS       AGE
pgops-reconfigure-config   Reconfigure   Successful   3m21s

We can see from the above output that the PostgresOpsRequest has succeeded. Now let’s connect to a postgres instance and run a postgres internal command to check the new configuration we have provided.

$ kubectl exec -it -n demo ha-postgres-0 -- bash
Defaulted container "postgres" out of: postgres, pg-coordinator, postgres-init-container (init)
ha-postgres-0:/$ psql
psql (16.1)
Type "help" for help.

postgres=# show max_connections;
 max_connections 
-----------------
 250
(1 row)

As we can see from the configuration has changed, the value of max_connections has been changed from 200 to 250. You can check for other pods in the same way.

Reconfigure Existing Config Secret

Now, we will create a new PostgresOpsRequest to reconfigure our existing secret new-pg-configuration by modifying our user.conf file using applyConfig. The PostgresOpsRequest yaml is given below,

apiVersion: ops.kubedb.com/v1alpha1
kind: PostgresOpsRequest
metadata:
  name: pgops-reconfigure-apply-config
  namespace: demo
spec:
  type: Reconfigure
  databaseRef:
    name: ha-postgres
  configuration:
    applyConfig:
      user.conf: |
        max_connections = 230
        shared_buffers = 512MB        

Note: You can modify multiple fields of your current configuration using applyConfig. If you don’t have any secrets then applyConfig will create a secret for you. Here, we modified value of our two existing fields which are max_connections and shared_buffers.

Here,

• spec.databaseRef.name specifies that we are reconfiguring ha-postgres database.
• spec.type specifies that we are performing Reconfigure on our database.
• spec.configuration.applyConfig contains the configuration of existing or newly created secret.

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2024.11.18/docs/examples/postgres/reconfigure/apply-config.yaml
postgresopsrequest.ops.kubedb.com/pgops-reconfigure-apply-config created

Verify the new configuration is working

If everything goes well, KubeDB Enterprise operator will update the configSecret of Postgres object.

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

$ kubectl get postgresopsrequest pgops-reconfigure-apply-config -n demo
NAME            TYPE          STATUS       AGE
apply-config   Reconfigure   Successful   4m59s

We can see this ops request was successful.

Now let’s connect to a postgres instance and run a postgres internal command to check the new configuration we have provided.

$ kubectl exec -it -n demo ha-postgres-0 -- bash
Defaulted container "postgres" out of: postgres, pg-coordinator, postgres-init-container (init)
ha-postgres-0:/$ cat /etc/config/user.conf 
#________******kubedb.com/inline-config******________#
max_connections=230
shared_buffers=512MB
ha-postgres-0:/$ 
ha-postgres-0:/$ 
ha-postgres-0:/$ psql
psql (16.1)
Type "help" for help.

postgres=# show max_connections;
 max_connections 
-----------------
 230
(1 row)

postgres=# show shared_buffers;
 shared_buffers 
----------------
 512MB
(1 row)

As we can see from above the configuration has been changed, the value of max_connections has been changed from 250 to 230 and the shared_buffers has been changed 256MB to 512MB.

Remove Custom Configuration

We can also remove exisiting custom config using PostgresOpsRequest. Provide true to field spec.configuration.removeCustomConfig and make an Ops Request to remove existing custom configuration.

Create PostgresOpsRequest

Lets create an PostgresOpsRequest having spec.configuration.removeCustomConfig is equal true,

apiVersion: ops.kubedb.com/v1alpha1
kind: PostgresOpsRequest
metadata:
  name: remove-config
  namespace: demo
spec:
  type: Reconfigure
  databaseRef:
    name: ha-postgres
  configuration:   
    removeCustomConfig: true

Here,

• spec.databaseRef.name specifies that we are reconfiguring remove-config database.
• spec.type specifies that we are performing Reconfigure on our database.
• spec.configuration.removeCustomConfig is a bool field that should be true when you want to remove existing custom configuration.

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

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2024.11.18/docs/examples/postgres/reconfigure/remove-config.yaml
postgresopsrequest.ops.kubedb.com/remove-config created

Verify the new configuration is working

If everything goes well, KubeDB Enterprise operator will update the configSecret of Postgres object.

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

$ kubectl get pgops -n demo remove-config 
NAME            TYPE          STATUS       AGE
remove-config   Reconfigure   Successful   5m5s

Now let’s connect to a postgres instance and run a postgres internal command to check the new configuration we have provided.

$ kubectl exec -it -n demo ha-postgres-0 -- bash
Defaulted container "postgres" out of: postgres, pg-coordinator, postgres-init-container (init)
ha-postgres-0:/$ psql
psql (16.1)
Type "help" for help.

postgres=# show max_connections;
 max_connections 
-----------------
 100
(1 row)

postgres=# show shared_buffers;
 shared_buffers 
----------------
 256MB
(1 row)

As we can see from the configuration has changed to its default value. So removal of existing custom configuration using PostgresOpsRequest is successful.

Cleaning Up

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

$ kubectl delete postgres -n demo ha-postgres
$ kubectl delete postgresopsrequest -n demo pgops-reconfigure-apply-config pgops-reconfigure-config remove-config
$ kubectl delete ns demo

Next Steps

• Detail concepts of Postgres object.
• Monitor your Postgres database with KubeDB using out-of-the-box Prometheus operator.
• Monitor your Postgres database with KubeDB using out-of-the-box builtin-Prometheus.
• Use private Docker registry to deploy Postgres with KubeDB.
• Use kubedb cli to manage databases like kubectl for Kubernetes.
• Detail concepts of Postgres object.
• Want to hack on KubeDB? Check our contribution guidelines.