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Using Custom Configuration File

KubeDB supports providing custom configuration for PostgreSQL. This tutorial will show you how to use KubeDB to run PostgreSQL database with custom configuration.

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.

Now, install KubeDB cli on your workstation and KubeDB operator in your cluster following the steps here.

To keep things isolated, this tutorial uses 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/postgres folder in GitHub repository kubedb/docs.


PostgreSQL allows to configure database via Configuration File, SQL and Shell. The most common way is to edit configuration file postgresql.conf. When PostgreSQL docker image starts, it uses the configuration specified in postgresql.conf file. This file can have include directive which allows to include configuration from other files. One of these include directives is include_if_exists which accept a file reference. If the referenced file exists, it includes configuration from the file. Otherwise, it uses default configuration. KubeDB takes advantage of this feature to allow users to provide their custom configuration. To know more about configuring PostgreSQL see here.

At first, you have to create a config file named user.conf with your desired configuration. Then you have to put this file into a volume. You have to specify this volume in spec.configSecret section while creating Postgres crd. KubeDB will mount this volume into /etc/config/ directory of the database pod which will be referenced by include_if_exists directive.

In this tutorial, we will configure max_connections and shared_buffers via a custom config file. We will use Secret as volume source.

Custom Configuration

At first, let’s create user.conf file setting max_connections and shared_buffers parameters.

$ cat user.conf

Note that config file name must be user.conf

Now, create a Secret with this configuration file.

$ kubectl create secret generic -n demo pg-configuration --from-literal=user.conf="$(curl -fsSL"
secret/pg-configuration created

Verify the Secret has the configuration file.

$ kubectl get secret -n demo pg-configuration -o yaml
apiVersion: v1
  user.conf: |-
kind: Secret
  creationTimestamp: "2019-02-07T12:08:26Z"
  name: pg-configuration
  namespace: demo
  resourceVersion: "44214"
  selfLink: /api/v1/namespaces/demo/secrets/pg-configuration
  uid: 131b321f-2ad1-11e9-9d44-080027154f61

Now, create Postgres crd specifying spec.configSecret field.

$ kubectl apply -f created

Below is the YAML for the Postgres crd we just created.

kind: Postgres
  name: custom-postgres
  namespace: demo
  version: "13.2"
    name: pg-configuration
    storageClassName: "standard"
    - ReadWriteOnce
        storage: 1Gi

Now, wait a few minutes. KubeDB operator will create necessary PVC, statefulset, services, secret etc. If everything goes well, we will see that a pod with the name custom-postgres-0 has been created.

Check that the statefulset’s pod is running

$ kubectl get pod -n demo custom-postgres-0
NAME                READY     STATUS    RESTARTS   AGE
custom-postgres-0   1/1       Running   0          14m

Check the pod’s log to see if the database is ready

$ kubectl logs -f -n demo custom-postgres-0
I0705 12:05:51.697190       1 logs.go:19] FLAG: --alsologtostderr="false"
I0705 12:05:51.717485       1 logs.go:19] FLAG: --enable-analytics="true"
I0705 12:05:51.717543       1 logs.go:19] FLAG: --help="false"
I0705 12:05:51.717558       1 logs.go:19] FLAG: --log_backtrace_at=":0"
I0705 12:05:51.717566       1 logs.go:19] FLAG: --log_dir=""
I0705 12:05:51.717573       1 logs.go:19] FLAG: --logtostderr="false"
I0705 12:05:51.717581       1 logs.go:19] FLAG: --stderrthreshold="0"
I0705 12:05:51.717589       1 logs.go:19] FLAG: --v="0"
I0705 12:05:51.717597       1 logs.go:19] FLAG: --vmodule=""
We want "custom-postgres-0" as our leader
I0705 12:05:52.753464       1 leaderelection.go:175] attempting to acquire leader lease  demo/custom-postgres-leader-lock...
I0705 12:05:52.822093       1 leaderelection.go:184] successfully acquired lease demo/custom-postgres-leader-lock
Got leadership, now do your jobs
Running as Primary
sh: locale: not found

WARNING: enabling "trust" authentication for local connections
You can change this by editing pg_hba.conf or using the option -A, or
--auth-local and --auth-host, the next time you run initdb.
/scripts/primary/ ignoring /var/initdb/*

LOG:  database system was shut down at 2018-07-05 12:07:51 UTC
LOG:  MultiXact member wraparound protections are now enabled
LOG:  database system is ready to accept connections
LOG:  autovacuum launcher started

Once we see LOG: database system is ready to accept connections in the log, the database is ready.

Now, we will check if the database has started with the custom configuration we have provided. We will exec into the pod and use SHOW query to check the run-time parameters.

 $ kubectl exec -it -n demo custom-postgres-0 sh
 / #
 ## login as user "postgres". no authentication required from inside the pod because it is using trust authentication local connection.
/ # psql -U postgres
psql (9.6.7)
Type "help" for help.

## query for "max_connections"
postgres=# SHOW max_connections;
(1 row)

## query for "shared_buffers"
postgres=# SHOW shared_buffers;
(1 row)

## log out from database
postgres=# \q
/ #

You can also connect to this database from pgAdmin and use following SQL query to check these configuration.

SELECT name,setting
FROM pg_settings
WHERE name='max_connections' OR name='shared_buffers';

Cleaning up

To cleanup the Kubernetes resources created by this tutorial, run:

kubectl patch -n demo pg/custom-postgres -p '{"spec":{"terminationPolicy":"WipeOut"}}' --type="merge"
kubectl delete -n demo pg/custom-postgres

kubectl delete -n demo secret pg-configuration
kubectl delete ns demo

If you would like to uninstall KubeDB operator, please follow the steps here.

Next Steps