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Using Custom Configuration File

KubeDB supports providing custom configuration for MariaDB. This tutorial will show you how to use KubeDB to run a MariaDB 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
      
    $ kubectl get ns demo
    NAME    STATUS  AGE
    demo    Active  5s
    

Note: YAML files used in this tutorial are stored in here folder in GitHub repository kubedb/docs.

Overview

MariaDB allows to configure database via configuration file. The default configuration for MariaDB can be found in /etc/mysql/my.cnf file. When MariaDB starts, it will look for custom configuration file in /etc/mysql/conf.d directory. If configuration file exist, MariaDB instance will use combined startup setting from both /etc/mysql/my.cnf and *.cnf files in /etc/mysql/conf.d directory. This custom configuration will overwrite the existing default one. To know more about configuring MariaDB see here.

At first, you have to create a config file with .cnf extension 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 MariaDB crd. KubeDB will mount this volume into /etc/mysql/conf.d directory of the database pod.

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

Custom Configuration

At first, let’s create md-config.cnf file setting max_connections and read_buffer_size parameters.

cat <<EOF > md-config.cnf
[mysqld]
max_connections = 200
read_buffer_size = 1048576
EOF

$ cat md-config.cnf
[mysqld]
max_connections = 200
read_buffer_size = 1048576

Here, read_buffer_size is set to 1MB in bytes.

Now, create a configMap with this configuration file.

$ kubectl create secret generic -n demo md-configuration --from-file=./md-config.cnf 
secret/md-configuration created

Verify the config map has the configuration file.

$ kubectl get configmap -n demo md-configuration -o yaml
apiVersion: v1
data:
  md-config.cnf: |
    [mysqld]
    max_connections = 200
    read_buffer_size = 1048576    
kind: ConfigMap
metadata:
  name: md-configuration
  namespace: demo
  ...

Now, create MariaDB crd specifying spec.configSecret field.

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2021.03.17//docs/guides/mariadb/configuration/using-config-file/examples/md-custom.yaml
mysql.kubedb.com/custom-mysql created

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

apiVersion: kubedb.com/v1alpha2
kind: MariaDB
metadata:
  name: sample-mariadb
  namespace: demo
spec:
  version: "10.5.8"
  configSecret:
    name: md-configuration
  storageType: Durable
  storage:
    storageClassName: "standard"
    accessModes:
    - ReadWriteOnce
    resources:
      requests:
        storage: 1Gi
  terminationPolicy: WipeOut

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 sample-mariadb-0 has been created.

Check that the statefulset’s pod is running

 $ kubectl get pod -n demo
NAME               READY   STATUS    RESTARTS   AGE
sample-mariadb-0   1/1     Running   0          21s

$ kubectl get mariadb -n demo 
NAME             VERSION   STATUS   AGE
sample-mariadb   10.5.8    Ready    71s

We can see the database is in ready phase so it can accept conncetion.

Now, we will check if the database has started with the custom configuration we have provided.

Read the comment written for the following commands. They contain the instructions and explanations of the commands.

# Connceting to the database
 $ kubectl exec -it -n demo sample-mariadb-0 -- bash
[email protected]:/ mysql -u${MYSQL_ROOT_USERNAME} -p${MYSQL_ROOT_PASSWORD}
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 23
Server version: 10.5.8-MariaDB-1:10.5.8+maria~focal mariadb.org binary distribution

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

# value of `max_conncetions` is same as provided 
MariaDB [(none)]> show variables like 'max_connections';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| max_connections | 200   |
+-----------------+-------+
1 row in set (0.001 sec)

# value of `read_buffer_size` is same as provided
MariaDB [(none)]> show variables like 'read_buffer_size';
+------------------+---------+
| Variable_name    | Value   |
+------------------+---------+
| read_buffer_size | 1048576 |
+------------------+---------+
1 row in set (0.001 sec)

MariaDB [(none)]> exit
Bye

Cleaning up

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

$ kubectl delete mariadb -n demo sample-mariadb
mariadb.kubedb.com "sample-mariadb" deleted
$ kubectl delete ns demo
namespace "demo" deleted