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CONFIGURATION.md

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Configuration

Note

This documentation applies to mariadb-operator version >= v0.0.28

This documentation aims to provide guidance on various configuration aspects across many mariadb-operator CRs.

Table of contents

my.cnf

An inline configuration file (my.cnf) can be provisioned in the MariaDB resource via the myCnf field:

apiVersion: k8s.mariadb.com/v1alpha1
kind: MariaDB
metadata:
  name: mariadb
spec:
  ...
  myCnf: |
    [mariadb]
    bind-address=*
    default_storage_engine=InnoDB
    binlog_format=row
    innodb_autoinc_lock_mode=2
    innodb_buffer_pool_size=1024M
    max_allowed_packet=256M

In this field, you may provide any configuration option or system variable supported by MariaDB.

Under the hood, the operator automatically creates a ConfigMap with the contents of the myCnf field, which will be mounted in the MariaDB instance. Alternatively, you can manage your own configuration using a pre-existing ConfigMap by linking it via myCnfConfigMapKeyRef:

apiVersion: k8s.mariadb.com/v1alpha1
kind: MariaDB
metadata:
  name: mariadb
spec:
  ...
  myCnfConfigMapKeyRef:
    name: mariadb
    key: mycnf

To ensure your configuration changes take effect, the operator triggers a rolling update whenever the myCnf field or a ConfigMap is updated. For the operator to detect changes in a ConfigMap, it must be labeled with k8s.mariadb.com/watch. Refer to the external resources section for further detail.

Passwords

Some CRs require passwords provided as Secret references to function properly. For instance, the root password for a MariaDB resource:

apiVersion: k8s.mariadb.com/v1alpha1
kind: MariaDB
metadata:
  name: mariadb-galera
spec:
  rootPasswordSecretKeyRef:
    name: mariadb
    key: root-password

By default, fields like rootPasswordSecretKeyRef are optional and defaulted by the operator, resulting in random password generation if not provided:

apiVersion: k8s.mariadb.com/v1alpha1
kind: MariaDB
metadata:
  name: mariadb-galera
spec:
  rootPasswordSecretKeyRef:
    name: mariadb
    key: root-password
    generate: true

You may choose to explicitly provide a Secret reference via rootPasswordSecretKeyRef and opt-out from random password generation by either not providing the generate field or setting it to false:

apiVersion: k8s.mariadb.com/v1alpha1
kind: MariaDB
metadata:
  name: mariadb-galera
spec:
  rootPasswordSecretKeyRef:
    name: mariadb
    key: root-password
    generate: false

This way, we are telling the operator that we are expecting a Secret to be available eventually, enabling the use of GitOps tools to seed the password:

  • sealed-secrets: The Secret is reconciled from a SealedSecret, which is decrypted by the sealed-secrets controller.
  • external-secrets: The Secret is reconciled fom an ExternalSecret, which is read by the external-secrets controller from an external secrets source (Vault, AWS Secrets Manager ...).

External resources

Many CRs have a references to external resources (i.e. ConfigMap, Secret) not managed by the operator.

apiVersion: k8s.mariadb.com/v1alpha1
kind: MariaDB
metadata:
  name: mariadb
spec:
  ...
  myCnfConfigMapKeyRef:
    name: mariadb
    key: mycnf

These external resources should be labeled with k8s.mariadb.com/watch so the operator can watch them and perform reconciliations based on their changes. For example, see the my.cnf ConfigMap:

apiVersion: v1
kind: ConfigMap
metadata:
  name: mariadb
  labels:
    k8s.mariadb.com/watch: ""
data:
  my.cnf: |
    [mariadb]
    bind-address=*
    default_storage_engine=InnoDB
    binlog_format=row
    innodb_autoinc_lock_mode=2
    innodb_buffer_pool_size=1024M
    max_allowed_packet=256M

Probes

Kubernetes probes serve as an inversion of control mechanism, enabling the application to communicate its health status to Kubernetes. This enables Kubernetes to take appropriate actions when the application is unhealthy, such as restarting or stop sending traffic to Pods.

Important

Make sure you check the Kubernetes documentation if you are unfamiliar with Kubernetes probes.

Fine tunning of probes for databases running in Kubernetes is critical, you may do so by tweaking the following fields:

apiVersion: k8s.mariadb.com/v1alpha1
kind: MariaDB
metadata:
  name: mariadb-galera
spec:
  livenessProbe:
    initialDelaySeconds: 20
    periodSeconds: 5
    timeoutSeconds: 5

  readinessProbe:
    initialDelaySeconds: 20
    periodSeconds: 5
    timeoutSeconds: 5

There isn't an universally correct default value for these thresholds, so we recommend determining your own based on factors like the compute resources, network, storage, and other aspects of the environment where your MariaDB and MaxScale instances are running.