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MariaDB

What is MariaDB

MariaDB is a Kubernetes Custom Resource Definitions (CRD). It provides declarative configuration for MariaDB in a Kubernetes native way. You only need to describe the desired database configuration in a MariaDB object, and the KubeDB operator will create Kubernetes objects in the desired state for you.

MariaDB Spec

As with all other Kubernetes objects, a MariaDB needs apiVersion, kind, and metadata fields. It also needs a .spec section. Below is an example MariaDB object.

apiVersion: kubedb.com/v1alpha2
kind: MariaDB
metadata:
  name: sample-mariadb
  namespace: demo
spec:
  authSecret:
    name: sample-mariadb-auth
  monitor:
    agent: prometheus.io
    prometheus:
      exporter:
        port: 56790
        resources: {}
      serviceMonitor:
        interval: 10s
        labels:
          k8s-app: prometheus
  podTemplate:
    controller: {}
    metadata: {}
    spec:
      affinity:
        podAntiAffinity:
          preferredDuringSchedulingIgnoredDuringExecution:
          - podAffinityTerm:
              labelSelector:
                matchLabels:
                  app.kubernetes.io/instance: sample-mariadb
                  app.kubernetes.io/managed-by: kubedb.com
                  app.kubernetes.io/name: mariadbs.kubedb.com
              namespaces:
              - demo
              topologyKey: kubernetes.io/hostname
            weight: 100
          - podAffinityTerm:
              labelSelector:
                matchLabels:
                  app.kubernetes.io/instance: sample-mariadb
                  app.kubernetes.io/managed-by: kubedb.com
                  app.kubernetes.io/name: mariadbs.kubedb.com
              namespaces:
              - demo
              topologyKey: failure-domain.beta.kubernetes.io/zone
            weight: 50
      resources:
        limits:
          cpu: 500m
          memory: 1Gi
        requests:
          cpu: 500m
          memory: 1Gi
      serviceAccountName: sample-mariadb
  replicas: 3
  requireSSL: true
  storage:
    accessModes:
    - ReadWriteOnce
    resources:
      requests:
        storage: 1Gi
    storageClassName: standard
  storageType: Durable
  terminationPolicy: WipeOut
  tls:
    certificates:
    - alias: server
      dnsNames:
      - localhost
      ipAddresses:
      - 127.0.0.1
      secretName: sample-mariadb-server-cert
      subject:
        organizations:
        - kubedb:server
    - alias: archiver
      secretName: sample-mariadb-archiver-cert
    - alias: metrics-exporter
      secretName: sample-mariadb-metrics-exporter-cert
    issuerRef:
      apiGroup: cert-manager.io
      kind: Issuer
      name: md-issuer
  version: 10.5.8

spec.version

spec.version is a required field specifying the name of the MariaDBVersion crd where the docker images are specified. Currently, when you install KubeDB, it creates the following MariaDBVersion resources,

  • 10.5.8, 10.4.17

spec.authSecret

spec.authSecret is an optional field that points to a Secret used to hold credentials for mariadb root user. If not set, the KubeDB operator creates a new Secret {mariadb-object-name}-auth for storing the password for mariadb root user for each MariaDB object. If you want to use an existing secret please specify that when creating the MariaDB object using spec.authSecret.name.

This secret contains a user key and a password key which contains the username and password respectively for mariadb root user. Here, the value of user key is fixed to be root.

Secrets provided by users are not managed by KubeDB, and therefore, won’t be modified or garbage collected by the KubeDB operator (version 0.13.0 and higher).

Example:

kubectl create secret generic mariadb-auth -n demo \
    --from-literal=user=root \
    --from-literal=password=6q8u_2jMOW-OOZXk
secret/mariadb-auth created
apiVersion: v1
data:
  password: NnE4dV8yak1PVy1PT1pYaw==
  user: cm9vdA==
kind: Secret
metadata:
  name: mariadb-auth
  namespace: demo
type: Opaque

spec.storageType

spec.storageType is an optional field that specifies the type of storage to use for the database. It can be either Durable or Ephemeral. The default value of this field is Durable. If Ephemeral is used then KubeDB will create MariaDB database using emptyDir volume. In this case, you don’t have to specify spec.storage field.

spec.storage

If you set spec.storageType: to Durable, then spec.storage is a required field that specifies the StorageClass of PVCs dynamically allocated to store data for the database. This storage spec will be passed to the StatefulSet created by KubeDB operator to run database pods. You can specify any StorageClass available in your cluster with appropriate resource requests.

  • spec.storage.storageClassName is the name of the StorageClass used to provision PVCs. PVCs don’t necessarily have to request a class. A PVC with its storageClassName set equal to "" is always interpreted to be requesting a PV with no class, so it can only be bound to PVs with no class (no annotation or one set equal to “"). A PVC with no storageClassName is not quite the same and is treated differently by the cluster depending on whether the DefaultStorageClass admission plugin is turned on.
  • spec.storage.accessModes uses the same conventions as Kubernetes PVCs when requesting storage with specific access modes.
  • spec.storage.resources can be used to request specific quantities of storage. This follows the same resource model used by PVCs.

To learn how to configure spec.storage, please visit the links below:

spec.init

spec.init is an optional section that can be used to initialize a newly created MariaDB database. MariaDB databases can be initialized in one of two ways:

  • Initialize from Script
  • Initialize from Stash Restore

Initialize via Script

To initialize a MariaDB database using a script (shell script, sql script, etc.), set the spec.init.script section when creating a MariaDB object. It will execute files alphabetically with extensions .sh , .sql and .sql.gz that is found in the repository. The scripts inside child folders will be skipped. script must have the following information:

Below is an example showing how a script from a configMap can be used to initialize a MariaDB database.

apiVersion: kubedb.com/v1alpha2
kind: MariaDB
metadata:
  name: sample-mariadb
  namespace: demo
spec:
  version: 10.5.8
  init:
    script:
      configMap:
        name: md-init-script

In the above example, KubeDB operator will launch a Job to execute all js script of md-init-script in alphabetical order once StatefulSet pods are running.

spec.monitor

MariaDB managed by KubeDB can be monitored with builtin-Prometheus and Prometheus operator out-of-the-box.

spec.requireSSL

spec.requireSSL specifies whether the client connections require SSL. If spec.requireSSL is true then the server permits only TCP/IP connections that use SSL, or connections that use a socket file (on Unix) or shared memory (on Windows). The server rejects any non-secure connection attempt. For more details, please visit here

spec.tls

spec.tls specifies the TLS/SSL configurations for the MariaDB.

The following fields are configurable in the spec.tls section:

  • issuerRef is a reference to the Issuer or ClusterIssuer CR of cert-manager that will be used by KubeDB to generate necessary certificates.

    • apiGroup is the group name of the resource being referenced. The value for Issuer or ClusterIssuer is “cert-manager.io” (cert-manager v0.12.0 and later).
    • kind is the type of resource being referenced. KubeDB supports both Issuer and ClusterIssuer as values for this field.
    • name is the name of the resource (Issuer or ClusterIssuer) being referenced.
  • certificates (optional) are a list of certificates used to configure the server and/or client certificate. It has the following fields:

    • alias represents the identifier of the certificate. It has the following possible value:

      • server is used for server certificate identification.
      • client is used for client certificate identification.
      • metrics-exporter is used for metrics exporter certificate identification.
    • secretName (optional) specifies the k8s secret name that holds the certificates. This field is optional. If the user does not specify this field, the default secret name will be created in the following format: <database-name>-<cert-alias>-cert.

    • subject (optional) specifies an X.509 distinguished name. It has the following possible field,

      • organizations (optional) are the list of different organization names to be used on the Certificate.
      • organizationalUnits (optional) are the list of different organization unit name to be used on the Certificate.
      • countries (optional) are the list of country names to be used on the Certificate.
      • localities (optional) are the list of locality names to be used on the Certificate.
      • provinces (optional) are the list of province names to be used on the Certificate.
      • streetAddresses (optional) are the list of a street address to be used on the Certificate.
      • postalCodes (optional) are the list of postal code to be used on the Certificate.
      • serialNumber (optional) is a serial number to be used on the Certificate. You can found more details from Here
    • duration (optional) is the period during which the certificate is valid.

    • renewBefore (optional) is a specifiable time before expiration duration.

    • dnsNames (optional) is a list of subject alt names to be used in the Certificate.

    • ipAddresses (optional) is a list of IP addresses to be used in the Certificate.

    • uriSANs (optional) is a list of URI Subject Alternative Names to be set in the Certificate.

    • emailSANs (optional) is a list of email Subject Alternative Names to be set in the Certificate.

spec.configSecret

spec.configSecret is an optional field that allows users to provide custom configuration for MariaDB. This field accepts a VolumeSource.

spec.podTemplate

KubeDB allows providing a template for database pod through spec.podTemplate. KubeDB operator will pass the information provided in spec.podTemplate to the StatefulSet created for the MariaDB database.

KubeDB accepts the following fields to set in spec.podTemplate:

  • metadata:
    • annotations (pod’s annotation)
  • controller:
    • annotations (statefulset’s annotation)
  • spec:
    • args
    • env
    • resources
    • initContainers
    • imagePullSecrets
    • nodeSelector
    • affinity
    • serviceAccountName
    • schedulerName
    • tolerations
    • priorityClassName
    • priority
    • securityContext
    • livenessProbe
    • readinessProbe
    • lifecycle

Uses of some field of spec.podTemplate is described below,

spec.podTemplate.spec.args

spec.podTemplate.spec.args is an optional field. This can be used to provide additional arguments for database installation. To learn about available args of mysqld, visit here.

spec.podTemplate.spec.env

spec.podTemplate.spec.env is an optional field that specifies the environment variables to pass to the MariaDB docker image. To know about supported environment variables, please visit here.

Note that, KubeDB does not allow MYSQL_ROOT_PASSWORD, MYSQL_ALLOW_EMPTY_PASSWORD, MYSQL_RANDOM_ROOT_PASSWORD, and MYSQL_ONETIME_PASSWORD environment variables to set in spec.env. If you want to set the root password, please use spec.authSecret instead described earlier.

If you try to set any of the forbidden environment variables i.e. MYSQL_ROOT_PASSWORD in MariaDB crd, Kubed operator will reject the request with the following error,

Error from server (Forbidden): error when creating "./mariadb.yaml": admission webhook "mariadb.validators.kubedb.com" denied the request: environment variable MYSQL_ROOT_PASSWORD is forbidden to use in MariaDB spec

Also, note that KubeDB does not allow to update the environment variables as updating them does not have any effect once the database is created. If you try to update environment variables, KubeDB operator will reject the request with the following error,

Error from server (BadRequest): error when applying patch:
...
for: "./mariadb.yaml": admission webhook "mariadb.validators.kubedb.com" denied the request: precondition failed for:
...At least one of the following was changed:
    apiVersion
    kind
    name
    namespace
    spec.authSecret
    spec.init
    spec.storageType
    spec.storage
    spec.podTemplate.spec.nodeSelector
    spec.podTemplate.spec.env

spec.podTemplate.spec.imagePullSecrets

KubeDB provides the flexibility of deploying MariaDB database from a private Docker registry. spec.podTemplate.spec.imagePullSecrets is an optional field that points to secrets to be used for pulling docker image if you are using a private docker registry.

spec.podTemplate.spec.nodeSelector

spec.podTemplate.spec.nodeSelector is an optional field that specifies a map of key-value pairs. For the pod to be eligible to run on a node, the node must have each of the indicated key-value pairs as labels (it can have additional labels as well). To learn more, see here .

spec.podTemplate.spec.serviceAccountName

serviceAccountName is an optional field supported by KubeDB Operator (version 0.13.0 and higher) that can be used to specify a custom service account to fine-tune role-based access control.

If this field is left empty, the KubeDB operator will create a service account name matching MariaDB crd name. Role and RoleBinding that provide necessary access permissions will also be generated automatically for this service account.

If a service account name is given, but there’s no existing service account by that name, the KubeDB operator will create one, and Role and RoleBinding that provide necessary access permissions will also be generated for this service account.

If a service account name is given, and there’s an existing service account by that name, the KubeDB operator will use that existing service account. Since this service account is not managed by KubeDB, users are responsible for providing necessary access permissions manually.

spec.podTemplate.spec.resources

spec.podTemplate.spec.resources is an optional field. This can be used to request compute resources required by the database pods. To learn more, visit here.

spec.serviceTemplate

You can also provide a template for the services created by KubeDB operator for MariaDB database through spec.serviceTemplate. This will allow you to set the type and other properties of the services.

KubeDB allows following fields to set in spec.serviceTemplate:

  • metadata:
    • annotations
  • spec:
    • type
    • ports
    • clusterIP
    • externalIPs
    • loadBalancerIP
    • loadBalancerSourceRanges
    • externalTrafficPolicy
    • healthCheckNodePort
    • sessionAffinityConfig

See here to understand these fields in detail.

spec.halted

spec.halted is an optional field. Suppose you want to delete the MariaDB resources(StatefulSet, Service etc.) except MariaDB object, PVCs and Secret then you need to set spec.halted to true. If you set spec.halted to true then the terminationPolicy in MariaDB object will be set Halt by-default.

spec.terminationPolicy

terminationPolicy gives flexibility whether to nullify(reject) the delete operation of MariaDB crd or which resources KubeDB should keep or delete when you delete MariaDB crd. KubeDB provides the following four termination policies:

  • DoNotTerminate
  • Halt
  • Delete (Default)
  • WipeOut

When terminationPolicy is DoNotTerminate, KubeDB takes advantage of ValidationWebhook feature in Kubernetes 1.9.0 or later clusters to implement DoNotTerminate feature. If admission webhook is enabled, DoNotTerminate prevents users from deleting the database as long as the spec.terminationPolicy is set to DoNotTerminate.

Following table show what KubeDB does when you delete MariaDB crd for different termination policies,

BehaviorDoNotTerminateHaltDeleteWipeOut
1. Block Delete operation
2. Delete StatefulSet
3. Delete Services
4. Delete PVCs
5. Delete Secrets
6. Delete Snapshots

If you don’t specify spec.terminationPolicy KubeDB uses Delete termination policy by default.