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PerconaXtraDB

What is PerconaXtraDB

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

PerconaXtraDB Spec

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

apiVersion: kubedb.com/v1alpha2
kind: PerconaXtraDB
metadata:
  name: demo-px
  namespace: demo
spec:
  version: "5.7"
  replicas: 3
  authSecret:
    name: demo-px-auth
  storageType: "Durable"
  storage:
    storageClassName: "standard"
    accessModes:
    - ReadWriteOnce
    resources:
      requests:
        storage: 1Gi
  monitor:
    agent: prometheus.io/operator
    prometheus:
      serviceMonitor:
        labels:
          app: kubedb
        interval: 10s
  podTemplate:
    metadata:
      annotations:
        passMe: ToDatabasePod
    controller:
      annotations:
        passMe: ToStatefulSet
    spec:
      serviceAccountName: px-service-account
      schedulerName: px-scheduler
      nodeSelector:
        disktype: ssd
      imagePullSecrets:
      - name: myregistrykey
      args:
      - --character-set-server=utf8mb4
      env:
      - name: MYSQL_DATABASE
        value: myDB
      resources:
        requests:
          memory: "64Mi"
          cpu: "250m"
        limits:
          memory: "128Mi"
          cpu: "500m"
  serviceTemplates:
  - alias: primary
    metadata:
      annotations:
        passMe: ToService
    spec:
      type: NodePort
      ports:
      - name:  http
        port:  9200
  terminationPolicy: Halt

.spec.version

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

  • 5.7
  • 5.7-cluster

.spec.replicas

.spec.replicas specifies the number of instances to deploy for PerconaXtraDB. If set to 1, KubeDB will deploy a standalone Percona server. If set to value larger than 1, deploy PerconaXtraDB cluster with specified number of masters.

To learn more about how to setup a Percona XtraDB cluster using KubeDB, please visit here.

.spec.authSecret

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

This secret contains a username key and a password key which contains the username and password respectively for mysql root user. Here, the value of username 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 demo-px-auth -n demo \
    --from-literal=username=root \
    --from-literal=password=6q8u_2jMOW-OOZXk
secret/demo-px-auth created
apiVersion: v1
data:
  password: NnE4dV8yak1PVy1PT1pYaw==
  username: cm9vdA==
kind: Secret
metadata:
  ...
  name: demo-px-auth
  namespace: demo
  ...
type: Opaque

.spec.storageType

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

.spec.storage

Since 0.9.0-rc.0, 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 PerconaXtraDB. PerconaXtraDB can be initialized in one of two ways:

  1. Initialize from Script
  2. Initialize from Snapshot

Initialize via Script

To initialize a PerconaXtraDB database (with replica 1) using a script (shell script, sql script etc.), set the .spec.init.script section when creating a PerconaXtraDB object. It will execute files alphabetically with extensions .sh , .sql and .sql.gz that are found in the repository. The scripts inside child folders will be skipped. script must have following information:

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

apiVersion: kubedb.com/v1alpha2
kind: PerconaXtraDB
metadata:
  name: init-demo-px
  namespace: demo
spec:
  version: "5.7"
  init:
    script:
      configMap:
        name: my-init-script

In the above example, KubeDB operator will launch a Job to execute all js script of my-init-script in alphabetical order once StatefulSet Pods are running. For more details tutorial on how to initialize from script, please visit here.

Initialize from Stash Backup

If you have a backup of PerconaXtraDB cluster using Stash, you can initialize from it. To initialize, set the .spec.init.stashRestoreSession section when creating a PerconaXtraDB object. In this case, StashRestoreSession must have following information:

  • name: Name of the RestoreSession object
apiVersion: kubedb.com/v1alpha2
kind: PerconaXtraDB
metadata:
  name: px-new
spec:
  version: 5.7
  ...
  init:
    stashRestoreSession:
      name: "snapshot-xyz"

In the above example, PerconaXtraDB cluster will be initialized from Snapshot snapshot-xyz. Here, Stash operator will launch necessary Jobs to initialize once StatefulSet Pods are running.

When initializing from Snapshot, root user credentials must have to match with the previous one. For example, let’s say, Snapshot snapshot-xyz is for PerconaXtraDB px-old. In this case, new PerconaXtraDB px-new should use the same credentials for root user of px-old. Otherwise, the restoration process will fail.

For more details tutorial on how to initialize from snapshot, please visit here.

.spec.monitor

PerconaXtraDB managed by KubeDB can be monitored with builtin-Prometheus and Prometheus operator out-of-the-box. To learn more,

.spec.configSecret

.spec.configSecret is an optional field that allows users to provide custom configuration for PerconaXtraDB. This field accepts a VolumeSource. So you can use any kubernetes supported volume source such as configMap, secret, azureDisk etc. To learn more about how to use a custom configuration file see here.

.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 PerconaXtraDB.

KubeDB accept 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

Usage 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 to 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 PerconaXtraDB 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 PerconaXtraDB object, KubeDB operator will reject the request with following error,

Error from server (Forbidden): error when creating "./percona-xtradb.yaml": admission webhook "perconaxtradb.validators.kubedb.com" denied the request: environment variable MYSQL_ROOT_PASSWORD is forbidden to use in PerconaXtraDB 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 following error,

Error from server (BadRequest): error when applying patch:
...
for: "./percona-xtradb.yaml": admission webhook "perconaxtradb.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.imagePullSecrets

KubeDB provides the flexibility of deploying PerconaXtraDB 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. To learn how to deploy PerconaXtraDB from a private registry, please visit here.

.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 PerconaXtraDB object 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. Follow the guide here to grant necessary permissions in this scenario.

.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 PerconaXtraDB 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.terminationPolicy

terminationPolicy gives flexibility whether to nullify(reject) the delete operation of PerconaXtraDB object or which resources KubeDB should keep or delete when you delete PerconaXtraDB object. KubeDB provides 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 PerconaXtraDB object for different termination policies,

BehaviorDoNotTerminateHaltDeleteWipeOut
1. Block Delete operation
2. Create Dormant Database
3. Delete StatefulSet
4. Delete Services
5. Delete PVCs
6. Delete Secrets

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

Next Steps