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MySQL
What is MySQL
MySQL
is a Kubernetes Custom Resource Definitions
(CRD). It provides declarative configuration for MySQL in a Kubernetes native way. You only need to describe the desired database configuration in a MySQL object, and the KubeDB operator will create Kubernetes objects in the desired state for you.
MySQL Spec
As with all other Kubernetes objects, a MySQL needs apiVersion
, kind
, and metadata
fields. It also needs a .spec
section. Below is an example MySQL object.
apiVersion: kubedb.com/v1
kind: MySQL
metadata:
name: m1
namespace: demo
spec:
version: "8.0.35"
topology:
mode: GroupReplication
authSecret:
name: m1-auth
storageType: "Durable"
storage:
storageClassName: "standard"
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 1Gi
init:
script:
configMap:
name: my-init-script
monitor:
agent: prometheus.io/operator
prometheus:
serviceMonitor:
labels:
app: kubedb
interval: 10s
requireSSL: true
tls:
issuerRef:
apiGroup: cert-manager.io
kind: Issuer
name: mysql-issuer
certificates:
- alias: server
subject:
organizations:
- kubedb:server
dnsNames:
- localhost
ipAddresses:
- "127.0.0.1"
configSecret:
name: my-custom-config
podTemplate:
metadata:
annotations:
passMe: ToDatabasePod
controller:
annotations:
passMe: ToPetSet
spec:
serviceAccountName: my-service-account
schedulerName: my-scheduler
nodeSelector:
disktype: ssd
imagePullSecrets:
- name: myregistrykey
containers:
- name: mysql
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
deletionPolicy: Halt
spec.version
spec.version
is a required field specifying the name of the MySQLVersion crd where the docker images are specified. Currently, when you install KubeDB, it creates the following MySQLVersion
resources,
8.0.35
,8.0.35
,8.0.17
,8.0.3-v4
8.0.31-innodb
5.7.44
,5.7.35-v1
,5.7.25-v2
spec.topology
spec.topology
is an optional field that provides a way to configure HA, fault-tolerant MySQL cluster. This field enables you to specify the clustering mode. Currently, we support only MySQL Group Replication. KubeDB uses PodDisruptionBudget
to ensure that majority of the group replicas are available during voluntary disruptions so that quorum is maintained and no data loss has occurred.
You can specify the following fields in spec.topology
field,
mode
specifies the clustering mode for MySQL. For now, the supported value is"GroupReplication"
for MySQL Group Replication. This field is required if you want to deploy MySQL cluster.group
is an optional field to configure a group replication. It contains the following fields:name
is an optional field to specify the name for the group. It must be a version 4 UUID if specified.
spec.authSecret
spec.authSecret
is an optional field that points to a Secret used to hold credentials for mysql
root user. If not set, the KubeDB operator creates a new Secret {mysql-object-name}-auth
for storing the password for mysql
root user for each MySQL object. If you want to use an existing secret please specify that when creating the MySQL object using spec.authSecret.name
.
This secret contains a user
key and a password
key which contains the username
and password
respectively for mysql
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 m1-auth -n demo \
--from-literal=user=root \
--from-literal=password=6q8u_2jMOW-OOZXk
secret "m1-auth" created
apiVersion: v1
data:
password: NnE4dV8yak1PVy1PT1pYaw==
user: cm9vdA==
kind: Secret
metadata:
name: m1-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 MySQL database 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 PetSet 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 MySQL database. MySQL databases can be initialized in one of two ways:
- Initialize from Script
Initialize via Script
To initialize a MySQL database using a script (shell script, sql script, etc.), set the spec.init.script
section when creating a MySQL 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:
- VolumeSource: Where your script is loaded from.
Below is an example showing how a script from a configMap can be used to initialize a MySQL database.
apiVersion: kubedb.com/v1
kind: MySQL
metadata:
name: m1
namespace: demo
spec:
version: 8.0.35
init:
script:
configMap:
name: mysql-init-script
In the above example, KubeDB operator will launch a Job to execute all js script of mysql-init-script
in alphabetical order once PetSet pods are running. For more details tutorial on how to initialize from script, please visit here.
spec.monitor
MySQL managed by KubeDB can be monitored with builtin-Prometheus and Prometheus operator out-of-the-box. To learn more,
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 MySQL.
The following fields are configurable in the spec.tls
section:
issuerRef
is a reference to theIssuer
orClusterIssuer
CR of cert-manager that will be used byKubeDB
to generate necessary certificates.apiGroup
is the group name of the resource being referenced. The value forIssuer
orClusterIssuer
is “cert-manager.io” (cert-manager v0.12.0 and later).kind
is the type of resource being referenced. KubeDB supports bothIssuer
andClusterIssuer
as values for this field.name
is the name of the resource (Issuer
orClusterIssuer
) 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 anX.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 MySQL. 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 PetSet created for the MySQL database.
KubeDB accepts the following fields to set in spec.podTemplate:
- metadata:
- annotations (pod’s annotation)
- controller:
- annotations (petset’s annotation)
- spec:
- containers
- volumes
- podPlacementPolicy
- initContainers
- imagePullSecrets
- nodeSelector
- serviceAccountName
- schedulerName
- tolerations
- priorityClassName
- priority
- securityContext
You can check out the full list here.
Uses of some field of spec.podTemplate
is described below,
spec.podTemplate.spec.tolerations
The spec.podTemplate.spec.tolerations
is an optional field. This can be used to specify the pod’s tolerations.
spec.podTemplate.spec.volumes
The spec.podTemplate.spec.volumes
is an optional field. This can be used to provide the list of volumes that can be mounted by containers belonging to the pod.
spec.podTemplate.spec.podPlacementPolicy
spec.podTemplate.spec.podPlacementPolicy
is an optional field. This can be used to provide the reference of the podPlacementPolicy. This will be used by our Petset controller to place the db pods throughout the region, zone & nodes according to the policy. It utilizes kubernetes affinity & podTopologySpreadContraints feature to do so.
spec.podTemplate.spec.containers
The spec.podTemplate.spec.containers
can be used to provide the list containers and their configurations for to the database pod. some of the fields are described below,
spec.podTemplate.spec.containers[].name
The spec.podTemplate.spec.containers[].name
field used to specify the name of the container specified as a DNS_LABEL. Each container in a pod must have a unique name (DNS_LABEL). Cannot be updated.
spec.podTemplate.spec.containers[].args
spec.podTemplate.spec.containers[].args
is an optional field. This can be used to provide additional arguments to database installation.
spec.podTemplate.spec.containers[].env
spec.podTemplate.spec.containers[].env
is an optional field that specifies the environment variables to pass to the MySQL 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 MySQL crd, Kubed operator will reject the request with the following error,
Error from server (Forbidden): error when creating "./mysql.yaml": admission webhook "mysql.validators.kubedb.com" denied the request: environment variable MYSQL_ROOT_PASSWORD is forbidden to use in MySQL 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: "./mysql.yaml": admission webhook "mysql.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.containers[].resources
spec.podTemplate.spec.containers[].resources
is an optional field. This can be used to request compute resources required by containers of the database pods. To learn more, visit here.
spec.podTemplate.spec.imagePullSecrets
KubeDB
provides the flexibility of deploying MySQL 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. To learn how to deploy MySQL 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 MySQL 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. Follow the guide here to grant necessary permissions in this scenario.
spec.serviceTemplate
You can also provide a template for the services created by KubeDB operator for MySQL 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. This field will be used to halt the kubeDB operator. When you set spec.halted
to true
, the KubeDB operator doesn’t perform any operation on MySQL
object.
Suppose you want to delete the MySQL
resources(PetSet
, Service
etc.) except MySQL
object, PVCs
and Secret
then you need to set spec.halted
to true
. If you set spec.halted
to true
then the deletionPolicy
in MySQL
object will be set Halt
by-default.
spec.deletionPolicy
deletionPolicy
gives flexibility whether to nullify
(reject) the delete operation of MySQL
crd or which resources KubeDB should keep or delete when you delete MySQL
crd. KubeDB provides the following four termination policies:
- DoNotTerminate
- Halt
- Delete (
Default
) - WipeOut
When deletionPolicy
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.deletionPolicy
is set to DoNotTerminate
.
Following table show what KubeDB does when you delete MySQL crd for different termination policies,
Behavior | DoNotTerminate | Halt | Delete | WipeOut |
---|---|---|---|---|
1. Block Delete operation | ✓ | ✗ | ✗ | ✗ |
2. Delete PetSet | ✗ | ✓ | ✓ | ✓ |
3. Delete Services | ✗ | ✓ | ✓ | ✓ |
4. Delete PVCs | ✗ | ✗ | ✓ | ✓ |
5. Delete Secrets | ✗ | ✗ | ✗ | ✓ |
6. Delete Snapshots | ✗ | ✗ | ✗ | ✓ |
If you don’t specify spec.deletionPolicy
KubeDB uses Delete
termination policy by default.
Next Steps
- Learn how to use KubeDB to run a MySQL database here.
- Want to hack on KubeDB? Check our contribution guidelines.