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Percona Operators Documentation

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Labels and annotations

Labels and annotations are rather similar but differ in purpose.

Labels are used by Kubernetes to identify and select objects. They enable filtering and grouping, allowing users to apply selectors for operations like deployments or scaling.

Annotations are assigning additional non-identifying information that doesn’t affect how Kubernetes processes resources. They store descriptive information like deployment history, monitoring configurations or external integrations.

The following diagram illustrates this difference:

graph TD
    A[Custom Resource] --> B[Operator]
    B --> C[Kubernetes resources]
    C --> D[Labels]
    C --> E[Annotations]
    D --> F[Selection]
    D --> G[Grouping]
    E --> H[External tools]
    E --> I[Documentation]

Both Labels and Annotations are assigned to the following objects managed by Percona Operator for MySQL:

  • Custom Resource Definitions
  • Custom Resources
  • Deployments
  • Services
  • StatefulSets
  • PVCs
  • Pods
  • ConfigMaps and Secrets

When to use labels and annotations

Use Labels when:

  • The information is used for object selection
  • The data is used for grouping or filtering
  • The information is used by Kubernetes controllers
  • The data is used for operational purposes

Use Annotations when:

  • The information is for external tools
  • The information is used for debugging
  • The data is used for monitoring configuration

Labels and annotations used by Percona Operator for MySQL

Labels

Name Objects Description Example values
app.kubernetes.io/name Services, StatefulSets, Deployments, etc. Specifies the name of the application percona-xtradb-cluster
app.kubernetes.io/instance Pods, Services, StatefulSets, Deployments Identifies a specific instance of the application cluster1
app.kubernetes.io/managed-by Services, StatefulSets Indicates the controller managing the object percona-xtradb-cluster-operator
app.kubernetes.io/component Pods, Services, StatefulSets Specifies the component within the application pxc, proxysql, haproxy
app.kubernetes.io/part-of Services, StatefulSets Indicates the higher-level application the object belongs to percona-xtradb-cluster
app.kubernetes.io/version CustomResourceDefinition Specifies the version of the Percona XtraDB Cluster Operator. mysql.percona.com/1.18.0
percona.com/cluster Custom Resource Identifies the MySQL cluster instance cluster1
percona.com/backup-type Custom Resource Specifies the type of backup being performed (e.g. cron for scheduled backups) cron, xtrabackup
percona.com/backup-name Custom Resource Specifies the name of backup being performed backup1
percona.com/backup-job-name Job Specifies the name of the backup job being performed
percona.com/backup-ancestor Custom Resource Specifies the name of the backup that was used as a base for the current backup cluster1-backup-2025-05-23
percona.com/restore-svc-name Pods, PVC Identifies resources associated with a specific restore operation
percona.com/restore-job-name Pods, Jobs Specifies the name of a restore job being performed
rack Pods, Services, Deployments, StatefulSets Identifies topology or rack awareness, often for scheduling or affinity rack-22

Annotations

Name Associated resources Description Example values
iam.amazonaws.com/role Custom Resource AWS IAM role for service account iam.amazonaws.com/role: role-arn
testName Backup jobs, Pods Used for test identification in scheduled backups testName: scheduled-backup
percona.com/last-applied-tls Services Stores the hash of the last applied TLS configuration for the service
percona.com/last-applied-secret Secrets Stores the hash of the last applied user Secret configuration
percona.com/configuration-hash Services Used to track and validate configuration changes in the MySQL cluster components percona.com/last-applied-secret: "hashvalue"
percona.com/last-config-hash Services Stores the hash of the most recent configuration
percona.com/passwords-updated Secrets Indicates when passwords were last updated in the Secret
percona.com/issue-vault-token Custom Resource Signals the Operator to pause a cluster startup until a Vault token has been issued. Once the annotation is removed, the Operator restarts the cluster to apply the new Vault configuration and activate encryption
percona.com/issue-vault-token: "true"
service.beta.kubernetes.io/aws-load-balancer-backend-protocol Services Specifies the protocol for AWS load balancers http, http-test
service.beta.kubernetes.io/aws-load-balancer-backend Services Specifies the backend type for AWS load balancers test-type

Setting labels and annotations in the Custom Resource

You can define both Labels and Annotations as key-value pairs in the metadata section of a YAML manifest for a specific resource. For example, specifying labels and annotations in the deploy/cr.yaml Custom Resource looks as follows:

apiVersion: pxc.percona.com/v1
kind: PerconaXtraDBCluster
metadata:
  name: cluster1
  annotations:
    percona.com/issue-vault-token: "true"
  labels:
    ...

Note

The percona.com/issue-vault-token: "true" annotation is a special case. If you set this annotation and use HashiCorp Vault (for example, for data at rest encryption), the Operator will pause the cluster startup and repeatedly log wait for token issuing until you remove the annotation. This lets you automate Vault setup before the cluster starts.

Querying labels and annotations

To check which labels are attached to a specific object, use the additional --show-labels option of the kubectl get command.

For example, to see the Operator version associated with a Custom Resource Definition, use the following command:

$ kubectl get crd perconaxtradbclusters.pxc.percona.com --show-labels
Sample output 
NAME                                    CREATED AT             LABELS
perconaxtradbclusters.pxc.percona.com   2025-07-29T09:02:34Z   app.kubernetes.io/component=crd,app.kubernetes.io/name=percona-xtradb-cluster,app.kubernetes.io/part-of=percona-xtradb-cluster-operator,app.kubernetes.io/version=v1.18.0

To check annotations associated with an object, use the following command:

$ kubectl get <resource> <resource-name> -o jsonpath='{.metadata.annotations}'

For example:

$ kubectl get pod cluster1-pxc-0 -o jsonpath='{.metadata.annotations}'

Specifying labels and annotations ignored by the Operator

Sometimes various Kubernetes flavors can add their own annotations to the objects managed by the Operator.

The Operator keeps track of all changes to its objects and can remove annotations that it didn’t create.

If there are no annotations or labels in the Custom Resource, the Operator does nothing if a new label or an annotation is added to the object.

If there is an annotation or a label specified in the Custom Resource, the Operator starts to manage annotations and labels. In this case it removes unknown annotations and labels.

A cloud provider can add own labels and annotations. Or you may have custom automation tools that add own labels or annotations and you need to keep them. To do this, you can specify which annotations and labels the Operator should ignore by listing them in the spec.ignoreAnnotations or spec.ignoreLabels keys of the deploy/cr.yaml, as follows:

spec:
  ignoreAnnotations:
    - some.custom.cloud.annotation/smth
  ignoreLabels:
    - some.custom.cloud.label/smth
...

The Operator will ignore any Service annotation or label, key of which starts with the mentioned above examples. For example, the following annotations and labels will be ignored after applying the above cr.yaml fragment:

annotations:
  some.custom.cloud.annotation/smth: somethinghere
labels:
  some.custom.cloud.label/smth: somethinghere
Last update: 2025-08-14