Labels and annotations

Resources in Kubernetes are organized in a flat structure, with no hierarchical information or relationship between them. However, such resources and objects can be linked together and put in relationship through labels and annotations.

Info

For more information, see the Kubernetes documentation on annotations and labels.

In brief:

An annotation is used to assign additional non-identifying information to resources with the goal of facilitating integration with external tools.
A label is used to group objects and query them through the Kubernetes native selector capability.

You can select one or more labels or annotations to use in your CloudNativePG deployments. Then you need to configure the operator so that when you define these labels or annotations in a cluster's metadata, they're inherited by all resources created by it (including pods).

Note

Label and annotation inheritance is the technique adopted by CloudNativePG instead of alternative approaches such as pod templates.

Predefined labels

CloudNativePG manages the following predefined labels:

cnpg.io/backupDate: The date of the backup in ISO 8601 format (YYYYMMDD). This label is available only on VolumeSnapshot resources.
cnpg.io/backupName: Backup identifier. This label is available only on VolumeSnapshot resources.
cnpg.io/backupMonth: The year/month when a backup was taken. This label is available only on VolumeSnapshot resources.
cnpg.io/backupTimeline: The timeline of the instance when a backup was taken. This label is available only on VolumeSnapshot resources.
cnpg.io/backupYear: The year a backup was taken. This label is available only on VolumeSnapshot resources.
cnpg.io/cluster: Name of the cluster.
cnpg.io/immediateBackup: Applied to a Backup resource if the backup is the first one created from a ScheduledBackup object having immediate set to true.
cnpg.io/instanceName: Name of the PostgreSQL instance (replaces the old and deprecated postgresql label).
cnpg.io/jobRole: Role of the job (that is, import, initdb, join, ...)
cnpg.io/onlineBackup: Whether the backup is online (hot) or taken when Postgres is down (cold). This label is available only on VolumeSnapshot resources.
cnpg.io/podRole: Distinguishes pods dedicated to pooler deployment from those used for database instances.
cnpg.io/poolerName: Name of the PgBouncer pooler.
cnpg.io/pvcRole: Purpose of the PVC, such as PG_DATA or PG_WAL.
cnpg.io/reload: Available on ConfigMap and Secret resources. When set to true, a change in the resource is automatically reloaded by the operator.
cnpg.io/userType: Specifies the type of PostgreSQL user associated with the Secret, either superuser (Postgres superuser access) or app (application-level user in CloudNativePG terminology), and is limited to the default users created by CloudNativePG (typically postgres and app).
role - deprecated: Whether the instance running in a pod is a primary or a replica. This label is deprecated, you should use cnpg.io/instanceRole instead.
cnpg.io/scheduled-backup: When available, name of the ScheduledBackup resource that created a given Backup object.
cnpg.io/instanceRole: Whether the instance running in a pod is a primary or a replica.

Predefined annotations

CloudNativePG manages the following predefined annotations:

container.apparmor.security.beta.kubernetes.io/*

Name of the AppArmor profile to apply to the named container. See AppArmor for details.

cnpg.io/backupEndTime

The time a backup ended. This annotation is available only on VolumeSnapshot resources.

cnpg.io/backupEndWAL

The WAL at the conclusion of a backup. This annotation is available only on VolumeSnapshot resources.

cnpg.io/backupStartTime

The time a backup started.

cnpg.io/backupStartWAL

The WAL at the start of a backup. This annotation is available only on VolumeSnapshot resources.

cnpg.io/coredumpFilter

Filter to control the coredump of Postgres processes, expressed with a bitmask. By default it's set to 0x31 to exclude shared memory segments from the dump. See PostgreSQL core dumps for more information.

cnpg.io/clusterManifest

Manifest of the Cluster owning this resource (such as a PVC). This label replaces the old, deprecated cnpg.io/hibernateClusterManifest label.

cnpg.io/fencedInstances

List of the instances that need to be fenced, expressed in JSON format. The whole cluster is fenced if the list contains the * element.

cnpg.io/forceLegacyBackup

Applied to a Cluster resource for testing purposes only, to simulate the behavior of barman-cloud-backup prior to version 3.4 (Jan 2023) when the --name option wasn't available.

cnpg.io/hash

The hash value of the resource.

cnpg.io/hibernation

Applied to a Cluster resource to control the declarative hibernation feature. Allowed values are on and off.

cnpg.io/managedSecrets

Pull secrets managed by the operator and automatically set in the ServiceAccount resources for each Postgres cluster.

cnpg.io/nodeSerial

On a pod resource, identifies the serial number of the instance within the Postgres cluster.

cnpg.io/operatorVersion

Version of the operator.

cnpg.io/pgControldata

Output of the pg_controldata command. This annotation replaces the old, deprecated cnpg.io/hibernatePgControlData annotation.

cnpg.io/podEnvHash

Deprecated, as the cnpg.io/podSpec annotation now also contains the pod environment.

cnpg.io/podPatch

Annotation can be applied on a Cluster resource.

When set to JSON-patch formatted patch, the patch will be applied on the instance Pods.

⚠️ WARNING: This feature may introduce discrepancies between the operator’s expectations and Kubernetes behavior. Use with caution and only as a last resort.

IMPORTANT: adding or changing this annotation won't trigger a rolling deployment of the generated Pods. The latter can be triggered manually by the user with kubectl cnpg restart.

cnpg.io/podSpec

Snapshot of the spec of the pod generated by the operator. This annotation replaces the old, deprecated cnpg.io/podEnvHash annotation.

cnpg.io/poolerSpecHash

Hash of the pooler resource.

cnpg.io/pvcStatus

Current status of the PVC: initializing, ready, or detached.

cnpg.io/reconcilePodSpec

Annotation can be applied to a Cluster or Pooler to prevent restarts.

When set to disabled on a Cluster, the operator prevents instances from restarting due to changes in the PodSpec. This includes changes to:

Topology or affinity
Scheduler
Volumes or containers

When set to disabled on a Pooler, the operator restricts any modifications to the deployment specification, except for changes to spec.instances.

cnpg.io/reconciliationLoop

When set to disabled on a Cluster, the operator prevents the reconciliation loop from running.

cnpg.io/reloadedAt

Contains the latest cluster reload time. reload is triggered by the user through a plugin.

cnpg.io/skipEmptyWalArchiveCheck

When set to true on a Cluster resource, the operator disables the check that ensures that the WAL archive is empty before writing data. Use at your own risk.

cnpg.io/skipWalArchiving

When set to enabled on a Cluster resource, the operator disables WAL archiving. This will set archive_mode to off and require a restart of all PostgreSQL instances. Use at your own risk.

cnpg.io/snapshotStartTime

The time a snapshot started.

cnpg.io/snapshotEndTime

The time a snapshot was marked as ready to use.

cnpg.io/validation

When set to disabled on a CloudNativePG-managed custom resource, the validation webhook allows all changes without restriction.

⚠️ WARNING: Disabling validation may permit unsafe or destructive operations. Use this setting with caution and at your own risk.

cnpg.io/volumeSnapshotDeadline

Applied to Backup and ScheduledBackup resources, allows you to control how long the operator should retry recoverable errors before considering the volume snapshot backup failed. In minutes, defaulting to 10.

kubectl.kubernetes.io/restartedAt

When available, the time of last requested restart of a Postgres cluster.

Prerequisites

By default, no label or annotation defined in the cluster's metadata is inherited by the associated resources. To enable label/annotation inheritance, follow the instructions provided in Operator configuration.

The following continues from that example and limits it to the following:

Annotations: categories
Labels: app, environment, and workload

Note

Feel free to select the names that most suit your context for both annotations and labels. You can also use wildcards in naming and adopt strategies like using mycompany/* for all labels or setting annotations starting with mycompany/ to be inherited.

Defining cluster's metadata

When defining the cluster, before any resource is deployed, you can set the metadata as follows:

apiVersion: postgresql.cnpg.io/v1
kind: Cluster
metadata:
  name: cluster-example
  annotations:
    categories: database
  labels:
    environment: production
    workload: database
    app: sso
spec:
     # ... <snip>

Once the cluster is deployed, you can verify, for example, that the labels were correctly set in the pods:

kubectl get pods --show-labels

Current limitations

Currently, CloudNativePG doesn't automatically propagate labels or annotations deletions. Therefore, when an annotation or label is removed from a cluster that was previously propagated to the underlying pods, the operator doesn't remove it on the associated resources.