pgBackRest CNPG-I plugin

Status: EXPERIMENTAL

Welcome to the codebase of the pgBackRest CNPG-I plugin for CloudNativePG.

Table of contents

• Features
• Prerequisites
• Installation
• Usage
  • WAL Archiving
  • Backup
  • Restore
  • Replica clusters

Features

This plugin enables continuous backup to object storage for a PostgreSQL cluster using the pgbackrest tool suite.

The features provided by this plugin are:

• Data Directory Backup
• Data Directory Restore
• WAL Archiving
• WAL Restoring
• Point-in-Time Recovery (PITR)
• Replica Clusters
• Client-side encryption of both backups and WAL archives

Warning

While all data necessary to use various restore modes in pgbackrest is properly stored in the object store, restore is currently tested only with full backup recovery to the latest backup. Reports on more advanced recovery attempts are welcome.

This plugin is currently only compatible with S3 object storage.

The following storage solutions have been tested and confirmed to work with this implementation:

• MinIO – An S3-compatible object storage solution.

Known missing features:

• support for other object storage solutions (GCS, Azure),
• backups from replicas,
• proper support for private certificate authorities.

Prerequisites

To use this plugin, ensure the following prerequisites are met:

• CloudNativePG version 1.25 or newer.
• cert-manager for enabling TLS communication between the plugin and the operator.

Installation

IMPORTANT NOTES:

1. The plugin must be installed in the same namespace where the operator is installed (typically cnpg-system).

2. Be aware that the operator's listening namespaces may differ from its installation namespace. Ensure you verify this distinction to avoid configuration issues.

Here’s an enhanced version of your instructions for verifying the prerequisites:

Step 1 - Verify the Prerequisites

If CloudNativePG is installed in the default cnpg-system namespace, verify its version using the following command:

kubectl get deployment -n cnpg-system cnpg-controller-manager \
  | grep ghcr.io/cloudnative-pg/cloudnative-pg

Example output:

image: ghcr.io/cloudnative-pg/cloudnative-pg:1.25.0

Ensure that the version displayed is 1.25 or newer.

Then, use the cmctl tool to confirm that cert-manager is correctly installed:

cmctl check api

Example output:

The cert-manager API is ready

Both checks are necessary to proceed with the installation.

Step 2 - Install the pgBackRest Plugin

Use kubectl to apply the manifest for the latest commit in the main branch:

kubectl apply -f \
  https://github.com/operasoftware/cnpg-plugin-pgbackrest/releases/download/v0.1.0/manifest.yaml

Example output:

customresourcedefinition.apiextensions.k8s.io/archives.pgbackrest.cnpg.opera.com created
serviceaccount/plugin-pgbackrest created
role.rbac.authorization.k8s.io/leader-election-role created
clusterrole.rbac.authorization.k8s.io/archive-editor-role created
clusterrole.rbac.authorization.k8s.io/archive-viewer-role created
clusterrole.rbac.authorization.k8s.io/metrics-auth-role created
clusterrole.rbac.authorization.k8s.io/metrics-reader created
clusterrole.rbac.authorization.k8s.io/plugin-pgbackrest created
rolebinding.rbac.authorization.k8s.io/leader-election-rolebinding created
clusterrolebinding.rbac.authorization.k8s.io/metrics-auth-rolebinding created
clusterrolebinding.rbac.authorization.k8s.io/plugin-pgbackrest-binding created
secret/plugin-pgbackrest--8tfddg42gf created
service/pgbackrest created
deployment.apps/pgbackrest created
certificate.cert-manager.io/pgbackrest-client created
certificate.cert-manager.io/pgbackrest-server created
issuer.cert-manager.io/selfsigned-issuer created

After these steps, the plugin will be successfully installed. Make sure it is ready to use by checking the deployment status as follows:

kubectl rollout status deployment \
  -n cnpg-system pgbackrest

Example output:

deployment "pgbackrest" successfully rolled out

This confirms that the plugin is deployed and operational.

Usage

Defining the Archive

An Archive object should be created for each pgbackrest storage configuration used in your PostgreSQL architecture. Below is an example configuration for using a single MinIO repository with encryption enabled:

apiVersion: pgbackrest.cnpg.opera.com/v1
kind: Archive
metadata:
  name: minio-store
spec:
  configuration:
    repositories:
      - destinationPath: /
        bucket: backups
        endpointURL: minio:9000
        disableVerifyTLS: true
        encryption: aes-256-cbc
        encryptionKey:
          name: minio
          key: ENCRYPTION_KEY
        s3Credentials:
          region: "dummy"
          accessKeyId:
            name: minio
            key: ACCESS_KEY_ID
          secretAccessKey:
            name: minio
            key: ACCESS_SECRET_KEY
    compression: zst
  instanceSidecarConfiguration:
    resources:
      requests:
        memory: "2Gi"
        cpu: "2"
      limits:
        memory: "2Gi"
        cpu: "2"

Important

Unlike Barman, pgBackRest requires object storage to be accessible over HTTPS. While it's possible to disable key verification and use self-signed keys, using HTTP endpoint is not possible.

Configuring WAL Archiving

Once the Archive is defined, you can configure a PostgreSQL cluster to archive WALs by referencing the configuration in the .spec.plugins section, as shown below:

apiVersion: postgresql.cnpg.io/v1
kind: Cluster
metadata:
  name: cluster-example
spec:
  instances: 3
  imagePullPolicy: Always
  plugins:
  - name: pgbackrest.cnpg.opera.com
    parameters:
      pgbackrestObjectName: minio-store
  storage:
    size: 1Gi

This configuration enables both WAL archiving and data directory backups.

Important

Archiving will only start working after at least one backup is created. That's due to the stanza creation process which currently is only executed on backups.

Performing a Base Backup

Once WAL archiving is enabled, the cluster is ready for backups. To create a backup, configure the backup.spec.pluginConfiguration section to specify this plugin:

apiVersion: postgresql.cnpg.io/v1
kind: Backup
metadata:
  name: backup-example
spec:
  method: plugin
  cluster:
    name: cluster-example
  target: primary
  pluginConfiguration:
    name: pgbackrest.cnpg.opera.com
    parameters:
      type: full

Important

Currently only backups from primary are supported. Trying to run backup from a replica will fail.

Tip

All keys defined in the parameters section are passed to the pgBackRest as flags. This feature makes it possible to configure some additional options, most notably backup type, for a single backup instead of globally.

Restoring a Cluster

To restore a cluster from an archive, create a new Cluster resource that references the archive containing the backup. Below is an example configuration:

apiVersion: postgresql.cnpg.io/v1
kind: Cluster
metadata:
  name: cluster-restore
spec:
  instances: 3
  imagePullPolicy: IfNotPresent
  bootstrap:
    recovery:
      source: source
  externalClusters:
  - name: source
    plugin:
      name: pgbackrest.cnpg.opera.com
      parameters:
        pgbackrestObjectName: minio-store
        stanza: cluster-example
  storage:
    size: 1Gi

Note

The above configuration does not enable WAL archiving for the restored cluster.

To enable WAL archiving for the restored cluster, include the .spec.plugins section alongside the externalClusters.plugin section, as shown below:

apiVersion: postgresql.cnpg.io/v1
kind: Cluster
metadata:
  name: cluster-restore
spec:
  instances: 3
  imagePullPolicy: IfNotPresent
  bootstrap:
    recovery:
      source: source
  plugins:
  - name: pgbackrest.cnpg.opera.com
    parameters:
      # Backup archive (push, read-write)
      pgbackrestObjectName: minio-store-bis
  externalClusters:
  - name: source
    plugin:
      name: pgbackrest.cnpg.opera.com
      parameters:
        # Recovery archive (pull, read-only)
        pgbackrestObjectName: minio-store
        stanza: cluster-example
  storage:
    size: 1Gi

The same archive may be used for both transaction log archiving and restoring a cluster, or you can configure separate stores for these purposes.

Configuring Replica Clusters

You can set up a distributed topology by combining the previously defined configurations with the .spec.replica section. Below is an example of how to define a replica cluster:

apiVersion: postgresql.cnpg.io/v1
kind: Cluster
metadata:
  name: cluster-dc-a
spec:
  instances: 3
  primaryUpdateStrategy: unsupervised

  storage:
    storageClass: csi-hostpath-sc
    size: 1Gi

  plugins:
  - name: pgbackrest.cnpg.opera.com
    parameters:
      pgbackrestObjectName: minio-store-a

  replica:
    self: cluster-dc-a
    primary: cluster-dc-a
    source: cluster-dc-b

  externalClusters:
  - name: cluster-dc-a
    plugin:
      name: pgbackrest.cnpg.opera.com
      parameters:
        pgbackrestObjectName: minio-store-a

  - name: cluster-dc-b
    plugin:
      name: pgbackrest.cnpg.opera.com
      parameters:
        pgbackrestObjectName: minio-store-b