Clone a database cluster in Kubernetes using a local backup

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This document describes how to clone a database cluster in Kubernetes using local backup of an AlloyDB Omni database cluster.

This document makes the following assumptions:

  • Your source and target database clusters are created on Google Kubernetes Engine, and the backup disks are Compute Engine persistent disks.
  • The Compute Engine persistent disks that are used as a backup disk in the database aren't used by other database clusters.

When you clone a database cluster, you follow these steps:

  1. Identify the backup disk information, such as the persistent volume name and Compute Engine persistent disk handler for the source database cluster backup disk. Make sure that you enabled the backup feature for the source database cluster, and that you have at least one successful backup. If these conditions aren't met, follow the instructions in Enable and schedule backups.
  2. Create a PersistentVolume resource to use an existing backup disk on the target database cluster to access the backup disk of the source database cluster.
  3. Create and apply the DBCluster resource manifest file on the target database cluster with the livenessProbe parameter disabled and backup disk information added.
  4. Use pgBackRest commands to verify source backups can be accessed.
  5. Use pgBackRest commands to restore the backup to the target database cluster.

Before you begin

  • Make sure you have access to the backup disk where your source database cluster backup is stored.
  • The source database cluster backup disk must be able to mount to the target database cluster. For more information, see Persistent Volumes. If the underlying storage backend doesn't support ReadOnlyMany (ROX) access, make sure that the backup disk isn't being used by any pods in the source cluster.
  • Since the source backup disk is mounted to the target database cluster, the pgBackRest.conf file is reused as-is.
  • Ensure you are logged in to the database as the postgres user.

Get source backup disk information

As part of the restore process, determine the backup disk Persistent Volume Claim (PVC) name for your source database cluster. PVCs are used within Kubernetes to manage persistent storage for applications.

The following sample commands help locate the underlying PV name and the Compute Engine persistent disk handler. In the example, all the backup disks are Compute Engine persistent disks, which can be accessed across Compute Engine VMs using the disk handler identifier.

  1. Connect to your target database cluster to find the PVC name:

     kubectl get pvc -n DB_CLUSTER_NAMESPACE | grep DB_CLUSTER_NAME | grep backuprepodisk

    Replace the following:

    • DB_CLUSTER_NAMESPACE: the Kubernetes namespace for this backup plan. It must match the namespace of the database cluster.

    • DB_CLUSTER_NAME: the name of this database cluster—for example, my-db-cluster.

    The following is the sample response.

        backuprepodisk-my-db-cluster-br-0   Bound
    pvc-36d8f05d-ef1a-4750-ac01-9bb330c15b3a   10Gi       RWO            standard-rwo   5d21h

  2. Use the backup disk PVC name from the previous step-—for example, backuprepodisk-my-db-cluster-br-0, to find the underlying PV name and Compute Engine persistent disk handler:

      kubectl get pvc/PVC_NAME -n DB_CLUSTER_NAMESPACE -o jsonpath={.spec.volumeName}

    Replace the following:

    • PVC_NAME: the PVC name of the backup disk from response in the previous step—for example backuprepodisk-my-db-cluster-br-0.

  3. Export the configurations based on the PV name as variables to be used in the subsequent sections:

      export BACKUP_DISK_SIZE=$(kubectl get pv/PV_NAME -o jsonpath="{.spec.capacity.storage}")
  export FS_TYPE=$(kubectl get pv/PV_NAME -o jsonpath="{.spec.csi.fsType}")
  export VOLUME_HANDLER=$(kubectl get pv/PV_NAME -o jsonpath="{.spec.csi.volumeHandle}")
  export STORAGE_CLASS=$(kubectl get pv/PV_NAME -o jsonpath="{.spec.storageClassName}")

    Replace the following:

    • PV_NAME: the PV name of the backup disk from response in the previous step. For example, "backupDiskVolume".

Create a persistent volume resource

Using the disk handler name, create a PersistentVolume resource.

  1. In the target Kubernetes cluster, create the PersistentVolume manifest file:

        apiVersion: v1
    kind: PersistentVolume
    metadata:
      name: PV_NAME
    spec:
      storageClassName: "${STORAGE_CLASS}"
      capacity:
        storage: "${BACKUP_DISK_SIZE}"
      accessModes:
        - ReadWriteOnce
      csi:
        driver: pd.csi.storage.gke.io
        volumeHandle: "${VOLUME_HANDLER}"
        fsType: "${FS_TYPE}"

    Replace the following:

    • PV_NAME: the name of the PersistentVolume resource that will be created.

  2. Apply the manifest file:

      kubectl apply -f PV_FILENAME

    Replace the following:

    • PV_FILENAME: the name of the PersistentVolume manifest file created in the previous step.

Create a target database cluster

Create a database cluster by temporarily disabling the livenessProbe parameter. After the restore finishes, reconfigure the livenessProbe parameter.

  1. Create the DBCluster manifest file:

      apiVersion: v1
  kind: Secret
  metadata:
    name: db-pw-DB_CLUSTER_NAME
  type: Opaque
  data:
    DB_CLUSTER_NAME: "ENCODED_PASSWORD"
  ---
  apiVersion: alloydbomni.dbadmin.goog/v1
  kind: DBCluster
  metadata:
    name: DB_CLUSTER_NAME
  spec:
    databaseVersion: "15.12.0"
    primarySpec:
      availabilityOptions:
        livenessProbe: "Disabled"
      adminUser:
        passwordRef:
          name: db-pw-DB_CLUSTER_NAME
      resources:
        cpu: CPU_COUNT
        memory: MEMORY_SIZE
        disks:
        - name: DataDisk
          size: DATA_DISK_SIZE
        - name: BackupDisk
          size: ${BACKUP_DISK_SIZE}
          storageClass: ${STORAGE_CLASS}
          volumeName: PV_NAME

    Replace the following:

    • DB_CLUSTER_NAME: the name of this database cluster—for example, my-db-cluster.

    • ENCODED_PASSWORD: the database login password for the default postgres user role, encoded as a base64 string—for example, Q2hhbmdlTWUxMjM= for ChangeMe123.

    • CPU_COUNT: the number of CPUs available to each database instance in this database cluster.

    • MEMORY_SIZE: the amount of memory per database instance of this database cluster. We recommend that you set this to 8 gigabytes per CPU. For example, if you set CPU_COUNT to 2, then we recommend that you set memory to 16Gi.

    • DATA_DISK_SIZE: the disk size per database instance, for example, 10Gi.

  2. Apply the manifest file:

      kubectl apply -f DBCLUSTER_FILENAME

    Replace the following:

    • DBCLUSTER_FILENAME: the name of the DBCluster manifest file created in the previous step.

Use the kubectl describe command to verify that the database cluster resource is in the READY status.

Verify source backups in target database cluster

Run pgBackRest commands to verify that the source database cluster backups are accessible on the target database cluster.

  1. In your target database cluster, find the database cluster pod details:

      kubectl get pod -l "alloydbomni.internal.dbadmin.goog/dbcluster=DB_CLUSTER_NAME, alloydbomni.internal.dbadmin.goog/task-type=database"

    The response includes the name of the cluster database pod.

  2. Log into the database pod:

      kubectl exec -ti DATABASE_POD_NAME  -- /bin/bash

    Replace the following:

    • DATABASE_POD_NAME : the name of the database cluster pod from the previous step.

  3. Stop the pod before updating the pgBackRest configuration file:

      supervisorctl.par stop postgres

  4. Update the pgBackRest configuration file:

      cp /backup/pgbackrest.conf /backup/pgbackrest.conf.bak
  rm /backup/pgbackrest.conf
  cat << EOF > /backup/pgbackrest.conf
  [db]
  pg1-path=/mnt/disks/pgsql/data
  pg1-socket-path=/tmp
  pg1-user=pgbackrest
  [global]
  log-path=/backup/logs
  log-level-file=info
  EOF

  5. Verify the source backups in the database cluster pod:

    pgbackrest --config-path=/backup --stanza=db --repo=1 info

    The following is a sample response:

      stanza: db
      status: ok
      cipher: none
      db (current)
          wal archive min/max (15): 000000010000000000000002/00000001000000000000000D
          full backup: 20240213-231400F
              timestamp start/stop: 2024-02-13 23:14:00+00 / 2024-02-13 23:17:14+00
              wal start/stop: 000000010000000000000003 / 000000010000000000000003
              database size: 38.7MB, database backup size: 38.7MB
              repo1: backup set size: 4.6MB, backup size: 4.6MB
          incr backup: 20240213-231400F_20240214-000001I
              timestamp start/stop: 2024-02-14 00:00:01+00 / 2024-02-14 00:00:05+00
              wal start/stop: 00000001000000000000000D / 00000001000000000000000D
              database size: 38.7MB, database backup size: 488.3KB
              repo1: backup set size: 4.6MB, backup size: 84.2KB
              backup reference list: 20240213-231400F

The timestamps in the response are used either to restore the full backup or to restore from a point in time from the recovery window.

Restore the backup in the target database cluster

After you identify the backup or a point in time you want to restore to, run pgBackRest commands in your target database cluster. For more information about these commands, see Restore Command.

The following are some sample pgBackRest restore commands:

  • Restore from a backup

    pgbackrest --config-path=/backup --stanza=db --repo=1 restore --set=20240213-231400F --type=immediate --target-action=promote --delta --link-all --log-level-console=info

  • Restore from a point in time

    pgbackrest --config-path=/backup --stanza=db --repo=1 restore --target="2024-01-22 11:27:22" --type=time --target-action=promote --delta --link-all --log-level-console=info

Restart the pod

After the restore command completes successfully, you can start the postgres process.

supervisorctl.par start postgres

After the postgres process starts, you can connect to the primary instance and run queries to verify that the data is restored from the backup. For more information, see Connect to AlloyDB Omni running on Kubernetes.

Configure the database cluster

After you clone a database cluster, configure your database cluster specifications. Make sure to turn on the livenessProbe parameter using the following command:

    kubectl patch dbcluster DBCLUSTER_FILENAME --type merge -p '{"spec":{"primarySpec":{"availabilityOptions":{"livenessProbe":"Enabled"}}}}'

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