Clone a database cluster in a single server using a local backup

This page shows you how to clone a database cluster in a single server using local backup.

The steps on this page assume that the source Kubernetes database cluster is created on Google Kubernetes Engine, and the backup disks are Compute Engine persistent disks. It also assumes that the target AlloyDB Omni single server is installed on a Compute Engine virtual machine (VM).

If you use other environments, refer to the respective documentation to replicate these steps in your environment.

The following workflow explains the cloning steps:

  1. Identify the backup disk information, such as the persistent volume name and Compute Engine persistent disk handler, for source database cluster backup disk.
  2. Mount the backup disk of the source database cluster to the target server.
  3. Use pgBackRest commands to verify source backups can be accessed.
  4. 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.
  • A single server target AlloyDB Omni database cluster is created. For more information about installing AlloyDB Omni on Kubernetes, see Install AlloyDB Omni.
  • 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 determine the underlying PV name and the Compute Engine persistent disk handler using the backup disk PVC name.

  1. Connect to your GKE cluster where you have created the AlloyDB Omni source database cluster:

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

    Replace the following:

    • DB_CLUSTER_NAMESPACE: the Kubernetes namespace for this backup. 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.

      backupdisk-al-fe8c-dbcluster-sample-0   Bound
  pvc-36d8f05d-ef1a-4750-ac01-9bb330c15b3a   10Gi       RWO            standard-rwo   5d21h
  ```

  2. Use the backup disk name from the previous step-—for example, backupdisk-al-fe8c-dbcluster-sample-0, to find the underlying PV name:

      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 backupdisk-al-fe8c-dbcluster-sample-0.

  3. Find the underlying Compute Engine persistent disk handler:

      kubectl get pv/$PV_NAME -o json | jq -r .spec.csi.volumeHandle

    Replace the following:

    • PV_NAME: the PV name of the backup disk from response in the previous step.

    The following is the sample response:

      projects/my-project/zones/us-central1-a/disks/pvc-89f91fba-6cd2-4bfa-84ed-cb5969b446c3

  4. Export the backup disk name as a variable used in the next sections:

      export BACKUP_DISK=pvc-89f91fba-6cd2-4bfa-84ed-cb5969b446c3

Mount the backup disk to the target server

Assuming that the target server is an AlloyDB Omni server installed on a Compute Engine virtual machine, mount the backup disk to the server.

  1. Run the gcloud compute instances attach-disk command to mount the disk:

      gcloud compute instances attach-disk GCE_INSTANCE_NAME \
  --disk ${BACKUP_DISK} \
  --zone=$GCE_ZONE

    Replace the following:

    • GCE_INSTANCE_NAME: the name of the instance where your target server is installed in Compute Engine virtual machine.

    • GCE_ZONE: the zone where your Compute Engine virtual machine instance exists.

  2. Mount the backup disk to the target server:

       lsblk
   mkdir -p /mnt/disks/backupdisk
   mount -o discard,defaults /dev/sdb /mnt/disks/backupdisk

  3. Add a custom bind mount to the AlloyDB Omni dataplane.conf file in the /var/alloydb/config directory:

      PG_BIND_MOUNTS=/mnt/disks/backupdisk:/mnt/disks/backups:rshared

For more information about bind mounts in docker, see Bind mounts.

  1. Restart the target server:

      alloydb database-server stop
  alloydb database-server start

Update the pgBackRest configuration file

Update the existing pgBackRest file in the backup disk directory with the new repository path.

  1. In the target server, go to the /mnt/disks/backupdisk directory:

      cd /mnt/disks/backupdisk

  2. Update the pg1-path path to a temporary directory in the pgbackrest.conf file to avoid overwriting the existing data. The data-restored directory is created automatically as part of the restore process:

      sudo sed -i 's|.*pg1-path.*|pg1-path=/mnt/disks/pgsql/data-restored|' pgbackrest.conf

  3. Update the repo1-path path to a temporary directory in the pgbackrest.conf file:

      sudo sed -i 's|.*repo1-path.*|repo1-path=/mnt/disks/backups/repo|' conf.d/repo1-local-backupplan.conf

Verify source backups in target database cluster

Sign in to the target server, and run pgBackRest commands to verify that the source database cluster backups are accessible on the target server:

    sudo docker exec pg-service pgbackrest --config-path=/mnt/disks/backups --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 server

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

The following are some sample pgBackRest restore commands:

  • Restore from a backup

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

Copy data to target server

After the restore command completes successfully, you can copy the data from the data-restored temporary directory to the current AlloyDB data directory.

  1. In the target server, stop the database service:

    alloydb database-server stop

  2. Rename the current data directory to another name as a best practice:

      mv ~/alloydb-data/data  ~/alloydb-data/data-old

  3. Rename the data-restored temporary directory to current data directory:

      mv ~/alloydb-data/data-restored ~/alloydb-data/data

  4. Update pg1-path value in the postgresql.auto.conf file to load the restored data:

        vim ~/alloydb-data/data/postgresql.auto.conf
    # Verify postgresql.auto.conf.
    # Do not edit this file manually!
    # It will be overwritten by the ALTER SYSTEM command.
    # Recovery settings generated by pgBackRest restore on 2024-03-13 20:47:11
    restore_command = 'pgbackrest --config-path=/mnt/disks/pgsql --pg1-path=/mnt/disks/pgsql/data --repo=1 --stanza=db archive-get %f "%p"'
    recovery_target = 'immediate'
    recovery_target_action = 'promote'
    recovery_target_timeline = 'current'

  5. In the target server, start the database service:

    alloydb database-server start

After the database service 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 on a single server.

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