How to migrate a cluster

This is a guide on how to restore a backup that was made from a different cluster, (i.e. cluster migration via restore).

To perform a basic restore (from a local backup), see How to restore a local backup

Prerequisites

Restoring a backup from a previous cluster to a current cluster requires:

• A single unit Charmed PostgreSQL deployed and running
• Access to S3 storage
• Configured settings for S3 storage
• Backups from the previous cluster in your S3 storage
• Passwords from your previous cluster

Manage cluster passwords

When you restore a backup from an old cluster, it will restore the password from the previous cluster to your current cluster. Set the password of your current cluster to the previous cluster’s password:

juju run postgresql-k8s/leader set-password username=operator password=<previous cluster password>
juju run postgresql-k8s/leader set-password username=replication password=<previous cluster password> 
juju run postgresql-k8s/leader set-password username=rewind password=<previous cluster password>

List backups

To view the available backups to restore, use the command list-backups:

juju run postgresql-k8s/leader list-backups

This shows a list of the available backups (it is up to you to identify which backup-id corresponds to the previous-cluster):

backups: 
      |backup-id           | backup-type  | backup-status
      ----------------------------------------------------
      YYYY-MM-DDTHH:MM:SSZ  | physical     | finished
      

Restore backup

To restore your current cluster to the state of the previous cluster, run the restore command and pass the correct backup-id to the command:

juju run postgresql-k8s/leader restore backup-id=YYYY-MM-DDTHH:MM:SSZ 

Your restore will then be in progress. Once it is complete, your current cluster will represent the state of the previous cluster.