Backup and Restore Workloads using Stash

This guide will show you how Stash backs up and restores volumes of various workload types (Deployment, StatefulSet, DaemonSet etc.).

Before You Begin

• You should be familiar with the following Stash concepts:
  • BackupConfiguration
  • BackupSession
  • RestoreSession
  • Repository

How Backup Process Works

The following diagram shows how Stash takes backup of the volumes of a workload. Open the image in a new tab to see the enlarged version.

  

The backup process consists of the following steps:

1. At first, a user creates a Secret. This secret holds the credentials to access the backend where the backed up data will be stored.

2. Then, she creates a Repository crd which represents the original repository in the backend.

3. Then, she creates a BackupConfiguration crd which specifies the targeted workload and desired file paths to backup. It also specifies the Repository object that holds the backend information where the backed up data will be stored.

4. Stash operator watches for BackupConfiguration objects.

5. When it finds a BackupConfiguration object, it finds the targeted workload and injects a sidecar named stash.

6. It also creates a CronJob to trigger backups periodically.

7. TheCronJob triggers backup on each scheduled slot by creating a BackupSession crd.

8. The stash sidecar inside the workload watches for BackupSession crd.

9. When it finds a BackupSession crd, it initiates backup of the targeted file paths.

10. Once the backup process is completed, the sidecar sends Prometheus metrics to the Pushgateway running inside the stash-operator pod. It also updates respective BackupSession and Repository status to reflect the backup process.

How Restore Process Works

The following diagram shows how Stash restores backed up data inside a workload. Open the image in a new tab to see the enlarged version.

  

The restore process consists of the following steps:

1. At first, the user creates a workload where the data will be restored.

2. Then, she creates a RestoreSession crd that specifies the targeted workload where the backed up data will be restored. It also specifies the respective Repository that holds the respective backend information.

3. Stash operator watches for RestoreSession crds.

4. When it finds a RestoreSession crd, it injects an init-container named stash-init to the workload and restart it.

5. The init-container restores the desired data from the backend on start-up.

6. Finally, when the restore process is completed it sends Prometheus metrics to the pushgateway running inside the stash operator. It also update the RestoreSession status to reflect the restore process.

Note: If your workload restarts with the stash-init init-container for any reason, the init-container will skip running restore process if there is no pending RestoreSession for this workload.

Next Steps

1. See a step by step guide to backup/restore volumes of a Deployment here.
2. See a step by step guide to backup/restore volumes of a StatefulSet here.
3. See a step by step guide to backup/restore a Daemonset’s volumes here.