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Snapshot

What is Snapshot

A Snapshot is a Kubernetes CustomResourceDefinition(CRD) which represents the state of a backup run for one or more components of an application. For every BackupSession, it creates Snapshot CRs. If a BackupSession involves multiple repositories, a Snapshot is created for each repository.

KubeStash operator is responsible for creating Snapshot CR. Snapshot CR is not supposed to be created/edited by the end user.

Snapshot CRD Specification

Like any official Kubernetes resource, a Snapshot has TypeMeta, ObjectMeta, Spec and Status sections.

A sample Snapshot object is shown below,

apiVersion: storage.kubestash.com/v1alpha1
kind: Snapshot
metadata:
  labels:
    kubestash.com/app-ref-kind: StatefulSet
    kubestash.com/app-ref-name: sample-sts
    kubestash.com/app-ref-namespace: demo
    kubestash.com/repo-name: gcs-demo-repo
  name: gcs-demo-repo-sample-backup-sts-demo-session-1702543201
  namespace: demo
spec:
  appRef:
    apiGroup: apps
    kind: StatefulSet
    name: sample-sts
    namespace: demo
  backupSession: sample-backup-sts-demo-session-1702543201
  deletionPolicy: Delete
  repository: gcs-demo-repo
  session: demo-session
  snapshotID: 01HHKQQ59XN4979HMDFNCANA9V
  type: FullBackup
  version: v1
status:
  components:
    dump-pod-0:
      driver: Restic
      duration: 10.595356615s
      integrity: true
      path: repository/v1/demo-session/dump-pod-0
      phase: Succeeded
      resticStats:
        - hostPath: /source/data
          id: cb64ffb35297f15cd93cfedc280b7e10267aaef283626fa564a32f69468a6bc2
          size: 10.240 MiB
          uploaded: 10.242 MiB
      size: 10.242 MiB
    dump-pod-1:
      driver: Restic
      duration: 8.789930136s
      integrity: true
      path: repository/v1/demo-session/dump-pod-1
      phase: Succeeded
      resticStats:
        - hostPath: /source/data
          id: 489d5a7614daa663df0c69a53a36d353936b6c8be61b8472694eeabcedbde16f
          size: 1.978 MiB
          uploaded: 1.979 MiB
      size: 1.979 MiB
    dump-pod-2:
      driver: Restic
      duration: 6.261958475s
      integrity: true
      path: repository/v1/demo-session/dump-pod-2
      phase: Succeeded
      resticStats:
        - hostPath: /source/data
          id: 17a7bc582a1f39fa54beb96f37f6f806f86d39ca575777391fcf69ddfc1bbab7
          size: 13 B
          uploaded: 1.056 KiB
      size: 809 B
  conditions:
    - lastTransitionTime: "2023-12-14T08:40:01Z"
      message: Recent snapshot list updated successfully
      reason: SuccessfullyUpdatedRecentSnapshotList
      status: "True"
      type: RecentSnapshotListUpdated
    - lastTransitionTime: "2023-12-18T08:50:57Z"
      message: Metadata uploaded to backend successfully
      reason: SuccessfullyUploadedSnapshotMetadata
      status: "True"
      type: SnapshotMetadataUploaded
  integrity: true
  phase: Succeeded
  size: 12.222 MiB
  snapshotTime: "2023-12-14T08:40:10Z"
  totalComponents: 3

Here, we are going to describe the various sections of a Snapshot object.

Snapshot Metadata

metadata.name

metadata.name specifies the name of the Snapshot object. It follows the following pattern, <Repository name>-<BackupSession name>.

metadata.labels

A Snapshot object holds repository and target application kind, name and namespace as a label in metadata.labels section. This helps a user to query the Snapshots of a particular repository and/or a particular target application.

Snapshot Spec

spec.snapshotID

spec.snapshotID represents a Universally Unique Lexicographically Sortable Identifier(ULID) for the Snapshot. For more details about ULID, please see here

spec.type

spec.type specifies whether this snapshot represents a FullBackup or IncrementalBackup.

spec.repository

spec.repository specifies the name of the Repository where this Snapshot is being stored.

spec.session

spec.session specifies the name of the session which is responsible for this Snapshot.

spec.backupSession

spec.backupSession represents the name of the respective BackupSession which is responsible for this Snapshot.

spec.version

spec.version denotes the respective data organization structure inside the Repository.

spec.appRef

spec.appRef specifies the reference of the application that has been backed up in this Snapshot.

spec.deletionPolicy

spec.deletionPolicy specifies what to do when you delete a Snapshot CR. The valid values are:

• Delete This will delete just the Snapshot CR from the cluster but keep the backed up data in the remote backend. This is the default behavior.
• WipeOut This will delete the Snapshot CR as well as the backed up data from the backend.

spec.paused

spec.paused specifies whether the Snapshot is paused or not. If the Snapshot is paused, KubeStash will not process any further event for the Snapshot.

Snapshot Status

Snapshot object has the following fields in .status section:

status.phase

status.phase represents the backup state of this Snapshot.

status.snapshotTime

status.snapshotTime represents the original creation timestamp for this Snapshot.

status.lastUpdateTime

status.lastUpdateTime specifies the timestamp when this Snapshot was last updated.

status.size

status.size represents the size of the Snapshot.

status.integrity

status.integrity represents whether the Snapshot data has been corrupted or not.

status.conditions

status.conditions represents list of conditions regarding this Snapshot. KubeStash sets the following conditions for a Snapshot:

status.totalComponents

status.totalComponents represents the number of total components for this Snapshot.

status.components

status.components represents the backup information of the individual components of this Snapshot. Each component consists of the following fields:

• path : specifies the path inside the Repository where the backed up data for this component has been stored. This path is relative to Repository path.
• phase : represents the backup phase of the component.
• size : represents the size of the restic repository for this component.
• duration : specifies the total time taken to complete the backup process for this component.
• integrity : represents the result of the restic repository integrity check for this component.
• error : specifies the reason in case of backup failure for the component.
• driver : specifies the name of the tool that has been used to upload the underlying backed up data.
• resticStats : specifies the Restic driver specific information. Each resticStat consists of the following fields:
  • id : represents the restic snapshot id.
  • uploaded : specifies the amount of data that has been uploaded in the restic snapshot.
  • hostPath : represents the backup path for which restic snapshot is taken.
  • size : represents the restic snapshot size.
• volumeSnapshotterStats : specifies the VolumeSnapshotter driver specific information. Each volumeSnapshotterStat consists of the following fields:
  • pvcName : represents the backup PVC name for which volumeSnapshot was created.
  • hostPath : represents the mount path of PVC for which volumeSnapshot was created.
  • volumeSnapshotName : represents the name of created volumeSnapshot.
  • volumeSnapshotTime : indicates the timestamp at which the volumeSnapshot was created.
• walSegments : specifies a list of wall segment for individual component. Each walSegment consists of start time and end time fields.

Next Steps

• Learn how to configure BackupConfiguration to backup workloads data from here.
• Learn how to configure BackupConfiguration to backup stand-alone PVC from here.