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BackupConfiguration

What is BackupConfiguration

A BackupConfiguration is a Kubernetes CustomResourceDefinition(CRD) which specifies the backup target, parameters(schedule, retention policy etc.) and a Repository object that holds snapshot storage information in a Kubernetes native way.

You have to create a BackupConfiguration object for each backup target. A backup target can be a workload, database or a PV/PVC.

BackupConfiguration CRD Specification

Like any official Kubernetes resource, a BackupConfiguration has TypeMeta, ObjectMeta and Spec sections. However, unlike other Kubernetes resources, it does not have a Status section.

A sample BackupConfiguration object to backup the volumes of a Deployment is shown below:

apiVersion: stash.appscode.com/v1beta1
kind: BackupConfiguration
metadata:
  name: demo-backup
  namespace: demo
spec:
  driver: Restic
  repository:
    name: local-repo
    namespace: demo
  # task:
  #   name: workload-backup # task field is not required for workload data backup but it is necessary for database backup.
  schedule: "* * * * *" # backup at every minutes
  paused: false
  backupHistoryLimit: 3
  timeOut: 2h
  target:
    alias: app-data
    ref:
      apiVersion: apps/v1
      kind: Deployment
      name: stash-demo
    paths:
    - /source/data
    exclude:
    - /source/data/not-important.txt
    - /source/data/*.html
    - /source/data/tmp/*
    volumeMounts:
    - name: source-data
      mountPath: /source/data
  hooks:
    preBackup:
      exec:
        command:
          - /bin/sh
          - -c
          - echo "Sample PreBackup hook demo"
      containerName: my-app-container
    postBackup:
      executionPolicy: Always
      exec:
        command:
          - /bin/sh
          - -c
          - echo "Sample PostBackup hook demo"
      containerName: my-app-container
  runtimeSettings:
    container:
      resources:
        requests:
          memory: 256M
        limits:
          memory: 256M
      securityContext:
        runAsUser: 2000
        runAsGroup: 2000
      nice:
        adjustment: 5
      ionice:
        class: 2
        classData: 4
    pod:
      imagePullSecrets:
      - name:  my-private-registry-secret
      serviceAccountName: my-backup-svc
  tempDir:
    medium: "Memory"
    sizeLimit: "2Gi"
    disableCaching: false
  retryConfig:
    maxRetry: 3
    delay: 10m
  retentionPolicy:
    name: 'keep-last-5'
    keepLast: 5
    prune: true

Here, we are going to describe the various sections of BackupConfiguration crd.

BackupConfiguration Spec

A BackupConfiguration object has the following fields in the spec section.

spec.driver

spec.driver indicates the mechanism used to backup a target. Currently, Stash supports Restic and VolumeSnapshotter as drivers. The default value of this field is Restic.

spec.target

spec.target field indicates the target for backup runs. This field consists of the following sub-fields:

• spec.target.alias : The alias is used as an identifer of the backed up data in the backend. This is particularly useful for BackupBatch where multiple targets are backed up into a single repository.

• spec.target.ref : spec.target.ref refers to the target of backup. You have to specify apiVersion, kind and name of the target. Stash will use this information to inject a sidecar to the target or to create a backup job for it.

• spec.target.paths : spec.target.paths specifies list of file paths to backup.

• spec.target.exclude : Specifies a list of pattern for the files that should be ignored during backup. Stash will not backup the files that matches these patterns.

• spec.target.volumeMounts : spec.target.volumeMounts are the list of volumes and their mountPaths that contain the target file paths. Stash will mount these volumes inside a sidecar container or a backup job.

• spec.target.snapshotClassName: spec.target.snapshotClassName indicates the VolumeSnapshotClass to use for volume snasphotting. Use this field only if spec.driver is set to VolumeSnapshotter.

spec.repository

spec.repository specifies the name and namespace of the Repository CR that holds the necessary backend information where the backed up data will be stored.

• spec.repository.name specifies the name of the Repository CR.
• spec.repository.namespace specifies the namespace of the Repository. If you don’t provide this field, Stash will look for the Repository CR in the same namespace as the BackupConfiguration.

spec.schedule

spec.schedule is a cron expression that specifies the schedule of backup. Stash creates a Kubernetes CronJob with this schedule.

spec.backupHistoryLimit

spec.backupHistoryLimit specifies the number of BackupSession and its associate resources (Job, PVC etc.) to keep for debugging purposes. The default value of this field is 1. Stash will cleanup the old BackupSession and it’s associate resources after each backup session according to backupHistoryLimit. Stash will always keep the last completed BackupSession when backuphistorylimit>0. It will keep the last completed BackupSession even if it exceeds the history limit. This will help to keep the backup history when a backup gets skipped due to another running backup.

spec.timeOut

spec.timeOut specifies the maximum amount of time to wait for the backup to complete. If the backup doesn’t complete within this time limit, Stash will mark the respective BackupSession as Failed. You can specify the timeout in the following format:

• Seconds 30s
• Minutes 10m
• Hours 1h
• Combination of seconds, minutes, and hours 10m30s, 1h30m etc.

Stash does not support providing days (d) in the timeOut field. Use the equivalent hours instead.

spec.task

spec.task specifies the name and parameters of the Task crd to use to backup the target.

• spec.task.name: spec.task.name indicates the name of the Task to use for this backup process.
• spec.task.params: spec.task.params is an array of custom parameters to use to configure the task.

spec.task section is not required for backing up workload data (i.e. Deployment, DaemonSet, StatefulSet etc.). However, it is necessary for backing up databases and stand-alone PVCs.

spec.paused

spec.paused can be used as enable/disable switch for backup. If it is set true, Stash will not take any backup of the target specified by this BackupConfiguration.

spec.hooks

spec.hooks allows performing some actions before and after the backup process. You can send HTTP requests to a remote server via httpGet or httpPost hooks. You can check whether a TCP socket is open using tcpSocket hook. You can also execute some commands into your application pod using exec hook.

• spec.hooks.preBackup: spec.hooks.preBackup hooks are executed before the backup process.
• spec.hooks.postBackup: spec.hooks.postBackup hooks are executed after the backup process. Unlike the preBackup hook, postBackup hook has an extra field named executionPolicy which let you execute hook based on the backup status. Currently, it support the following values:
  • Always: The hook will be executed after the backup process no matter the backup has failed or succeeded. This is the default behavior.
  • OnSuccess: The hook will be executed after the backup process only if the backup has succeeded.
  • OnFailure: The hook will be executed after the backup process only if the backup has failed.

For more details on how hooks work in Stash and how to configure different types of hook, please visit here.

spec.runtimeSettings

spec.runtimeSettings allows to configure runtime environment for the backup sidecar or job. You can specify runtime settings at both pod level and container level.

• spec.runtimeSettings.container

  spec.runtimeSettings.container is used to configure the backup sidecar/job at container level. You can configure the following container level parameters:

• spec.runtimeSettings.pod

  spec.runtimeSettings.pod is used to configure backup job in pod level. You can configure the following pod level parameters,

spec.tempDir

Stash mounts an emptyDir for holding temporary files. It is also used for caching for faster backup performance. You can configure the emptyDir using spec.tempDir section. You can also disable caching using this field. The following fields are configurable in spec.tempDir section:

• spec.tempDir.medium : Specifies the type of storage medium should back this directory.
• spec.tempDir.sizeLimit : Maximum limit of storage for this volume.
• spec.tempDir.disableCaching : Disable caching while backup. This may negatively impact backup performance. This is set to false by default.

spec.interimVolumeTemplate

For some targets (i.e. some databases), Stash can’t directly pipe the dumped data to the uploading process. In this case, it has to store the dumped data temporarily before uploading to the backend. spec.interimVolumeTemplate specifies a PVC template for holding those data temporarily. Stash will create a PVC according to the template and use it to store the data temporarily. This PVC will be deleted according to the spec.backupHistoryLimit.

Note that the usage of this field is different than spec.tempDir which is used for caching purpose. Stash has introduced this field because the emptyDir volume that is used for spec.tempDir does not play nice with large databases( i.e. 100Gi database). Also, it provides debugging capability as Stash keeps it until it hits the limit specified in spec.backupHistoryLimit.

spec.retryConfig

spec.retryConfig is an optional field the let users to specify a retry logic for failed backup. It has the following fields:

• spec.retryConfig.maxRetry specifies the maximum number of times Stash should retry a failed backup.

• spec.retryConfig.delay specifies the amount of time to wait before retrying a failed backup. You can specify the delay in the following format:

  • Seconds 30s
  • Minutes 10m
  • Hours 1h
  • Combination of seconds, minutes, and hours 10m30s, 1h30m etc.

  Stash does not support providing days (d) in the delay field. Use the equivalent hours instead.

spec.retentionPolicy

spec.retentionPolicy specifies the policy to follow for cleaning old snapshots. Following options are available to configure retention policy:

BackupConfiguration Status

A BackupConfiguration object has the following fields in the status section.

• observedGeneration : The most recent generation observed by the BackupConfiguration controller.

• conditions : The spec.conditions shows current backup setup condition for this BackupConfiguration. The following conditions are set by the Stash operator:

Next Steps

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