Scheduled backup - clean up old backup data

[sokada1221]

Feature Request

Is your feature request related to a problem? Please describe:

PV for the scheduled backup job eventually becomes full. Currently manual intervention is needed to purge the old data.

Describe the feature you'd like:

Implement a retention policy feature where scheduled backup automatically purges data that is more than the configured backup data retention number. e.g. If 3 is configured, at most 3 backup data is kept on disk. Any additional successful backup will replace the oldest backup data.

Describe alternatives you've considered:

https://github.com/pingcap/tidb-operator/issues/841

Teachability, Documentation, Adoption, Migration Strategy:

For example, a new configuration like the following can be added:

# Determines how many backup data to keep on disk. Defaults to 3.
retention-count = 10

[aylei]

Thanks!

Considering the disk space issue, would a number based retention policy be better? e.g. keep the latest 3 backups.

And, IMHO, if there's a upstream store configured, the backup data can be deleted immediately when uploaded. Then, the retention policy and deleting backup after upload (consider the PV as a temporary store) can be solved in 2 separate issues.

[sokada1221]

Good catch! Yes, number based retention would be better.

And OK, I'll open another issue for the following:

If that takes too much implementation effort, we can workaround with immediate delete upon successful upload to CEPH/S3/GCP.

[sokada1221]

@aylei Logged another ticket for the short-term solution, and updated this ticket to focus on the retention part.

[gregwebs]

We are creating a backup controller now that I think will be able to address these concerns.

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