Allow to Configure File Exclusions and Inclusions

[tobru]

Summary

As user of K8up I want to specify which files get included or excluded in a backup So that unneeded files (like temp files) do not get backed up unnecessarily

Context

Some applications may write temp files that shouldn't get backed up. For these use cases it is necessary to define exclusions. Currently all files of a PVC are backed up, there is no way to specify which ones to include or exclude.

Out of Scope

Further links

• https://restic.readthedocs.io/en/stable/040_backup.html#including-and-excluding-files

Acceptance criteria

Given a list of files to exclude is configured When a backup runs Then only applicable files are backed up

Implementation Ideas

The easiest way to define these is either on the deployment or the PVC. Whichever is more sensible. These exclusion lists must be passed to the wrestic container.

The PVC is the appropriate place. Objects in K8s have a size limit of 1 MB (actually etcd, but the outcome is the same). Large exclusion sets will not be possible. We could also store the exclusion definition in a ConfigMap and reference this ConfigMap f.e. via an annotation in the PVC.

This means that the wrestic container needs additional parameter handling to add exclusions to the backup command. Also the operator needs some logic to find and filter these annotations.

Here's the documentation how restic handles excludes: https://restic.readthedocs.io/en/stable/040_backup.html#including-and-excluding-files