CopyVolumeData enhancement to use Kopia

[mlavi]

In discussion with @michaelcourcy today, he noted that the Kanister CopyVolumeData function exists, but it appears to be Restic specific.

Can we use this function with Kopia and without a Kanister sidecar? Operators cannot implement the sidecar pattern.

[hairyhum]

What we can do about it is to deprecate the restic-specific functions and create new kopia-specific functions for backup compatibility.

[hairyhum]

Draft implementation using kopia repository server can be found here: #2143

[michaelcourcy]

Can we imagine a workflow that include snapshot + export, because the replacement you propose still require a sidecar correct ? We can imagine doing that in 5 steps

1. Take a snap
2. Create a PVC clone from the snap
3. Export the cloned (which is not an issue because the clone is an orphaned pvc)
4. Output the kopia identifier
5. Removed the cloned pvc

But that would make sense to create a function for doing the 5 altogether, it would take 3 arguments

arg	role	example
pvcName	The pvc we want to export	my-pvc
snapshotClass	The snapshot class to use to take the snapshot	ebs-snapclass
kopiaRepoPassword	The kopia repository password	myUn6ue$$ablepwd

And would output the kopia identifier

That would bring a lot to the blueprint author

• Waiting for the snapshot to be ready
• Waiting for the clone to be ready
• All the export : attach a datamover, handle password error, output progression in the logs, output meaningful error message, output kopia identifier
• Make sure the cloned PVC is properly removed

[hairyhum]

because the replacement you propose still require a sidecar correct

CopyVolumeData and CopyVolumeDataUsingKopiaServer create a new pod with PVC mounted to it, so that's not a sidecar. Or do you mean something else?

But that would make sense to create a function for doing the 5 altogether

That's an interesting question, a function which should do multiple stages sounds a lot like a blueprint. Composability of blueprints is a challenge of course.

What it looks to me is following steps:

1. CreateCSISnapshot (this one waits for completion)
2. RestoreCSISnapshot into temp PVC
3. CopyVolumeDataUsingKopiaServer (this one will save the PVC into kopia using temporary pod and return an identifier)
4. DeleteCSISnapshot
5. KubeOps delete temp PVC