Disallow or block Backup deletion if create Instance from Backup is in progress

[abh1sar]

problem

Create Instance from Backup feature added in #10140 .
Backup can be deleted after starting the Create Instance from Backup process which fails after some time saying backup doesn't exist.

versions

ACS 4.21.0

The steps to reproduce the bug

1. Start "Create Instance from Backup"
2. Delete the Backup used
3. Create Instance from Backup fails with error.
   ...

What to do about it?

Backup deletion should either be disallowed or queued until Create Instance from Backup is finished.

[DaanHoogland]

@abh1sar , is this already in place for during a restore?

[abh1sar]

@DaanHoogland Once a command reaches the agent, it is queued. In case of restore the restoreCommand is sent very quickly to the agent without much preprocessing.
In case of create Instance from backup, a new instance is first created, then a command is sent to the agent. So until the command is sent, backup can be deleted.

[DaanHoogland]

In case of restore the restoreCommand is sent very quickly to the agent without much preprocessing.

sorry to be nitpicking, but “very quickly” is not “instantly” ? just want to prevent possible issues.

[abh1sar]

The window is there for restore also but very small. The user has to give the delete command within seconds of the restore command. In case of a race, if backup deletion reaches the agent before restore, restore will eventually fail saying backup deleted.

I don't think we can control the command execution at this granularity (can we?). Similar issue can be with any command which is updating a resource and another command which is deleting the same resource are executed out of order. Then update will throw some error.

[DaanHoogland]

As long as the restore can fail gracefully (or the delete) I guess it is fine. Can the delete happen while the restore is busy? As long as the only destructive action is the user initiated delete, there is nothing to do further. (i.e. the delete must not influence any ongoing restore or install from backup)