Dry-run mode

[vrutkovs]

Changes in the operator may be destructive, the operator should have a mode where diffs are printed, but not applied

[AndrewChubatiuk]

looks like a feature that requires UI

[vrutkovs]

There are several options here:

• print diffs to the log
  Can we ensure the diff would be pretty-printed? See also Improve diff support #1821
• Store it in the object annotation

Perhaps we should research whether other operators are doing something similar

[AndrewChubatiuk]

Suppose its better to make a cli tool that returns a pretty diff between already deployed resources and desired instead of making logging more noisy (want treat this and diff improve as completely different tasks). Additionally it allows to check diff before operator upgrade. It can be an operator subcommand

operator diff vmagent test -n default

[vrutkovs]

My idea was:

• before upgrade, users turn on dry-run mode
• operator upgrade
• operator prints diffs into the log (Improve diff support #1821), possibly printing whether pod rollouts will occur explicitly
• administrator waits until the maintenance period starts, switches the dry run mode off
• rollouts are performed, cluster state is reconciled, maintenance ends

[AndrewChubatiuk]

With a separate cli tool there's no need to pause operator and it possible to generate a terraform like fancy diff with list of resources that are expected to me created, removed, updated or recreated

[AndrewChubatiuk]

released in 0.68.4