I think it would be a worthwhile enhancement to distinguish between cancel_requested and canceled. The REST API could mark a task as cancel_requested, and once the worker successfully handles the request it can mark the task as canceled.

This would be handy for the CLI. The CLI currently exits immediately when polling tasks upon noticing that they are canceled. It could instead mark that the task has been requested to cancel, and wait to exit until it is actually exited. This would allow it to print the final progress report if there is one.

This would have aided in discovering the problem in #1082802[0], wherein it was found that cancellation was ignored.

[0] https://bugzilla.redhat.com/show_bug.cgi?id=1082802