Goal:

The current mechanism to cancel ongoing actions is based on a polling mechanism which checks the state in the database every second for every action and kills a thread where the action is being executed. This mechanism is highly inefficient in terms of performance, error prone, and managing properly the cancellation would require better support from actions.

That mechanism has been removed in  https://review.opendev.org/c/openstack/watcher/+/973274 upstream. This epic is intended to backport it to RHOSO18 as a proactive backport given its impact on performance and scalability.