It is possible to pause and later resume a background task, as well as completely abort it. This is useful in case there are other tasks/activities that are of higher priority.
Command:
weka cluster task pause / resume / abort <task-id>
This command is used to pause/resume/abort the running of a specific task.
Note: Up to 16 background tasks can run in parallel. A paused (or aborting) task still consumes one of these spots.