Description of problem:

Sync / publish tasks cancelled in the UI are not actually getting cancelled when the user performs a cancel. The worker proccess continues to execute the task.  Pulp's REST API says the cancellation is successful and the task status is marked as CANCELLED. However, the details of the task continue to get updated as a sync or publish continues to run. Users can experience delays in other tasks starting because the workers are busy executing cancelled tasks.

Version-Release number of selected component (if applicable):


Any release of Satellite 6 that uses python2-celery 4.0.2.


How reproducible:

Every time

Steps to Reproduce:

1) Start a sync of a single repository.
2) Look at output of 'top' and make note of CPU usage of a single celery process that is performing the sync. 
3) Go to the task details and click the cancel button. 
4) Look at the output of 'top' and observe that the same celery process is still using just as much CPU. 

Actual results:

The celery process continues executing the task.

Expected results:

Celery process stops executing the task. 

Additional info:

The actual problem is in the kombu package. There is already a patch for it upstream. https://github.com/celery/kombu/pull/1029/