task meta field should be used for progress updates

[jkeifer]

The celery task meta field should be used to store progress updates, as well as to display the process completion time. It is likely that this functionality could be added to ebagis.transaction.atomic if it makes sense there.

Examples:
http://stackoverflow.com/questions/20548786/celery-how-to-retrieve-metadata-from-custom-states
http://docs.celeryproject.org/en/latest/userguide/tasks.html#custom-states