Supported versions
CKAN version 2.4 or greater (including 2.7).
All versions support celery backend, but version 2.7 will use RQ. There are no changes required to use new backend - just start it using:
paster --plugin=ckan jobs worker -c /config.ini
instead of:
paster --plugin=ckan celeryd run -c /config.ini
Details at http://docs.ckan.org/en/latest/maintaining/background-tasks.html