Comment 0 for bug 1715141

The executor parameter controls how incoming messages will be received and dispatched. By default, the most simple executor is used - the blocking executor. It handles only one message at once. It's
recommended to use threading or eventlet. And it has been marked for removal in Rocky.

 http://git.openstack.org/cgit/openstack/oslo.messaging/tree/oslo_messaging/server.py#n337