Comment 9 for bug 1658913

So, as far as I can see the socket was blocked because we had unsent message in it's queue and socket didn't close. This behavior in DEALER socket prevents process exiting when something is in the queue and it is controlled by zmq_linger option which by default is infinite waiting. I recommend to set up linger to some definite value with dynamic connections mode to avoid such blocking.

Please update nova.conf with the following:

[oslo_messaging_zmq]
zmq_linger = 60