It turns out that eventlet.green.threading.Event() doesn't behave very efficiently in this context for whatever reason.
Use eventlet.event.Event() instead. It was not used before due to lack of timeout and clear, but that is overcome by
disposing of it rather than reusing and using with eventlet.Timeout() to add timeout to wait that doesn't have built in timeout.
If wanting to run as non-root, mkdir -p /var/run/confluent /var/log/confluent /etc/confluent
and chown those to be owned by confluent user. That is probably path for deb and rpm packaging.