python - using uwsgi --emperor cannot create sock file

Question

Here is my nginx config

upstream app {
    server unix:///tmp/rate.sock;
}

and my uwsgi config

[uwsgi]
chdir           = /home/ubuntu/dev/rate/rate
module          = docrate.wsgi
home            = /home/ubuntu/dev/rate
master          = true
processes       = 10
socket          = /tmp/rate.sock
chmod-socket    = 666
vacuum = true

If I use uwsgi --ini rate_uwsgi.ini to start, it's fine. But if I use emperor, the sock file isn't created.

uwsgi --emperor /etc/uwsgi.d --uid www-data --gid www-data

I just wanna figure it out. And my uwsgi version is 1.9.11.