I'm following tutorials https://docs.openstack.org/nova/rocky/install/controller-install-ubuntu.html (here) to install nova, the problem is when I run the command su -s /bin/sh -c "nova-manage api_db sync" nova as root, I get this error:

2018-10-30 20:38:20.637 27542 WARNING oslo_db.sqlalchemy.engines [-] SQL connection failed. 10 attempts left.: DBConnectionError: (pymysql.err.OperationalError) (2003, "Can't connect to MySQL server on 'controller' ([Errno -2] No address found)") (Background on this error at: http://sqlalche.me/e/e3q8)

the output of ping controller:

PING controller (192.168.7.135) 56(84) bytes of data.
64 bytes from controller (192.168.7.135): icmp_seq=1 ttl=64 time=0.016 ms

The output of netstat -tunap| grep 3306:

tcp        0      0 192.168.7.135:3306      0.0.0.0:*               LISTEN      1658/mysqld

the output of select Host,User from user in mysql:

+-----------+-----------+
| Host      | User      |
+-----------+-----------+
| %         | glance    |
| %         | keystone  |
| %         | nova      |
| %         | placement |
| localhost | glance    |
| localhost | keystone  |
| localhost | nova      |
| localhost | placement |
| localhost | root      |
+-----------+-----------+

relevant configurations on /etc/nova/nova.conf:

[api_database]
connection = mysql+pymysql://nova:password@controller/nova_api
[database]
connection = mysql+pymysql://nova:password@controller/nova
[placement_database]
connection = mysql+pymysql://placement:password@controller/placement

I have already used same syntax to setup glance and that works fine.

I'm using ubuntu 18.04 and trying to install openstack rocky.How can I fix this?