can't connect to my sql while executing playbooks of openstack - centos7

Question

i already executed first two playbook successfully but while i am trying to execute setup_openstack.yml that is third playbook , it is showing this error:
PLAY [Prepare MQ/DB services] ************************************************************************************************************
TASK [Ensure Rabbitmq vhost] *************************************************************************************************************
Thursday 14 March 2019 11:20:34 +0530 (0:00:00.087) 0:00:00.087 ********
ok: [centos-infra_keystone_container-******* -> ip of container]
TASK [Ensure rabbitmq user] **************************************************************************************************************
Thursday 14 March 2019 11:20:36 +0530 (0:00:01.765) 0:00:01.852 ********
ok: [centos-infra keystone_container-*******-> ip of container]
TASK [Ensure Rabbitmq vhost] *************************************************************************************************************
Thursday 14 March 2019 11:20:38 +0530 (0:00:02.215) 0:00:04.067 ********
TASK [Ensure rabbitmq user] **************************************************************************************************************
Thursday 14 March 2019 11:20:38 +0530 (0:00:00.028) 0:00:04.095 ********
TASK [Create DB for service] *************************************************************************************************************
Thursday 14 March 2019 11:20:38 +0530 (0:00:00.031) 0:00:04.127 ********
fatal: [centos-infra_keystone_container-******-> ip of container]: FAILED! => {"changed": false, "failed": true, "msg": "unable to connect to database, check login_user and login_password are correct or /root/.my.cnf has the credentials. Exception message: (2003, 'Can\'t connect to MySQL server on \'ip of lb\' (113 \"No route to host\")')"}
NO MORE HOSTS LEFT *********************************************************