Ansible variables

Hi, We have an OSA setup. During a service playbook, for example, say rabbitmq, which task or play is responsible for creating it's haproxy configuration ? I mean, where is the code in openstack ansible to say to gather the values from user_variables file for that particular service or gather it from conf.d ? For instance, for rabbitmq service, where is the code which says to get the rabbitmq management port for the backend to be 15671 ? I mean where is the source code for pulling it from user_variables file and also which variable from it ?