How to get hostvars in dynamically matched playbook?

[Nicolas Neubauer]

Hi,

I have a dynamic inventory of ec2 hosts that have tags to declare how those should be provisioned. My use-case is as follows:

- 1 EC2 host has a tag "tomcat" and "use"

- 2 EC2 hosts have a tag "mysql"

  one of them has a tag "use"

  on of them has a tag "dont-use"

I'd like to provision only the "use" hosts. The challenge is that the tomcat host needs a variable with the ip address of the mysql host. I currently have a playbook that matches on all hosts in the "use" group. Then I apply the roles using when: 'mysql' in group_names, 'tomcat' respectively.

roles:

- {

   role: 'my_tomcat_role',

   mysql_ip: "WHAT TO PUT HERE?",

   when: "'tomcat' in group_names",

   sudo: yes

  }

I have played around with various techniques. Eg. try to dynamically group_by in the pre tasks to create temp groups of all hosts that have been matched by the playbook but that does not work, because group_by seems to implicitly only run_once and thus can not use the group_names:

  - group_by: key=current_{{ item }}

    with_items: "{{ group_names }}"

The above does not work.

I can not register variables because those will only be available per host, so that does not work either because I don't know the hostname of the mysql-tagged instance.

Any ideas? Maybe this is a feature request to allow to select hostvars/hosts by the same pattern syntax that is available in the playbook hosts: directive.

Thanks,

Nicolas