In Ansible, how to combine variables from active r

Looking at "In Ansible, how to combine variables from separate files into one array?" one of the answers suggests using include_vars to get variables from several sources into one array, this is almost what I need but not quite.

I'm setting up cloudfront_logging which requires items in a awslogs_logs: array. I'd like to be able to add to this array for the roles that I have active, so Syslog in my common role but if I have a php role, I'd like it to include the php logs.

I think I could get include_vars to work for all roles, but I can't see how to get this to work for only the roles included in a build. So if I include the php role, include the php logs but not if it is not included.

I could, of course, include the array at the top level statically but that seems like it is architecturally a bit off as you'd expect a role to be able to deal with its' own logging.

Your roles can use a set_fact task to append information to a variable. For example, let's say you want roles to be able to register paths to log files in the logfiles fact; you could do something like this in each role:

- set_fact:
    logfiles: "{{ logfiles|default([]) + ['/var/log/something.log', '/var/log/anotherthing.log'] }}"

In other words, if roles/role1/tasks looks like this:

---
- set_fact:
    logfiles: "{{ logfiles|default([]) + ['/var/log/role1.log'] }}"

And roles/role2/tasks looks like this:

---
- set_fact:
    logfiles: "{{ logfiles|default([]) + ['/var/log/role2.log'] }}"

Then a playbook that looks like this:

---
- hosts: localhost
  gather_facts: false
  roles:
    - role1
    - role2

  tasks:
    - debug:
        var: logfiles

Will produce this output:


PLAY [localhost] ******************************************************************************

TASK [role1 : set_fact] ***********************************************************************
ok: [localhost]

TASK [role2 : set_fact] ***********************************************************************
ok: [localhost]

TASK [debug] **********************************************************************************
ok: [localhost] => {
    "logfiles": [
        "/var/log/role1.log", 
        "/var/log/role2.log"
    ]
}

PLAY RECAP ************************************************************************************
localhost                  : ok=3    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0