Ansible include roles that have been defined in hostvars - roles

Question

I am trying to do the following:
define appropriate host roles in hostvars
create a role to call ONLY the roles that relate to specific host and have been defined in a variable in hostvars
Is there a way to do this?
eg:
host_vars/hostname_one/mail.yml
roles_to_install:
- role_one
- role_two
- ...
run_all_roles.yml
---
- hosts: '{{ TARGET }}'
become: yes
...
roles:
- { role: "roles_to_install"}
Obviously this does not work.
Is there a way to make ansible-playbook -i <hosts_file> run_all_roles.yml -e "TARGET=hostname_one" to run?

Answer 1

This is not how you should be approaching your roles and inventories.
Instead, if you put your hosts in the inventory in appropriate groups you can use the hosts parameter of the playbook to drive what gets installed where.
For example I might have a typical web application that is running on NGINX with some application specific things (such as a Python environment), but is also fronted by some NGINX servers that may serve static content and there could also be a typical database.
My inventory might then look like this:
[frontend-web-nodes]
web-1.example.org
web-2.example.org
[application-nodes]
app-1.example.org
app-2.example.org
[database-nodes]
database.example.org
Now, I can create a playbook for my database role that goes and installs some database and configures and set hosts: database-nodes to make sure the play (and so the role(s) that it runs only targets the database.example.org box.
So something like this:
- name: database
hosts: database-nodes
roles:
- database
For my frontend and application web nodes I have a shared dependency on installing and configuring NGINX but my application servers also need some other things. So my front end web nodes can be configured with a simple play like this:
- name: frontend-web
hosts: frontend-web-nodes
roles:
- nginx
While for my application nodes I might either have something like this:
- name: application
hosts: application-nodes
roles:
- nginx
- application
Or I could just do this:
- name: application
hosts: application-nodes
roles:
- application
And in my roles/application/meta/main.yml define a dependency on the nginx role:
dependencies:
- role: nginx

Answer 2

As I commented the solution was easier than expected:
---
- hosts: '{{ TARGET }}'
become: yes
vars_files:
- ./vars/main.yml
roles:
- { role: "roleA", when: "'roleA' in roles_to_install" }
- { role: "roleB", when: "'roleB' in roles_to_install" }
...
Assuming that a correct roles_to_install var is defined inside host_vars/$fqdn/main.yml like so:
---
roles_to_install:
- roleA
- roleB
- ...
Thank you for you assistance guys

Answer 3

What about this:
playfile.yml:
- hosts: all
tasks:
- when: host_roles is defined
include_role:
name: "{{ role_item }}"
loop: "{{ host_roles }}"
loop_control:
loop_var: role_item
hostvars_file.yml:
host_roles:
- name: myrole1
myrole1_var1: "myrole1_value1"
myrole1_var2: "myrole1_value2"
- name: myrole2
myrole2_var1: "myrole2_value1"
myrole2_var2: "myrole2_value2"
but then your hostvar_roles would be run during task-execution, normally roles will be executed before tasks.
Alternativly why dont have a role for this:
roles/ansible.hostroles/tasks/main.yml:
---
# tasks file for ansible.hostroles
- when: host_roles is defined
include_role:
name: "{{ role_item }}"
loop: "{{ host_roles }}"
loop_control:
loop_var: role_item
playfile.yml:
- hosts: all
roles:
- ansible.hostroles