Ansible, how to set a global fact using roles?

Question

I'm trying to use Ansible to deploy a small k3s cluster with just two server nodes at the moment. Deploying the first server node, which I refer to as "master" is easy to set up with Ansible. However, setting up the second server node, which I refer to as "node" is giving me a challenge because I need to pull the value of the node-token from the master and use it to call the k3s install command on the "node" vm.

I'm using Ansible roles, and this is what my playbook looks like:

- hosts: all

  roles:
    - { role: k3sInstall , when: 'server_type is defined'}
    - { role: k3sUnInstall , when: 'server_type is defined'}

This is my main.yml file from the k3sInstall role directory:

- name: Install k3s Server
  import_tasks: k3s_install_server.yml
  tags:
    - k3s_install

This is my k3s_install_server.yml:

---
- name: Install k3s Cluster
  block:
    - name: Install k3s Master Server
      become: yes
      shell: "{{ k3s_master_install_cmd }}"
      when: server_role == "master"

    - name: Get Node-Token file from master server.
      become: yes
      shell: cat {{ node_token_filepath }}
      when: server_role == "master"
      register: nodetoken
    
    - name: Print Node-Token
      when: server_role == "master"
      debug:
        msg: "{{ nodetoken.stdout }}"
        # msg: "{{ k3s_node_install_cmd }}"

    - name: Set Node-Token fact
      when: server_role == "master"
      set_fact:
        nodeToken: "{{ nodetoken.stdout }}"

    - name: Print Node-Token fact
      when: server_role == "node" or server_role == "master"
      debug:
        msg: "{{ nodeToken }}"
    # - name: Install k3s Node Server
    #   become: yes
    #   shell: "{{ k3s_node_install_cmd }}{{ nodeToken }}"
    #   when: server_role == "node"

I've commented out the Install k3s Node Servertask because I'm not able to properly reference the nodeToken variable that I'm setting when server_role == master.

This is the output of the debug:

TASK [k3sInstall : Print Node-Token fact] ***************************************************************************************************************************************************************************************************************************************************************************
ok: [server1] => {
    "msg": "K10cf129cfedafcb083655a1780e4be994621086f780a66d9720e77163d36147051::server:aa2837148e402f675604a56602a5bbf8"
}
ok: [server2] => {
    "msg": ""
}

My host file:

[p6dualstackservers]
server1 ansible_ssh_host=10.63.60.220
server2 ansible_ssh_host=10.63.60.221

And I have the following host_vars files assigned:

server1.yml:

server_role: master

server2.yml:

server_role: node

I've tried assigning the nodeToken variable inside of k3sInstall/vars/main.yml as well as one level up from the k3sInstall role inside group_vars/all.yml but that didn't help.

I tried searching for a way to use block-level variables but couldn't find anything.

Answer 1

Using when in this use case is probably not the best fit, you would probably be better delegating some tasks to the so-called master server.

What you can do to define what server is the master, based on your inventory variable, is to delegate a fact to localhost, for example.

Then again, to get the token from your file in the master server, you can delegate this task and fact only to this server.

---

Given the playbook:

- hosts: all
  gather_facts: no

  tasks:
    - set_fact:
        master_node: "{{ inventory_hostname }}"
      when: server_role == 'master'
      delegate_to: localhost
      delegate_facts: true

    - set_fact:
        token: 12345678
      run_once: true
      delegate_to: "{{ hostvars.localhost.master_node }}"
      delegate_facts: true

    - debug:
        var: hostvars[hostvars.localhost.master_node].token
      when: server_role != 'master'

This yields the expected:

PLAY [all] ********************************************************************************************************

TASK [set_fact] ***************************************************************************************************
skipping: [node1]
ok: [node2 -> localhost]
skipping: [node3]

TASK [set_fact] ***************************************************************************************************
ok: [node1 -> node2]

TASK [debug] ******************************************************************************************************
skipping: [node2]
ok: [node1] => 
  hostvars[hostvars.localhost.master_node].token: '12345678'
ok: [node3] => 
  hostvars[hostvars.localhost.master_node].token: '12345678'

PLAY RECAP ********************************************************************************************************
node1                      : ok=2    changed=0    unreachable=0    failed=0    skipped=1    rescued=0    ignored=0   
node2                      : ok=1    changed=0    unreachable=0    failed=0    skipped=1    rescued=0    ignored=0   
node3                      : ok=1    changed=0    unreachable=0    failed=0    skipped=1    rescued=0    ignored=0