How to use set_fact to set a new host fact based on when conditionals.

[Alex Lien]

Hi all,

I am trying to set a new host fact (is_master, is_slave) based on comparison of a pre-assigned variable and ansible_hostname fact.

group_vars/

    master_hostname: host1

    slave_hostname: host2

Tasks

- name: Set master host fact

  set_fact:

     is_master: yes

  when: master_hostname == ansible_hostname

- name: Set slave host fact

  set_fact:

     is_slave: yes

  when: slave_hostname == ansible_hostname

- name: copy master configuration file

  template:

     src: master.j2

     dest: /etc/master.conf

  when: is_master == True

- name: copy slave configuration file

  template:

     src: slave.j2

    dest: /etc/slave.conf

  when: is_slave == True

TASK [Gathering Facts] *********************************************************

ok: [host1]

ok: [host2]

TASK [Set is_master variable] ***************************************

ok: [host1]

skipping: [host1]

TASK [Set is_slave variable] ****************************************

skipping: [host2]

ok: [host2]

The goal I am trying to reach is to run certain tasks depending whether the host is master or slave. But these set_fact tasks always get skipped even though condition should be true. Really appreciate your help in pointing out what I am doing wrong.

[Pshem Kowalczyk]

You're most likely after inventory_hostname variable (not ansible_hostname).

kind regards

Pshem

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[Brian Coca]

using set_fact that way requires you to check if those vars are
defined, i believe this is a better approach:

vars:
is_master: "{{ inventory_hostname == master_hostname }}"
is_slave: "{{ inventory_hostname == master_hostname }}"

then you can just use them direcly in subsequent conditionals:

when: is_master|bool


There are other approaches as well, i.e using group_by, but I think
the one above should work best for you.
----------
Brian Coca

[Alex Lien]

Hi Brian,

I made the changes based on your suggestions and they work fine.  Thank You very much for your help.

Regards,

Alex

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