Ansible how to assign new value to extra vars value - variables

Question

Tower: 3.2.3
Ansible 2.4.2
I have a Tower playbook where a value is assigned lets say build_cl: latest. This is defined in the Ansible Tower's survey, which I believe is regarded as extra-vars. I have a task that performs a check, and if condition is right I need to modify the value of build_cl.
So lets say when Tower playbook is kicked off the var is:
build_cl: latest
Then:
- name: "Get latest installed CL on groups['Healthcheck_Host'][0]"
shell: |
grep -oP '(?<=\:)(.*?)(?=\-)' {{ latest_deployed_build_dir.stdout }}/buildinfo.txt
register: latest_deployed_cl
- debug:
var: latest_deployed_cl
- set_fact:
build_cl: "{{ latest_deployed_cl.stdout }}"
cacheable: yes
- debug:
var: build_cl
I have tested and the debug for the first task here returns lets say 123456.
However I try to use the set_fact module, but the second debug output still gives: latest.
Nothing I try seems to be effecting the original value. Help would be greatly appreciated. Thanks

Answer 1

Extra vars (i.e. vars passed on the command line with the -e option), have the highest precedence and cannot be changed during playbook life. set_fact will not throw any error but the value will remain the one passed at launch.
Here is a quick example to illustrate:
---
- name: Immutable extra var demo
hosts: localhost
gather_facts: false
vars:
test_var: value set in playbook var
tasks:
- name: debug var value at playbook start
debug:
var: test_var
- name: change var value
set_fact:
test_var: value set in set_fact
- name: debug var value at playbook end
debug:
var: test_var
Without extra var:
$ ansible-playbook test.yml
PLAY [Immutable extra var demo] ********************************************************************************************************************************************************************************************************
TASK [debug var value at playbook start] ***********************************************************************************************************************************************************************************************
ok: [localhost] => {
"test_var": "value set in playbook var"
}
TASK [change var value] ****************************************************************************************************************************************************************************************************************
ok: [localhost]
TASK [debug var value at playbook end] *************************************************************************************************************************************************************************************************
ok: [localhost] => {
"test_var": "value set in set_fact"
}
PLAY RECAP *****************************************************************************************************************************************************************************************************************************
localhost : ok=3 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
With extra var:
$ ansible-playbook test.yml -e "test_var='value set in extra vars'"
PLAY [Immutable extra var demo] ********************************************************************************************************************************************************************************************************
TASK [debug var value at playbook start] ***********************************************************************************************************************************************************************************************
ok: [localhost] => {
"test_var": "value set in extra vars"
}
TASK [change var value] ****************************************************************************************************************************************************************************************************************
ok: [localhost]
TASK [debug var value at playbook end] *************************************************************************************************************************************************************************************************
ok: [localhost] => {
"test_var": "value set in extra vars"
}
PLAY RECAP *****************************************************************************************************************************************************************************************************************************
localhost : ok=3 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0