Ansible playbook doesnt get values from inventory group_vars - ansible

Question

I have got a simple playbook:
- hosts: all
serial: 1
order: "{{ run_order }}"
gather_facts: false
tasks:
- ping:
register: resultt
My inventory tree:
.
├── group_vars
│   └── g1
│   └── values.yml
├── host_vars
└── inv
inv file:
[g1:children]
m1
m2
[g2:children]
m3
m4
[m1]
192.168.0.60
[m2]
192.168.0.61
[m3]
192.168.0.62
[m4]
192.168.0.63
group_vars/g1/values.yml:
---
run_order: 'reverse_sorted'
When I try to run playbook:
ansible-playbook -i inv-test/inv --limit='g1' my-playbook.yml
I get the error:
ERROR! The field 'order' has an invalid value, which includes an undefined variable. The error was: 'run_order' is undefined
The error appears to be in '/home/mk/throttle': line 1, column 3, but may
be elsewhere in the file depending on the exact syntax problem.
The offending line appears to be:
- hosts: all
^ here
Although the output from ansible-inventory -i inv --graph --vars is correct
Why ansible doesn't parse vars from inventory groups_vars?
Ansible version 2.10.15

Answer 1

The problem is that you want to use a host variable in the scope of a play. See Scoping variables. It's possible if you create such a host variable first. Then you can use hostvars to reference the host variable. For example, given the simplified inventory
shell> cat hosts
[g1]
host_01
host_02
and the group_vars
shell> cat group_vars/g1.yml
run_order: 'reverse_sorted'
The playbook
shell> cat pb.yml
- hosts: all
gather_facts: false
tasks:
- debug:
var: run_order
gives (abridged)
shell> ansible-playbook -i hosts pb.yml
ok: [host_01] =>
run_order: reverse_sorted
ok: [host_02] =>
run_order: reverse_sorted
But, the playbook below
shell> cat pb.yml
- hosts: all
gather_facts: false
order: "{{ run_order }}"
tasks:
- debug:
var: run_order
fails because the variable run_order is not defined in the scope of the play
ERROR! The field 'order' has an invalid value, which includes an undefined variable. The error was: 'run_order' is undefined
The (awkward) solution is to create the hostvars in the first play and use it in the second play. For example, the second play in the playbook below is executed in the reverse order
shell> cat pb.yml
- hosts: all
gather_facts: false
tasks:
- debug:
var: run_order
- hosts: all
gather_facts: false
serial: 1
order: "{{ hostvars.host_01.run_order }}"
tasks:
- debug:
var: run_order
gives
shell> ansible-playbook -i hosts pb.yml
PLAY [all] ***********************************************************************************
TASK [debug] *********************************************************************************
ok: [host_01] =>
run_order: reverse_sorted
ok: [host_02] =>
run_order: reverse_sorted
PLAY [all] ***********************************************************************************
TASK [debug] *********************************************************************************
ok: [host_02] =>
run_order: reverse_sorted
PLAY [all] ***********************************************************************************
TASK [debug] *********************************************************************************
ok: [host_01] =>
run_order: reverse_sorted