ansible task doesn't resolve variable - ansible

Question

I'm trying to get VG_Name using below code. I can see variable value using debug:var but it doesn't work inside actual task & print value as "vg": "hostvars[inventory_hostname].ansible_lvm.lvs.varlog.vg"
tasks:
- set_fact:
LV_name: "opt"
- name: Get VG Name
set_fact:
vg_command: "{{ 'hostvars[inventory_hostname].ansible_lvm.lvs.'+ LV_name +'.vg' }}"
- name: Show VG
debug:
var: "{{ vg_command }}"
- name: extend logical volume and file system
community.general.lvol:
vg: "{{ vg_command }}"
lv: "{{ LV_name }}"
size: +100%FREE
resizefs: yes
Output:
TASK [Get VG Name] *********************************************************************************************************************************************************************************
task path: /root/ansible_disk/disk_extend.yml:92
ok: [SERVER-NAME] => {
"ansible_facts": {
"vg_command": "hostvars[inventory_hostname].ansible_lvm.lvs.varlog.vg"
},
"changed": false
}
TASK [Show VG] *************************************************************************************************************************************************************************************
task path: /root/ansible_disk/disk_extend.yml:96
ok: [SERVER-NAME] => {
"hostvars[inventory_hostname].ansible_lvm.lvs.varlog.vg": "vg_00"
}
TASK [extend logical volume and file system] *******************************************************************************************************************************************************
task path: /root/ansible_disk/disk_extend.yml:109
fatal: [SERVER-NAME]: FAILED! => {
"changed": false,
"err": " Volume group name \"hostvars[inventory_hostname].ansible_lvm.lvs.varlog.vg\" has invalid characters.\n Cannot process volume group hostvars[inventory_hostname].ansible_lvm.lvs.varlog.vg\n",
"invocation": {
"module_args": {
"active": true,
"force": false,
"lv": "varlog",
"opts": null,
"pvs": null,
"resizefs": true,
"shrink": true,
"size": "+100%FREE",
"snapshot": null,
"state": "present",
"thinpool": null,
"vg": "hostvars[inventory_hostname].ansible_lvm.lvs.varlog.vg"
}
},
"msg": "Volume group hostvars[inventory_hostname].ansible_lvm.lvs.varlog.vg does not exist.",
"rc": 5
}
Tried all possible ways(lookup, vars etc) that I could think of but no luck, any help would be appreciated!

Answer 1

You are building your string incoorectly, leaving inventory[hostname] inside the single quotes, it will be treated as a literal; so:
vg_command: "{{ 'hostvars[inventory_hostname].ansible_lvm.lvs.'+ LV_name +'.vg' }}"
should instead be:
vg_command: "{{ hostvars[inventory_hostname].ansible_lvm.lvs[LV_name].vg }}"