Access variable in other play - Ansible - ansible

Question

Ansible Version: 2.4.2.0
From here and here, I was able write below playbook
$ cat test.yml
- name: Finding Master VMs
hosts: all-compute-host
remote_user: heat-admin
tasks:
- name: Getting master VM's hostname
shell: hostname
register: hostname_output
- name: Access in different play
hosts: localhost
connection: local
tasks:
- name: Testing vars
debug: var='{{ hostvars[item]['hostname_output']['stdout'] }}'
with_items: groups['all-compute-host']
I don't want use gather_facts: true and access hostname from it. Getting below error when I try to above playbook
-----------OUTPUT REMOVED----------------
TASK [Testing vars] *******************************************************************************************************************
fatal: [localhost]: FAILED! => {"msg": "The task includes an option with an undefined variable. The error was: u\"hostvars['groups['all-compute-host']']\" is undefined\n\nThe error appears to have been in '/tmp/test.yml': line 18, column 5, but may\nbe elsewhere in the file depending on the exact syntax problem.\n\nThe offending line appears to be:\n\n tasks:\n - name: Testing vars\n ^ here\n\nexception type: <class 'ansible.errors.AnsibleUndefinedVariable'>\nexception: u\"hostvars['groups['all-compute-host']']\" is undefined"}
to retry, use: --limit #/tmp/test.retry
-----------OUTPUT REMOVED----------------
I tried below things
debug: var=hostvars[item]['hostname_output']['stdout']
debug: var=hostvars.item.hostname_output.stdout'
I have also tried direct host group instead of iterating item like below
debug: var=hostvars.all-compute-host.hostname_output.stdout'
debug: var=hostvars['all-compute-host']['hostname_output']['stdout']
ok: [localhost] => {
"hostvars['all-compute-host']['hostname_output']['stdout']": "VARIABLE IS NOT DEFINED!"
}
I have also try direct host name.But no use
debug: var='hostvars.compute01.hostname_output.stdout'

Answer 1

The problem is with your debug statement:
tasks:
- name: Testing vars
debug: var='{{ hostvars[item]['hostname_output']['stdout'] }}'
with_items: groups['all-compute-host']
There are two issues:
The value of the var argument to the debug module is evaluated in a Jinja templating context. That means you must not use the {{...}} template markers.
On the hand, the argument to with_items does need the {{...}} markers; without that, you're iterating over a list consisting of a single item, the literal string groups['all-compute-host'].
With both of those problems fixed (and a few minor stylistic changes), you get:
tasks:
- name: Testing vars
debug:
var: hostvars[item].hostname_output.stdout
with_items: "{{ groups['all-compute-host'] }}"