How to execute on multiple hosts in ansible - ansible

Question

I have a script that will execute in two parts. First it will execute on localhost and query a database table to get a hostname. second part of the script should run on the host which was registered in the query before. I am not able to set the host with the set_fact I did in the first part of the code.
this is what iam trying to do:
- hosts: localhost
gather_facts: false
become: yes
become_user: oracle
vars_files:
- vars/main.yml
tasks:
- name: Get new hostname
tempfile:
state: file
register: tf
- name: create sql file
template:
src: get_hostname.sql.j2
dest:"{{ tf.path }}"
mode: 0775
- name: login
command:
argv:
- "sqlplus"
- -s
- "#{{ tf.path }}"
environment:
ORACLE_HOME: "oracle/home"
register: command_out
- set_fact:
NEW_HOST: "{{ command_out.stdout }}"
- hosts: "{{ NEW_HOST }}"
gather_facts: false
become: yes
become_user: oracle
vars_file:
- vars/main.yml
tasks:
- name: debug
command: hostname
register: new_host_out
- debug:
msg: "new host is {{ new_host_out.stdout }}"
Everything works fine in the first part of the code, but errors out at the second part saying it cannot find the NEW_HOST.

Answer 1

Use hostvars to reference such a variable. Create a dummy host to keep this variable. For example, given the inventory
shell> cat hosts
dummy
[test]
test_11
test_12
test_13
The playbook creates the variable. See Delegated facts
shell> cat pb.yml
- hosts: localhost
tasks:
- set_fact:
NEW_HOST: test_12
delegate_to: dummy
delegate_facts: true
- debug:
var: hostvars.dummy.NEW_HOST
- hosts: "{{ hostvars.dummy.NEW_HOST }}"
gather_facts: false
tasks:
- debug:
var: inventory_hostname
gives
shell> ansible-playbook pb.yml
PLAY [localhost] ****************************************************************************
TASK [set_fact] *****************************************************************************
ok: [localhost -> dummy]
TASK [debug] ********************************************************************************
ok: [localhost] =>
hostvars.dummy.NEW_HOST: test_12
PLAY [test_12] ******************************************************************************
TASK [debug] ********************************************************************************
ok: [test_12] =>
inventory_hostname: test_12
PLAY RECAP **********************************************************************************
localhost: ok=2 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
test_12 : ok=1 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
You can use localhost for this purpose as well. The playbook below works as expected
- hosts: localhost
tasks:
- set_fact:
NEW_HOST: test_12
- hosts: "{{ hostvars.localhost.NEW_HOST }}"
gather_facts: false
tasks:
- debug:
var: inventory_hostname