Passing variables between nested playbooks - ansible

Question

I have a playbook where I'm spinning up an instance in aws with the ec2 module. To be more flexible I ask via prompt for the hostname. I found in the ec2 examples the code snippet, which allows you to run a second playbook with newly spun up instance for further configuration.
Now I want to set the hostname via module hostname but I cannot access the variable in the second playbook.
This is how my playbook looks like:
---
- hosts: localhost
...
vars_prompt:
- name: var_hostname
prompt: "Please enter the hostname"
private: no
tasks:
- name: Spin up instance
local_action:
module: ec2
...
register: ec2
- name: Add new instance to host group
add_host: hostname={{ item.public_ip }} groupname=launched
with_items: ec2.instances
- hosts: launched
...
tasks:
- name: Set hostname
hostname: name="{{ var_hostname }}"
fatal: [launched] => One or more undefined variables: 'var_hostname' is undefined
Is there a way to pass a variable from one playbook to another one?
I found Ansible best practice for passing vars to nested playbooks? but unfortunately it didn't had a solution which I can use.

Answer 1

You can use set_fact and hostvars together to achieve what you want.
Do set_fact on one group of hosts( i.e localhost), and access them in a different play using hostvars
{{hostvars['localhost']["new_fact"]}}

Answer 2

You can use local files.
1) Write
- name: write public ip
local_action:
template:
dest: /tmp/ansible_master_public_ip.txt
src: templates/public_ip.j2
2) Retrieve with http://docs.ansible.com/ansible/playbooks_lookups.html
hostname: "{{ lookup('file', '/tmp/ansible_master_public_ip.txt') | trim }}"
PS. Ini file lookup also an option if you need more than few variables.

Answer 3

Add the host's variable to the parameters. For example,
- name: Add new instance to host group
add_host:
hostname: "{{ ec2.instances.0.public_ip }}"
groupname: launched
var_hostname: "{{ var_hostname }}"
See examples
Use only the first item from the list because you have only one hostname. There is no reason to iterate the list.
Example of a complete playbook for testing
- hosts: localhost
gather_facts: false
vars_prompt:
- name: var_hostname
prompt: "Please enter the hostname"
private: no
vars:
ec2:
instances:
- public_ip: AAA.BBB.CCC.DDD
tasks:
- name: Add new instance to host group
add_host:
hostname: "{{ ec2.instances.0.public_ip }}"
groupname: launched
var_hostname: "{{ var_hostname }}"
- hosts: launched
gather_facts: false
tasks:
- debug:
var: var_hostname
shell> ansible-playbook pb.yml
Please enter the hostname: host_2
PLAY [localhost] *****************************************************************************
TASK [Add new instance to host group] ********************************************************
changed: [localhost]
PLAY [launched] ******************************************************************************
TASK [debug] *********************************************************************************
ok: [AAA.BBB.CCC.DDD] =>
var_hostname: host_2
PLAY RECAP ***********************************************************************************
AAA.BBB.CCC.DDD: ok=1 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
localhost : ok=1 changed=1 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
Use pause instead of vars_prompt if you have more hosts. For example,
- name: Get var_hostname(s)
pause:
prompt: "Please enter the hostname for {{ item.public_ip }}"
echo: yes
loop: "{{ ec2.instances }}"
register: var_hostnames
- name: Add new instances to host group
add_host:
hostname: "{{ item.item.public_ip }}"
groupname: launched
var_hostname: "{{ item.user_input }}"
loop: "{{ var_hostnames.results }}"
loop_control:
label: "{{ item.user_input }}"
Example of a complete playbook for testing
- hosts: localhost
gather_facts: false
vars:
ec2:
instances:
- public_ip: AAA.BBB.CCC.DD1
- public_ip: AAA.BBB.CCC.DD2
tasks:
- name: Get var_hostname(s)
pause:
prompt: "Please enter the hostname for {{ item.public_ip }}"
echo: yes
loop: "{{ ec2.instances }}"
register: var_hostnames
- name: Add new instances to host group
add_host:
hostname: "{{ item.item.public_ip }}"
groupname: launched
var_hostname: "{{ item.user_input }}"
loop: "{{ var_hostnames.results }}"
loop_control:
label: "{{ item.user_input }}"
- hosts: launched
gather_facts: false
tasks:
- debug:
var: var_hostname
shell> ansible-playbook pb.yml
PLAY [localhost] *****************************************************************************
TASK [Get var_hostname(s)] *******************************************************************
[Get var_hostname(s)]
Please enter the hostname for AAA.BBB.CCC.DD1:
host_1^Mok: [localhost] => (item={'public_ip': 'AAA.BBB.CCC.DD1'})
[Get var_hostname(s)]
Please enter the hostname for AAA.BBB.CCC.DD2:
host_2^Mok: [localhost] => (item={'public_ip': 'AAA.BBB.CCC.DD2'})
TASK [Add new instances to host group] *******************************************************
ok: [localhost] => (item=host_1)
ok: [localhost] => (item=host_2)
PLAY [launched] ******************************************************************************
TASK [debug] *********************************************************************************
ok: [AAA.BBB.CCC.DD1] =>
var_hostname: host_1
ok: [AAA.BBB.CCC.DD2] =>
var_hostname: host_2
PLAY RECAP ***********************************************************************************
AAA.BBB.CCC.DD1: ok=1 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
AAA.BBB.CCC.DD2: ok=1 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
localhost : ok=2 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0