ansible - how to iterate children groups in ansible? [closed] - ansible

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I do have an inventory file as below
[ParentGroup]
ChildrenGroup1
ChildrenGroup2
[ChildrenGroup1]
host1
host2
host3
[ChildrenGroup2]
host4
host5
host6
Now i want to iterate Children wise..
i.e. Perform my task in parallel on host1,host2, host3 i.e only on hosts exists inChildrenGroup1 and once this is success, i Need to go with ChildrenGroup2 i.e on host4, host5, host6
Points to be taken care ?
if there is any failure on any one of the childrengroup hosts then we need to wait/pause before proceeding with next children group
I shall have many children groups on my inventory
I need to action my task only on one chidlrengroup at a time.
I shall make sure all the childrengroups are addressed in one-shot too.
Can you suggest on how to take this forward ?

Answer 1

The critical limitation here is the fact that a playbook can't start another playbook. The only option is import_playbook. Imported files must be available when a playbook starts. As a result, the solution is a two-step process. Create the playbooks in the first step and then run them. For example, given the inventory
shell> cat hosts
[ParentGroup:children]
ChildrenGroup1
ChildrenGroup2
[ChildrenGroup1]
host1
host2
host3
[ChildrenGroup2]
host4
host5
host6
you want to run the playbook pb.yml as described in the question. Take the playbook and create the template by putting {{ item }} to hosts:
shell> cat pb.yml.j2
- hosts: "{{ item }}"
gather_facts: false
tasks:
- debug:
msg: "{{ inventory_hostname }}: Playbook started."
1. Create playbooks
The playbook below creates the list of the groups my_groups in the first task. Then the template task iterates this list and creates playbooks for the groups. The next template task imports these playbooks into the playbook pb-groups.yml
shell> cat pb-init.yml
- hosts: localhost
vars:
groups_other: [ParentGroup, all, ungrouped]
tasks:
- set_fact:
my_groups: "{{ groups.keys()|difference(groups_other) }}"
- template:
src: pb.yml.j2
dest: "pb-{{ item }}.yml"
loop: "{{ my_groups }}"
- template:
src: pb-groups.yml.j2
dest: pb-groups.yml
shell> cat pb-groups.yml.j2
- hosts: localhost
gather_facts: false
{% for group in my_groups %}
- import_playbook: pb-{{ group }}.yml
{% endfor %}
See created files
shell> cat pb-ChildrenGroup1.yml
- hosts: "ChildrenGroup1"
gather_facts: false
tasks:
- debug:
msg: "localhost: Playbook started."
shell> cat pb-ChildrenGroup2.yml
- hosts: "ChildrenGroup2"
gather_facts: false
tasks:
- debug:
msg: "localhost: Playbook started."
shell> cat pb-groups.yml
- hosts: localhost
gather_facts: false
- import_playbook: pb-ChildrenGroup1.yml
- import_playbook: pb-ChildrenGroup2.yml
2. Run created playbooks
shell> ansible-playbook pb-groups.yml
PLAY [localhost] ****
PLAY [ChildrenGroup1] ****
TASK [debug] ****
ok: [host1] =>
msg: 'localhost: Playbook started.'
ok: [host2] =>
msg: 'localhost: Playbook started.'
ok: [host3] =>
msg: 'localhost: Playbook started.'
PLAY [ChildrenGroup2] ****
TASK [debug] ****
ok: [host4] =>
msg: 'localhost: Playbook started.'
ok: [host5] =>
msg: 'localhost: Playbook started.'
ok: [host6] =>
msg: 'localhost: Playbook started.'
PLAY RECAP ****
...
Many children groups on my inventory
Change the inventory. For example
shell> cat hosts
[ParentGroup:children]
ChildrenGroup1
ChildrenGroup2
ChildrenGroup3
[ChildrenGroup1]
host1
host2
[ChildrenGroup2]
host4
host5
[ChildrenGroup3]
host3
host6
The commands below work as expected
shell> ansible-playbook pb-init.yml
...
shell> ansible-playbook pb-groups.yml
PLAY [localhost] ****
PLAY [ChildrenGroup1] ****
TASK [debug] ****
ok: [host1] =>
msg: 'localhost: Playbook started.'
ok: [host2] =>
msg: 'localhost: Playbook started.'
PLAY [ChildrenGroup2] ****
TASK [debug] ****
ok: [host4] =>
msg: 'localhost: Playbook started.'
ok: [host5] =>
msg: 'localhost: Playbook started.'
PLAY [ChildrenGroup3] ****
TASK [debug] ****
ok: [host3] =>
msg: 'localhost: Playbook started.'
ok: [host6] =>
msg: 'localhost: Playbook started.'
PLAY RECAP ****
...