Execute role in play based on a failure [duplicate] - ansible

Question

I'm trying to spin up an AWS deployment environment in Ansible, and I want to make it so that if something fails along the way, Ansible tears down everything on AWS that has been spun up so far. I can't figure out how to get Ansible to throw an error within the role
For example:
<main.yml>
- hosts: localhost
connection: local
roles:
- make_ec2_role
- make_rds_role
- make_s3_role
2. Then I want it to run some code based on that error here.
<make_rds_role>
- name: "Make it"
- rds:
params: etc <-- 1. Let's say it fails in the middle here
I've tried:
- name: this command prints FAILED when it fails
command: /usr/bin/example-command -x -y -z
register: command_result
failed_when: "'FAILED' in command_result.stderr"
As well as other things on within the documentation, but what I really want is just a way to use something like the "block" and "rescue" commands , but as far as I can tell that only works within the same book and on plays, not roles. Does anyone have a good way to do this?

Answer 1

Wrap tasks inside your roles into block/rescue thing.
Make sure that rescue block has at least one task – this way Ansible will not mark the host as failed.
Like this:
- block:
- name: task 1
... # something bad may happen here
- name: task N
rescue:
- assert: # we need a dummy task here to prevent our host from being failed
that: ansible_failed_task is defined
Recent versions of Ansible register ansible_failed_task and ansible_failed_result when hit rescue block.
So you can do some post_tasks in your main.yml playbook like this:
post_tasks:
- debug:
msg: "Failed task: {{ ansible_failed_task }}, failed result: {{ ansible_failed_result }}"
when: ansible_failed_task is defined
But be warned that this trick will NOT prevent other roles from executing.
So in your example if make_rds_role fails ansible will apply make_s3_role and run your post_tasks afterwards.
If you need to prevent it, add some checking for ansible_failed_task fact in the beginning of each role or something.