Ansible won't see a handler when using the group_by - ansible

Question

I used to have simple playbook (something like this) which I run on all over my machines (RH & Debian based) to update them, and for each machine which was updated run a script (notify handler).
Recently I tried to test a new module called group_by, so instead using the when condition to run yum update when ansible_distribution == "CentOS", I will first gather the facts and group the host based on there ansible_pkg_mgr as key and then I was looking to run yum update on all the hosts which the key is PackageManager_yum , see the play book example:
---
- hosts: all
gather_facts: false
remote_user: root
tasks:
- name: Gathering facts
setup:
- name: Create a group of all hosts by operating system
group_by: key=PackageManager_{{ansible_pkg_mgr}}
- hosts: PackageManager_apt
gather_facts: false
tasks:
- name: Update DEB Family
apt:
upgrade=dist
autoremove=yes
install_recommends=no
update_cache=yes
when: ansible_os_family == "Debian"
register: update_status
notify: updateX
tags:
- deb
- apt_update
- update
- hosts: PackageManager_yum
gather_facts: false
tasks:
- name: Update RPM Family
yum: name=* state=latest
when: ansible_os_family == "RedHat"
register: update_status
notify: updateX
tags:
- rpm
- yum
- yum_update
handlers:
- name: updateX
command: /usr/local/bin/update
And this is the error message I get,
PLAY [all] ********************************************************************
TASK [Gathering facts] *********************************************************
Wednesday 21 December 2016 11:26:17 +0200 (0:00:00.031) 0:00:00.031 ****
....
TASK [Create a group of all hosts by operating system] *************************
Wednesday 21 December 2016 11:26:26 +0200 (0:00:01.443) 0:00:09.242 ****
TASK [Update DEB Family] *******************************************************
Wednesday 21 December 2016 11:26:26 +0200 (0:00:00.211) 0:00:09.454 ****
ERROR! The requested handler 'updateX' was not found in either the main handlers list nor in the listening handlers list
thanks in advance.

Answer 1

You defined handlers only in one of your plays. It's quite clear if you look at the indentation.
The play which you execute for PackageManager_apt does not have the handlers at all (it has no access to the updateX handler defined in a separate play), so Ansible complains.
If you don't want to duplicate the code, you can save the handler to a separate file (let's name it handlers.yml) and include in both plays with:
handlers:
- name: Include common handlers
include: handlers.yml
Note: there's a remark in Handlers: Running Operations On Change section regarding including handlers:
You cannot notify a handler that is defined inside of an include. As of Ansible 2.1, this does work, however the include must be static.
Finally, you should rather consider converting your playbook to a role.
A common method to achieve what you want is to include the tasks (in tasks/main.yml) using file names with the architecture in their names:
- include: "{{ architecture_specific_tasks_file }}"
with_first_found:
- "tasks-for-{{ ansible_distribution }}.yml"
- "tasks-for-{{ ansible_os_family }}.yml"
loop_control:
loop_var: architecture_specific_tasks_file
Handlers are then defined in handlers/main.yml.