Ansible role post tasks

ansible

Is it possible to have "post tasks" in a role? i.e tasks defined in a role, that would run at the end of the play?

For example, I have a common role, which most other roles depend on. The common role provides some basic stuff to avoid repetition, such as tweaks to yum config, etc.

I notice that playbooks have post_tasks. I was wondering if it is possible to define post tasks in roles themselves?

Update:
Quoting the Ansible documentation:

Handlers: Running Operations On Change

…

These ‘notify’ actions are triggered at the end of each block of tasks
in a playbook, and will only be triggered once even if notified by
multiple different tasks.

…

Roles are described later on. It’s worthwhile to point out that
handlers are automatically processed between ‘pre_tasks’, ‘roles’,
‘tasks’, and ‘post_tasks’ sections.

…

Evidently this part of the documentation is either misleading, or down right lying (=there is an error in it). It appears that handlers are fired at the end of each play, between the tasks and post_tasks, as this following simple test shows:

- name:         Handlers test
  hosts:        all
  gather_facts: no
  roles:
    - some-role
    # some-role depends on common
  tasks:
    - name:  This a task
      shell: /bin/true
  post_tasks:
    - name:  This is a post task
      shell: /bin/true

And the common role:

# tasks/main.yml

- name:   Registering handler
  shell:  /bin/true
  notify: this is a handler


#handlers/main.yml

- name:   this is a handler
  shell:  /bin/true

(Since nobody provided an answer I can't accept one, but didn't feel right answering my own question with tips from the comments…)

Best Answer

This behavior is caused by a bug in Ansible 1.9.x, it's currently tracked here: https://github.com/ansible/ansible/issues/12575

Related Solutions

Callbacks or hooks, and reusable series of tasks, in Ansible roles

I'm not familiar with PostgreSQL so I'm unsure of the contents of the various configuration files you mentioned, but if you need to allow multiple roles to contribute to a single configuration file, I've accomplished this in one of two ways depending on what the configuration file supports:

Use a configuration file with lots of include statements to include additional configuration files located in sub-directories. This works well with something like Apache for rewrite rules, application-specific configuration directives, and virtual hosts.
Assemble the configuration file from multiple partial configuration files stored in a directory using the assemble module. I've used this method to construct a master.cf file for Postfix as I had a postfix role and another role that needed to add to the Postfix master.cf file. So I modified the postfix role to create a /etc/postfix/master.d directory and a handler that assembles the files in that directory into a master.cf file. Unfortunately, as you pointed out, since I can't call the handler in the postfix role from another role, I had to duplicate that handler in my additional role. It's slightly less than idea but it works and it's idempotent.

Are Ansible handlers defined in roles ran after the entire playbook or the role

Handlers are executed:

at the end of a play (not playbook)
on executing the meta: flush_handlers task

So "to add a 6 role to the end that needs to have the handlers of the 4th role" you need:

either to split the role assignment into separate plays;

or add a meta task and include the 6th role with include_role module:

roles:
  - role4
tasks:
  - meta: flush_handlers
  - include_role:
      name: role6

For your use case, I'd suggest the first method as the include_role module is still very fresh and there are quirks when using it (see this question on SO).

Moreover, please notice that handlers' names and listen calls are global, so two handlers in separate roles will be in conflict if they had the same name and both roles were assigned in a single play. (ref. Handlers: Running Operations On Change)

Handlers [ ] are referenced by a globally unique name, and are notified by notifiers. [ ] a handler, it will run only once, after all of the tasks complete in a particular play.

Handler names and listen topics live in a global namespace.

Empirical proof (run this shell script to confirm handlers are executed at the end of the play - there were contradicting comments and answers here):

#!/bin/bash

mkdir -p ./sf831880/roles/role1
mkdir -p ./sf831880/roles/role1/handlers
mkdir -p ./sf831880/roles/role1/tasks
mkdir -p ./sf831880/roles/role2
mkdir -p ./sf831880/roles/role2/handlers
mkdir -p ./sf831880/roles/role2/tasks

cat >./sf831880/roles/role1/tasks/main.yml <<TASKS1_END
---
- name: Always true in role1
  command: echo role1
  notify: handler1
TASKS1_END

cat >./sf831880/roles/role2/tasks/main.yml <<TASKS2_END
---
- name: Always true in role2
  command: echo role2
  notify: handler2
TASKS2_END

cat >./sf831880/roles/role1/handlers/main.yml <<HANDLERS1_END
---
- name: handler1
  debug:
    msg: "This is a handler in role1"
HANDLERS1_END

cat >./sf831880/roles/role2/handlers/main.yml <<HANDLERS2_END
---
- name: handler2
  debug:
    msg: "This is a handler in role2"
HANDLERS2_END

cat >./sf831880/playbook.yml <<PLAYBOOK_END
---
- hosts: localhost
  gather_facts: no
  connection: local
  roles:
    - role1
    - role2
  tasks:
    - debug:
        msg: "This is a task in a play"
PLAYBOOK_END

ansible-playbook ./sf831880/playbook.yml

Result:

PLAY [localhost] ***************************************************************

TASK [role1 : Always true in role1] ********************************************
changed: [localhost]

TASK [role2 : Always true in role2] ********************************************
changed: [localhost]

TASK [debug] *******************************************************************
ok: [localhost] => {
    "msg": "This is a task in a play"
}

RUNNING HANDLER [role1 : handler1] *********************************************
ok: [localhost] => {
    "msg": "This is a handler in role1"
}

RUNNING HANDLER [role2 : handler2] *********************************************
ok: [localhost] => {
    "msg": "This is a handler in role2"

Play modified to contain meta: flush_handlers:

---
- hosts: localhost
  gather_facts: no
  connection: local
  roles:
    - role1
    - role2
  tasks:
    - meta: flush_handlers
    - debug:
        msg: "This is a task in a play"

The result:

PLAY [localhost] ***************************************************************

TASK [role1 : Always true in role1] ********************************************
changed: [localhost]

TASK [role2 : Always true in role2] ********************************************
changed: [localhost]

RUNNING HANDLER [role1 : handler1] *********************************************
ok: [localhost] => {
    "msg": "This is a handler in role1"
}

RUNNING HANDLER [role2 : handler2] *********************************************
ok: [localhost] => {
    "msg": "This is a handler in role2"
}

TASK [debug] *******************************************************************
ok: [localhost] => {
    "msg": "This is a task in a play"

Handlers: Running Operations On Change

Best Answer

Related Solutions

Callbacks or hooks, and reusable series of tasks, in Ansible roles

Are Ansible handlers defined in roles ran after the entire playbook or the role

Related Topic