callback race condition

callback_race.py

from __future__ import (absolute_import, division, print_function)

from ansible.plugins.callback import CallbackBase


class CallbackModule(CallbackBase):
    CALLBACK_VERSION = 2.0
    CALLBACK_TYPE = 'notification'
    CALLBACK_NAME = 'callback_race'

    def __init__(self):
        super(CallbackModule, self).__init__()
        self.loop_items = []

    def v2_playbook_on_task_start(self, task, is_conditional, is_handler=False):
        print("playbook_on_task_start")

    def v2_runner_item_on_ok(self, result):
        print("runner_item_on_ok")
        self.loop_items.append(result)

    def v2_runner_on_ok(self, result, **kwargs):
        print("runner_on_ok")
        print(self.loop_items)

output_with_three_items.txt

$ ansible-playbook playbook.yml 
 [WARNING]: Host file not found: /etc/ansible/hosts

 [WARNING]: provided hosts list is empty, only localhost is available


PLAY [Create fake hosts] *****************************************************************************************************************************************************************************************************************************************************************************************************

TASK [Add fake hosts in inventory] *******************************************************************************************************************************************************************************************************************************************************************************************
playbook_on_task_start
changed: [localhost] => (item=host1)
runner_item_on_ok
changed: [localhost] => (item=host2)
runner_item_on_ok
changed: [localhost] => (item=host3)
runner_item_on_ok
runner_on_ok
[<ansible.executor.task_result.TaskResult object at 0x7f7d639b2650>, <ansible.executor.task_result.TaskResult object at 0x7f7d63a8c1d0>, <ansible.executor.task_result.TaskResult object at 0x7f7d639d6ad0>]

PLAY RECAP *******************************************************************************************************************************************************************************************************************************************************************************************************************
localhost                  : ok=1    changed=1    unreachable=0    failed=0

output_with_two_items.txt

$ ansible-playbook playbook.yml 
 [WARNING]: Host file not found: /etc/ansible/hosts

 [WARNING]: provided hosts list is empty, only localhost is available


PLAY [Create fake hosts] *****************************************************************************************************************************************************************************************************************************************************************************************************

TASK [Add fake hosts in inventory] *******************************************************************************************************************************************************************************************************************************************************************************************
playbook_on_task_start
changed: [localhost] => (item=host1)
runner_item_on_ok
changed: [localhost] => (item=host2)
runner_item_on_ok
runner_on_ok
[<ansible.executor.task_result.TaskResult object at 0x7febe5456650>, <ansible.executor.task_result.TaskResult object at 0x7febe55301d0>]
changed: [localhost] => (item=host3)
runner_item_on_ok

PLAY RECAP *******************************************************************************************************************************************************************************************************************************************************************************************************************
localhost                  : ok=1    changed=1    unreachable=0    failed=0   

playbook.yml

- name: Create fake hosts
  hosts: localhost
  gather_facts: no
  tasks:
    - name: Add fake hosts in inventory
      add_host:
        name: "{{ item }}"
        ansible_host: "127.0.0.1"
        ansible_connection: "local"
      with_items:
        - host1
        - host2
        - host3