ansible v2_runner_on_start 能写一些什么东西，给些案例

当 Ansible 开始执行任务时，可以在 playbook 或 role 中使用 `v2_runner_on_start` 这个钩子（hook）来执行一些额外的操作。下面是一些使用 `v2_runner_on_start` 钩子的案例：

1. 在任务开始时发送通知

- name: Send notification on task start
  hosts: all
  tasks:
    - name: Notify on task start
      local_action:
        module: slack
        token: "{{ slack_token }}"
        msg: "Ansible task {{ ansible_playbook_name }} started on {{ inventory_hostname }}"
      delegate_to: localhost

  handlers:
    - name: Restart service
      service:
        name: myservice
        state: restarted

2. 在任务开始时记录日志

- name: Log task start
  hosts: all
  tasks:
    - name: Log task start
      local_action:
        module: log
        msg: "Ansible task {{ ansible_playbook_name }} started on {{ inventory_hostname }}"
      delegate_to: localhost

  handlers:
    - name: Restart service
      service:
        name: myservice
        state: restarted

3. 在任务开始时设置全局变量

- name: Set global variable on task start
  hosts: all
  tasks:
    - name: Set global variable
      set_fact:
        myvar: "myvalue"
      delegate_to: localhost
      run_once: true

  handlers:
    - name: Restart service
      service:
        name: myservice
        state: restarted

这些案例只是示例，实际上你可以在 `v2_runner_on_start` 钩子中执行任何 Ansible 模块或自定义模块，只要它们不会影响 Ansible 任务的正常执行即可。