如何动态更改传递给剧本的额外变量

Question

我正在尝试根据条件在一组主机上安装软件。执行播放后，我想计算安装发生的主机数和跳过的主机数。

我试过在像下面这样调用任务之前在 play 中声明一个变量，但是每个主机的变量都被覆盖了，所以我无法获得实际计数：它总是 1 或 0

播放：

- name: Install Junos OS
  hosts: reachable_a_hosts
  connection: local
  gather_facts: no
  roles:
    - Juniper.junos
  vars:
    credentials:
      host: "{{ loopback_v4 }}"
      username: "username"
    
      port: "{{ port }}"
      timeout: 60
  tasks:
  - name: Extra variable test
      debug:
        msg: "upgrade count {{ upgrade_count }}"
  - name: OS Install
    import_role:
      name: os_install
      tasks_from: change__os
  - name: debug
    debug:
      msg: "upgrade count {{ upgrade_count }}"

任务：

---
- name: Increment installation count
  set_fact:
    upgrade_count : ( {{ upgrade_count|int + 1|int }} )
  when: switch_os_version != OS_version

输出：

TASK [debug] *************************************
ok: [site1] => {
    "msg": "upgrade count (1)"
}
ok: [site2] => {
    "msg": "upgrade count (1)"
}

所以我使用 -e 将变量作为命令行传递。现在输出总是0，不管条件是否满足

更新输出

TASK [os_install : Increment installation count] *********************
ok: [site1]
ok: [site2]


TASK [debug] *************************************
ok: [site1] => {
    "msg": "upgrade count 0"
}
ok: [site2] => {
    "msg": "upgrade count 0"
}

有人可以帮助我使变量的行为像全局的那样，以便我可以获得实际计数吗？

Answer 1

要解决此问题，您可以使用 ansible 寄存器，当您想要将任务的输出捕获到变量 时，可以使用 Ansible 寄存器。然后，您可以将这些寄存器的值用于不同的场景，例如条件语句、日志记录等。示例：

---
- name: Increment installation count
  set_fact:
    upgrade_count : ( {{ upgrade_count|int + 1|int }} )
  register: upgrade_count # add this line
  when: switch_os_version != OS_version

和剧本：

- name: Install Junos OS
  hosts: reachable_a_hosts
  connection: local
  gather_facts: no
  roles:
    - Juniper.junos
  vars:
    credentials:
      host: "{{ loopback_v4 }}"
      username: "username"
    
      port: "{{ port }}"
      timeout: 60
  tasks:
  - name: Extra variable test
      debug:
        msg: "upgrade count {{ upgrade_count }}"
  - name: OS Install
    import_role:
      name: os_install
      tasks_from: change__os
  - name: debug
    debug:
      msg: "upgrade count {{ upgrade_count }}"

有关详细信息，请访问此 example

Answer 2

如您所见，set_fact 是....设置事实，即设置播放循环中特定于当前目标主机的变量值。此外，正如我的评论中所报告的那样，在播放过程中无法更改额外的变量，因为它们具有最高的 level of precedence。 None 这些将适合您尝试做的计数器。

同时，有多种方法可以实现您的要求。一个简单的 IMO。

选择一个您知道主机上不存在的变量。例如，我将选择 _OS_upgraded
在每台机器上将此 var 设置为 true，installed/upgraded，false 过时。您可以删除 when 子句并直接设置测试结果。
```
- name: Set info about upgrade.
  set_fact:
    _OS_upgraded: "{{ switch_os_version != OS_version }}"
```

完成后，您可以使用 magic variable hostvars 和一些过滤器轻松计算主机数量

- name: Give some info about the tasks
  vars:
    processed_hosts: "{{ hostvars | dict2items | selectattr('value._OS_upgraded', 'defined') | list }}"
    num_host: "{{ processed_hosts | count }}"
    upgraded_hosts: "{{ processed_hosts | selectattr('value._OS_upgraded') | list | count }}"
    untouched_hosts: "{{ processed_hosts | rejectattr('value._OS_upgraded') | list | count }}"
    message: |-
      We processed {{ num_host }} hosts
      {{ upgraded_hosts }} were upgraded
      {{ untouched_hosts }} were left alone
  debug:
    msg: "{{ message.split('\n') }}"

如何动态更改传递给剧本的额外变量

How can I dynamically change the extra vars passed to playbook

ansible

ansible-2.x

junos-automation