有没有一种方法可以验证Ansible库存文件中某个组的主机数量? [英] Is there a way to validate the number of hosts for a group in Ansible Inventory file?

问题描述

我的要求如下所示，我有一个Ansible库存文件，该文件根据以下所示的组件分为几组:

My requirement is shown below, I have an Ansible inventory file which is divided into some groups based on the components shown below:

[all]

node1 
node2
node3
node4

[webapp]
node3
node4

[ui]
node1

是否可以通过一种方法来验证清单文件中某个组的主机数量，如果条件失败，则不应运行剧本?

Is there a way to validate the number of hosts for a group in inventory file if condition fails then playbook should not run ?

我的条件是:ui组应该始终只有一个主机.

My condition is: ui group should always have only one host.

例如:

[ui]
node1  -- condition check pass proceed with playbook execution

[ui]
node1 
node2  -- condition fails should stop playbook execution with exception 
          with ui group cannot have more than one hosts

推荐答案

您可以轻松完成一项任务:

You can easily do it in a single task:

• 使用Ansible 使用 length过滤器对其进行组合以计算数量ui组中的元素的数量，

  combine it with length filter to count the number of elements in ui group,

  将以上内容插入 assert 或 fail 模块来验证和控制流程.

  insert the above into an arithmetic comparison conditional in assert or fail module to verify and control the flow.

  例如:

  - name: Inventory validation
    hosts: localhost
    gather_facts: false
    tasks:
      - assert:
          that:
            - "groups['ui'] | length <= 1"
            - "groups['webapp'] | length <= 1"
  

  但是(这是基于注释的)，如果您首先分配变量，则需要在比较时将值转换为整数:

  But (this is based on comment) if you assign the variables first, you need to cast the value to integer in comparison:

  - name: Inventory validation
    hosts: localhost
    gather_facts: false
    vars:
      UI_COUNT: "{{ groups['ui'] | length }}"
      WEBAPP_COUNT: "{{ groups['webapp'] | length }}"
    tasks:
      - assert:
          that:
            - "UI_COUNT | int <= 1"
            - "WEBAPP_COUNT | int <= 1"
  

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