Ansible如何将布尔类型转为对应字符串？兼容旧Playbook场景

为兼容旧版本Inventory逻辑，原有Playbook依赖when: cluster_allinone == "true"的字符串判断，现在需要动态设置cluster_allinone为字符串"true"或"false"，但设置后变量总是自动转为布尔类型，尝试to_json、ternary等方法均失败。

原Playbook代码 #

- name: check node count
  hosts: all:!gaop-vip-addresses
  tasks:
    - name: Get the number of nodes in group2
      set_fact:
        worker_count: "{{ groups['k8s-worker'] | length }}"

    - debug:
        var: worker_count

    - name: set cluster_allinone var
      set_fact:
        cluster_allinone: 'true'
      when: (worker_count | int) == 0

    - name: set cluster_allinone var
      set_fact:
        cluster_allinone: 'false'
      when: (worker_count | int) > 0

    - debug:
        var: cluster_allinone

    - debug:
        msg: single
      when: cluster_allinone == "true"

    - debug:
        msg: mutil
      when: cluster_allinone == "false"

尝试过的无效方法 #

- name: set cluster_allinone var
      set_fact:
        temp: 'true'
      when: (worker_count | int) == 0

    - name: set cluster_allinone var
      set_fact:
        temp: 'false'
      when: (worker_count | int) > 0

--- try but fail ---

    - name: set cluster_allinone var
      set_fact:
        cluster_allinone: "{{ temp | to_json }}"

    - name: set cluster_allinone var
      set_fact:
        cluster_allinone: "{{ (worker_count | int) == 0 }}"

    - name: set cluster_allinone var
      set_fact:
        cluster_allinone: "{{ temp | ternary('true', 'false') }}"

当前Ansible版本 #

ansible 2.4.5.0
  config file = /data/ansible.cfg
  configured module search path = [u'/root/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /data/ansible/lib/ansible
  executable location = /data/ansible/bin/ansible
  python version = 2.7.12 (default, Nov 19 2018, 06:48:02) [GCC 5.4.0 20160609]

解决方案 #

在Ansible 2.4.5中，set_fact会自动将字符串'true'/'false'转换为布尔类型，解决方法是直接用Jinja2条件表达式生成字符串，避免类型自动转换：

- name: check node count
  hosts: all:!gaop-vip-addresses
  tasks:
    - name: Get the number of nodes in group2
      set_fact:
        worker_count: "{{ groups['k8s-worker'] | length }}"

    - debug:
        var: worker_count

    # 直接用条件表达式生成字符串，避免自动转布尔
    - name: Set cluster_allinone as string type
      set_fact:
        cluster_allinone: "{{ 'true' if (worker_count | int) == 0 else 'false' }}"

    - debug:
        msg: "Type: {{ cluster_allinone | type_debug }}, Value: {{ cluster_allinone }}"

    - debug:
        msg: single
      when: cluster_allinone == "true"

    - debug:
        msg: mutil
      when: cluster_allinone == "false"

说明 #

• 用Jinja2的if-else表达式直接生成字符串值，绕过set_fact的自动类型转换逻辑；
• 可以用type_debug过滤器验证变量类型，确保是str而非bool；
• 此方法无需修改原有Playbook的判断逻辑，直接覆盖变量即可。

内容的提问来源于stack exchange，提问作者HuaJFrame