Ansible访问字典值返回空列表，未获取预期值问题咨询

编写了如下Ansible主Playbook，通过vars_files引入environment-mapping.yml变量文件，其中controller_ip_environment_map字典包含XX.XXX.X.Y对应DEV的键值对。执行Playbook后，已正确获取controller_ip为XX.XXX.X.Y，但通过controller_ip_environment_map[controller_ip]取值时，environment变量却得到空列表[]，而非预期的DEV，请问该问题原因是什么？

主Playbook代码 #

- hosts: localhost

  vars_files:
    - ../vars/environment-mapping.yml

  tasks:

    - name: echo and register controller's ip
      ansible.builtin.shell:
        cmd: |
          echo "$(hostname -I)" | sed 's/\s*$//'

      register: bash_echoed__controller_ip


    - name: set controller_ip_stringified
      set_fact:
        controller_ip: "{{ bash_echoed__controller_ip.stdout }}"


    - name: set environment
      set_fact:
        environment: "{{ controller_ip_environment_map[controller_ip] | default('unknown') }}"


    - name: show debug
      debug:
        msg:
          - "controller_ip_environment_map: {{ controller_ip_environment_map }}"
          - "controller_ip: {{ controller_ip }}"
          - "environment: {{ environment }}"

变量文件../vars/environment-mapping.yml代码 #

---

controller_ip_environment_map: {
  "XX.XXX.X.Y": "DEV",
  "XX.XXX.X.W": "TEST",
  "XX.XXX.X.Z": "PROD",
}

执行结果 #

- localhost on hosts: localhost -
Gathering Facts...
  localhost ok
echo and register controller's ip...
  localhost done | stdout: XX.XXX.X.Y
set controller_ip_stringified...
  localhost ok
set environment...
  localhost ok
show debug...
  localhost ok: {
    "changed": false,
    "msg": [
        "controller_ip: XX.XXX.X.Y",
        "controller_ip_environment_map: {'XX.XXX.X.Y': 'DEV', 'XX.XXX.X.W': 'TEST', 'XX.XXX.X.Z': 'PROD'}",
        "environment: []",

    ]
}

核心有两个问题：

1. 内置变量冲突：environment是Ansible的内置魔法变量，本身是列表类型，用于存储执行环境相关变量。尝试用自定义值覆盖它时会触发异常行为，无法正确赋值，最终返回内置变量的默认空列表。
2. IP字符串可能含隐藏空白：虽然hostname -I输出看起来是干净的IP，但实际可能包含不可见的空白字符（比如换行符、残留空格），即使通过sed处理也可能没彻底清除，导致controller_ip的值和字典中的键不完全匹配。

1. 更换自定义变量名 #

停止使用environment作为变量名，改用其他名称，比如target_env：

- name: set target environment
  set_fact:
    target_env: "{{ controller_ip_environment_map[controller_ip] | default('unknown') }}"

2. 可靠获取IP地址 #

放弃Shell命令获取IP，改用Ansible内置事实变量，更稳定且无隐藏字符：

- name: set controller_ip using ansible fact
  set_fact:
    controller_ip: "{{ ansible_default_ipv4.address }}"

如果必须用Shell命令，彻底清理所有空白：

- name: echo and register controller's ip
  ansible.builtin.shell:
    cmd: hostname -I | awk '{print $1}'
  register: bash_echoed__controller_ip

3. 验证字符串一致性 #

添加任务检查controller_ip的实际内容，确认无隐藏字符：

- name: check controller_ip content
  debug:
    msg:
      - "IP length: {{ controller_ip | length }}"
      - "IP raw content: {{ controller_ip | to_json }}"

内容的提问来源于stack exchange，提问作者Tms91