Ansible树莓派Docker主机补丁剧本：容器数对比任务异常失败排查

我正在编写Ansible剧本，为树莓派Docker主机执行补丁操作，步骤如下：

• 更新apt缓存
• 获取运行中容器
• 显示主机名及运行容器数量
• 停止容器
• 更新软件包
• 重启主机
• 再次获取运行中容器
• 显示主机名及运行容器数量
• 对比重启前后的容器数，不匹配则任务失败

现在第9步存在问题：即使重启前后容器数均为5，对比任务仍会触发失败。以下是我的main.yml代码及错误输出：

---
- name: Patching Raspberry pi
  hosts: all
  become: true
  gather_facts: true
#  vars_files:
#    ./vars/vars.yml

  pre_tasks:
    - name: Update Apt Cache
      ansible.builtin.apt:
        update_cache: true
        cache_valid_time: 3600

    - name: Get running containers
      community.docker.docker_host_info:
        containers: true
      register: docker_info

    - name: Show Number of running containers
      ansible.builtin.debug:
        msg: "Hostname - {{ docker_info.host_info.Name }} has {{ docker_info.host_info.ContainersRunning }} Containers running"
      register: docker_pre_reboot

    - name: Stop running containers
      community.docker.docker_container:
        name: "{{ item }}"
        state: stopped
      loop: "{{ docker_info.containers | map(attribute='Id') | list }}"

  tasks:
    - name: Update all packages
      ansible.builtin.apt:
        name: "*"
        state: latest

    - name: Reboot
      ansible.builtin.reboot:

    - name: Get running containers
      community.docker.docker_host_info:
        containers: true
      register: docker_info

#    - name: Check Containers are running after reboot
#      ansible.builtin.debug:
#        msg: "Hostname - {{ docker_info.host_info.Name }} has {{ docker_info.host_info.ContainersRunning }} Containers running"
#      failed_when: docker_info.host_info.ContainersRunning != docker_pre_reboot.host_info.ContainersRunning "

    - name: Compare Pre - Post Containers
      ansible.builtin.debug:
        msg: "Pre-reboot Containers {{ docker_pre_reboot.host_info.ContainersRunning }} - Post-reboot Containers {{ docker_info.host_info.ContainersRunning }}"
      failed_when: docker_info.host_info.ContainersRunning != docker_pre_reboot.host_info.ContainersRunning

错误输出：

TASK [Compare values] *************************************************************************************************************************************************
fatal: [pi-dev]: FAILED! => {
    "msg": "Pre-reboot Containers 5 - Post-reboot Containers 5"
}

问题核心在于docker_pre_reboot的注册逻辑错误：你用debug模块注册的变量，并不包含host_info字段——debug模块的注册结果是自身的输出结构，而非docker_host_info的返回值。

正确的做法是直接从docker_host_info的注册结果中提取容器数，用set_fact保存为独立变量，避免依赖debug模块的无效注册数据。

修复后的剧本示例 #

---
- name: Patching Raspberry pi
  hosts: all
  become: true
  gather_facts: true

  pre_tasks:
    - name: Update Apt Cache
      ansible.builtin.apt:
        update_cache: true
        cache_valid_time: 3600

    - name: Get running containers (pre-reboot)
      community.docker.docker_host_info:
        containers: true
      register: docker_pre_reboot_info

    - name: Save pre-reboot container count
      ansible.builtin.set_fact:
        pre_reboot_container_count: "{{ docker_pre_reboot_info.host_info.ContainersRunning }}"

    - name: Show pre-reboot container count
      ansible.builtin.debug:
        msg: "Hostname - {{ docker_pre_reboot_info.host_info.Name }} has {{ pre_reboot_container_count }} Containers running"

    - name: Stop running containers
      community.docker.docker_container:
        name: "{{ item }}"
        state: stopped
      loop: "{{ docker_pre_reboot_info.containers | map(attribute='Id') | list }}"

  tasks:
    - name: Update all packages
      ansible.builtin.apt:
        name: "*"
        state: latest

    - name: Reboot
      ansible.builtin.reboot:

    - name: Get running containers (post-reboot)
      community.docker.docker_host_info:
        containers: true
      register: docker_post_reboot_info

    - name: Show post-reboot container count
      ansible.builtin.debug:
        msg: "Hostname - {{ docker_post_reboot_info.host_info.Name }} has {{ docker_post_reboot_info.host_info.ContainersRunning }} Containers running"

    - name: Compare Pre - Post Containers
      ansible.builtin.debug:
        msg: "Pre-reboot Containers {{ pre_reboot_container_count }} - Post-reboot Containers {{ docker_post_reboot_info.host_info.ContainersRunning }}"
      failed_when: docker_post_reboot_info.host_info.ContainersRunning != pre_reboot_container_count

关键修改点 #

1. 用set_fact将预重启容器数保存为独立变量pre_reboot_container_count，确保取值直接来自docker_host_info的有效返回
2. 预重启和重启后的Docker信息使用不同变量名（docker_pre_reboot_info、docker_post_reboot_info），避免变量覆盖
3. 对比逻辑直接使用有效字段，确保数值类型和取值的准确性

修改后即可正常对比重启前后的容器数量，不会出现数值相等但任务失败的情况。

内容的提问来源于stack exchange，提问作者0lzi