Ansible Playbook遇不可达主机时Jinja2逻辑执行失败求助

当清单内存在不可达主机时，check uptime Play会因ignore_unreachable: yes跳过该主机的uptime采集任务，导致对应主机的hostvars中没有up_time变量，邮件任务的Jinja2模板直接访问servervars.up_time.stdout就会触发变量未定义错误。以下是两种可行的修复方案：

方案一：在Jinja2模板中增加变量存在性检查 #

遍历主机时先判断up_time变量是否存在，再执行后续的数值判断，避免访问不存在的属性：

- name: send mail
  hosts: localhost
  gather_facts: no
  become: no
  tasks:
    - name: Communication on high uptime servers
      mail:
        host: relay.cust.services
        port: 25
        from: abc@xyz.com
        to: abc@xyz.com
        subject: Communication on high uptime servers
        body: |-
          {% for server, servervars in hostvars.items() %}
          {% if servervars.up_time is defined %}
            {% if servervars.up_time.stdout |int >= 10 %}
               Consider rebooting the server **{{ server }}** for better performance as it has high uptime of days: {{ servervars.up_time.stdout }}
            {% endif %}
          {% endif %}
          {% endfor %}

方案二：仅遍历可达主机组 #

利用之前group_by模块生成的host_status_success组（仅包含可达主机），直接遍历该组主机，完全避开不可达主机的变量问题：

- name: send mail
  hosts: localhost
  gather_facts: no
  become: no
  tasks:
    - name: Communication on high uptime servers
      mail:
        host: relay.cust.services
        port: 25
        from: abc@xyz.com
        to: abc@xyz.com
        subject: Communication on high uptime servers
        body: |-
          {% for server in groups['host_status_success'] %}
            {% set servervars = hostvars[server] %}
            {% if servervars.up_time.stdout |int >= 10 %}
               Consider rebooting the server **{{ server }}** for better performance as it has high uptime of days: {{ servervars.up_time.stdout }}
            {% endif %}
          {% endfor %}

额外优化建议 #

可以将check uptime Play的目标主机改为host_status_success，避免对不可达主机执行无用任务：

- name: check uptime
  hosts: host_status_success
  gather_facts: no
  ignore_unreachable: yes
  become: no
  tasks:
    - name: check uptime
      raw: uptime |awk '{print $3}'
      register: up_time

内容的提问来源于stack exchange，提问作者Sharma