Jinja2 模板 if 语句未正确评估

Question

我有一个 Jinja2 模板，作为电子邮件的一部分发送 post 使用 Ansible 修补服务器。在其中我有一个 if 语句，它应该验证是否拍摄了快照。这是剧本中设置要评估的变量的部分：

- name: Was a snapshot taken
  set_fact:
    snapshot: "{{ 'yes' if (snap_result is changed and snap_result is not failed) else 'no'}}"

这是模板：

**********************************************************
PATCH REPORT FOR {{ inventory_hostname }}
DATE: {{ ansible_date_time.date }}
TIME: {{ ansible_date_time.time }}
----------------------------------------------------------
{# Determine boot message #}
{% if booted == "yes" %}
  {% set boot_message = "The system rebooted!" %}
  {% set boot_message2 = "" %}
{% else %}
  {% set boot_message = "The system did NOT reboot!" %}
  {% set boot_message2 = "Either no reboot was required OR their was an issue." %}
{% endif %}

{# Determine Snapshot Message #}
{% if snapshot == "yes" %}
  {% set snapshot_message = "A snapshot was taken of your machine." %}
  {% set snapshot_message2 = "Contact DC Operations to delete the snapshot when you are satisfied all is well." %}
{% else %}
  {% set snapshot_message = "A snapshot was NOT taken of your machine." %}
  {% set snapshot_message2 = "None was requested or it failed." %}
{% endif %}

Vendor:                 {{ ansible_system_vendor }}
Server Type:            {{ ansible_product_name }}
BIOS Version:           {{ ansible_bios_version }}
O/S Distribution:       {{ ansible_distribution }}
Previous Dist rev:      {{ pre_patch_dist | to_nice_json }}
Upgraded Dist rev:      {{ ansible_distribution_version }}
Previous Kernel rev:    {{ pre_patch_kern|to_nice_json }}
Upgraded Kernel rev:    {{ ansible_kernel }}
Python Version:         {{ ansible_python_version }}
PrePatch Uptime:        {{ pre_uptime.stdout|to_nice_json }}
PostPatch Uptime:       {{ post_uptime.stdout|to_nice_json }}

{{ boot_message }}
{{ boot_message2 }}
{{ snapshot_message }}
{{ snapshot_message2 }}
{{ snapshot }}
System took {{ elapsed_boot_time }} seconds to reboot.
----------------------------------------------------------
******** END REPORT FOR {{ inventory_hostname }} *********

结果如下：

**********************************************************
PATCH REPORT FOR na2-dvanstst06
DATE: 2021-04-07
TIME: 10:48:26
----------------------------------------------------------
    
    
Vendor:                 VMware, Inc.
Server Type:            VMware Virtual Platform
BIOS Version:           6.00
O/S Distribution:       Ubuntu
Previous Dist rev:      "18.04"
Upgraded Dist rev:      18.04
Previous Kernel rev:    "4.15.0-132-generic"
Upgraded Kernel rev:    4.15.0-132-generic
Python Version:         3.6.9
PrePatch Uptime:        " 10:48:20 up 5 days, 23:21,  1 user,  load average: 1.01, 1.00, 1.00"
PostPatch Uptime:       " 10:48:27 up 5 days, 23:22,  1 user,  load average: 1.01, 1.00, 1.00"

The system did NOT reboot!
Either no reboot was required OR their was an issue.
A snapshot was NOT taken of your machine.
None was requested or it failed.
Snapshot value is True
Booted value is False
System took 0 seconds to reboot.
----------------------------------------------------------
******** END REPORT FOR na2-dvanstst06 *********

正如您在模板末尾看到的，我输入了 snapshot 和 booted 的值，以查看它们的评估是否相同。由于机器不需要重新启动 booted 评估正确。但是，即使 snapshot 为真，它也将其视为假。我哪里错了？

Answer 1

我认为您是在强制检查模板中的字符串文字 "yes"。而 set_fact 将 'yes' 设置为布尔值。看到这个 .

因此 snapshot 变量是布尔值 True 而不是您期望的字符串 'yes'。

这表示为：

Snapshot value is True

因此，针对 if 条件对模板进行简单更改即可解决问题：

{% if snapshot %}
  {% set snapshot_message = "A snapshot was taken of your machine." %}
  {% set snapshot_message2 = "Contact DC Operations to delete the snapshot when you are satisfied all is well." %}
{% else %}
  {% set snapshot_message = "A snapshot was NOT taken of your machine." %}
  {% set snapshot_message2 = "None was requested or it failed." %}
{% endif %}

同样适用于 boot 变量。您可以将其设置为布尔值 True/False 并相应地使用 if 条件。

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