当ansible查找失败时如何回退到默认值? [英] How to fallback to a default value when ansible lookup fails?

问题描述

我有点惊讶地发现他的代码段失败并出现 IOError 异常，而不是默认省略该值.

I was a little bit surprised to discover that his piece of code fails with an IOError exception instead of defaulting to omitting the value.

#!/usr/bin/env ansible-playbook -i localhost,
---
- hosts: localhost
  tasks:
    - debug: msg="{{ lookup('ini', 'foo section=DEFAULT file=missing-file.conf') | default(omit) }}"

如何在不引发异常的情况下加载值?

How can I load a value without raising an exception?

请注意，查找模块支持默认值参数，但这个参数对我来说没有用，因为它只有在可以打开文件时才有效.

Please note that the lookup module supports a default value parameter but this one is useless to me because it works only when it can open the file.

我需要一个即使无法打开文件也能正常工作的默认值.

I need a default value that works even when the it fails to open the file.

推荐答案

据我所知 Jinja2 很遗憾不支持任何 try/catch 机制.

As far as I know Jinja2 unfortunately doesn't support any try/catch mechanism.

所以你要么向 Ansible 团队修补 ini 查找插件/文件问题，要么使用这个丑陋的解决方法:

So you either patch ini lookup plugin / file issue to Ansible team, or use this ugly workaround:

---
- hosts: localhost
  gather_facts: no
  tasks:
    - debug: msg="{{ lookup('first_found', dict(files=['test-ini.conf'], skip=true)) | ternary(lookup('ini', 'foo section=DEFAULT file=test-ini.conf'), omit) }}"

在这个例子中 first_found 查找返回文件名，如果文件存在，否则为空列表.如果文件存在，ternary 过滤器调用 ini 查找，否则返回 omit 占位符.

In this example first_found lookup return file name if file exists or empty list otherwise. If file exists, ternary filter calls ini lookup, otherwise omit placeholder is returned.

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