Ansible 解析布尔变量的准确程度如何? [英] How Exactly Does Ansible Parse Boolean Variables?

问题描述

在 Ansible 中，有几个地方可以定义变量:在清单中、在剧本中、在变量文件中等等.谁能解释一下我所做的以下观察?

1. 在清单中定义布尔变量时，它必须大写(即 True/False)，否则(即 true/false)它不会被解释为布尔值，而是解释为字符串.
2. 在任何 YAML 格式的文件(剧本、角色等)中，真/假和真/假都被解释为布尔值.

例如，我在一个清单中定义了两个变量:

abc=falsexyz=假

并且在调试角色内部这些变量的类型时...

- 调试:msg: "abc={{ abc | type_debug }} xyz={{ xyz | type_debug }}"

... 然后 abc 变成 unicode 但 xyz 被解释为 bool:

ok: [localhost] =>{"msg": "abc=unicode xyz=bool"}

但是，在剧本中定义相同的变量时，如下所示:

 变量:abc:假xyz:错误

... 那么这两个变量都被识别为 bool.

在生产中执行剧本后，我不得不以艰难的方式意识到这一点，运行一些不应该运行的东西，因为库存中的变量设置为false"而不是False".因此，我真的很想找到关于 Ansible 如何理解布尔值以及它如何取决于变量的定义位置/方式的明确答案.为了安全起见，我应该总是使用大写的 True/False 吗?可以说 YAML 文件中的布尔值(格式为 key: value)不区分大小写，而在属性文件中(格式为 key=value)它们是大小写的吗?-敏感的?任何更深入的见解将不胜感激.

解决方案

YAML 文件中定义的变量(剧本、vars_files、YAML 格式的清单)

---

YAML 原则

Playbooks、vars_files 和 用 YAML 编写的清单文件首先由 YAML 解析器处理.它允许将值存储为 Boolean 类型的多个别名:yes/no, true/false、on/off，定义在几种情况下:true/True/TRUE(因此它们并非真正不区分大小写).

YAML 定义 将可能的值指定为:

<块引用>

y|Y|yes|Yes|YES|n|N|no|No|NO|真|真|真|假|假|假|开|开|开|关|关|关

Ansible 文档确认:

<块引用>

您还可以以多种形式指定布尔值(真/假):

create_key: 是需要代理:没有know_oop: 真likes_emacs:真uses_cvs: 假

---

---

INI 格式清单文件中定义的变量

---

Python 原理

当 Ansible 读取 INI 格式的清单时，它会处理变量 使用 Python 内置类型:

<块引用>

使用 key=value 语法传入的值被解释为 Python 文字结构(字符串、数字、元组、列表、字典、布尔值、无)，或者作为字符串.例如 var=FALSE 将创建一个等于 FALSE 的字符串.

如果指定的值与字符串 True 或 False(以大写字母开头)匹配，则类型设置为布尔值，否则将其视为字符串(除非匹配另一种类型).

---

---

通过--extra_vars CLI 参数定义的变量

---

所有字符串

在 CLI 中作为 extra-vars 传递的所有变量都是字符串类型.

In Ansible, there are several places where variables can be defined: in the inventory, in a playbook, in variable files, etc. Can anyone explain the following observations that I have made?

1. When defining a Boolean variable in an inventory, it MUST be capitalized (i.e., True/False), otherwise (i.e., true/false) it will not be interpreted as a Boolean but as a String.
2. In any of the YAML formatted files (playbooks, roles, etc.) both True/False and true/false are interpreted as Booleans.

For example, I defined two variables in an inventory:

abc=false
xyz=False

And when debugging the type of these variables inside a role...

- debug:
    msg: "abc={{ abc | type_debug }}  xyz={{ xyz | type_debug }}"

... then abc becomes unicode but xyz is interpreted as a bool:

ok: [localhost] => {
    "msg": "abc=unicode  xyz=bool"
}

However, when defining the same variables in a playbook, like this:

  vars:
    abc: false
    xyz: False

... then both variables are recognized as bool.

I had to realize this the hard way after executing a playbook on production, running something that should not have run because of a variable set to 'false' instead of 'False' in an inventory. Thus, I'd really like to find a clear answer about how Ansible understands Booleans and how it depends on where/how the variable is defined. Should I simply always use capitalized True/False to be on the safe side? Is it valid to say that booleans in YAML files (with format key: value) are case-insensitive, while in properties files (with format key=value) they are case-sensitive? Any deeper insights would be highly appreciated.

解决方案

Variables defined in YAML files (playbooks, vars_files, YAML-format inventories)

---

YAML principles

Playbooks, vars_files, and inventory files written in YAML are processed by a YAML parser first. It allows several aliases for values which will be stored as Boolean type: yes/no, true/false, on/off, defined in several cases: true/True/TRUE (thus they are not truly case-insensitive).

YAML definition specifies possible values as:

y|Y|yes|Yes|YES|n|N|no|No|NO
|true|True|TRUE|false|False|FALSE
|on|On|ON|off|Off|OFF

Ansible docs confirm that:

You can also specify a boolean value (true/false) in several forms:

create_key: yes
needs_agent: no
knows_oop: True
likes_emacs: TRUE
uses_cvs: false

---

---

Variables defined in INI-format inventory files

---

Python principles

When Ansible reads an INI-format inventory, it processes the variables using Python built-in types:

Values passed in using the key=value syntax are interpreted as Python literal structure (strings, numbers, tuples, lists, dicts, booleans, None), alternatively as string. For example var=FALSE would create a string equal to FALSE.

If the value specified matches string True or False (starting with a capital letter) the type is set to Boolean, otherwise it is treated as string (unless it matches another type).

---

---

Variables defined through --extra_vars CLI parameter

---

All strings

All variables passed as extra-vars in CLI are of string type.

这篇关于Ansible 解析布尔变量的准确程度如何?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！