如何在！Sub中使用！FindInMap |用户数据部分 [英] How to use !FindInMap in !Sub | userdata section

问题描述

目前，我正在将CFT从JSON转换为Yaml。一切正常，直到Userdata部分。我很难使用userdata部分中的！Ref或！FindInMap之类的功能。

Currently I am converting CFT from JSON to Yaml. Everything works fine until Userdata section.I am having hard time to use any of functions like !Ref or !FindInMap in userdata section.

UserData：

Fn::Base64: !Sub |
        #!/bin/bash -v
        /command {Fn::FindInMap: [ "url", Ref: AWS::Region, Ref: EnvironmentType ] } 

如果有人可以共享任何代码段，这将非常有帮助。

It would be very helpful, If anyone can share any snippet of code.

推荐答案

与此同时，我也一直在玩游戏。尽管文档表示<$ Fn :: Sub 支持c $ c> Fn :: FindInMap ，没有使用示例，我尝试了各种组合引号和冒号都没有成功，但是我似乎终于找到了使用映射的功能解决方案。以下应该可以工作：

I've been having fun and games with this as well. Although the documentation says that Fn::FindInMap is supported in Fn::Sub, there's no example of use and I've tried all sorts of combinations of quotes and colons without success, but I finally seem to have hit upon a functional solution using mappings. The following should work:

Fn::Base64: !Sub
  - |+
    #!/bin/bash -v
    /command ${Url}
  - Url:
      Fn::FindInMap:
        - UrlMap
        - !Ref AWS::Region
        - !Ref EnvironmentType

arg0开头的管道告诉YAML保留换行符，并且加号告诉它以后要保留换行符。
Arg1告诉它用 Fn :: FindInMap 的结果替换arg0中的Url。

The pipe at the start of arg0 tells YAML to preserve newlines, and the plus tells it to keep a newline afterwards. Arg1 tells it to substitute the result of the Fn::FindInMap for the Url in arg0.

以下较短的版本也应该起作用：

The following shorter version should also work:

Fn::Base64: !Sub
  - |+
    #!/bin/bash -v
    /command ${Url}
  - Url:
      Fn::FindInMap: [UrlMap, Ref: "AWS::Region", Ref: EnvironmentType]

但是您应该测试一下。请注意逗号，引号和还原为 Ref： s而不是！Ref s。这可能告诉我们一些有关文件如何进行预处理的信息，但是我不确定那是什么。

But you should test that. Note the commas, quotes, and reversion to Ref:s rather than !Refs. This probably tells us something about how the files are being pre-processed, but I'm not sure what that is.

我确信此解决方案对于经验丰富的YAML专家，但是当所有这些YAMLy优势添加到CloudFormation中时，我才刚刚开始了解JSON。

I'm sure that this solution is obvious to experienced YAMLers, but I was only just starting to get my head around JSON when all this YAMLy goodness was added to CloudFormation.

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