AWS Cloudformation 将条件函数解释为资源 属性

Question

我在使用 cloudformation 模板时遇到了一个奇怪的行为。这是我的模板，我在其中创建了一个存储桶并希望根据条件进行通知配置：

AWSTemplateFormatVersion: '2010-09-09'
Description: "Setup Artifacts Bucket"
Parameters:
  BucketName:
    Description: Name of the pipeline setup arctifact bucket
    Type: String 
    Default: "s3-pipeline-setup"
  NotificationCondition:
    Description: Conditionally add Notification configuration to the artifact bucket
    Type: String
    Default: false
Conditions:
  AddNotificationConfiguration: !Equals [ !Ref NotificationCondition, true ]

Resources:
  ArtifactBucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: !Ref BucketName
      Fn::If:
        - AddNotificationConfiguration
        -
          NotificationConfiguration:
            LambdaConfigurations:
              -
                Function: "arn:aws:lambda:eu-west-1:341292222222227:function:lambda-ops-trigger-pipeline-setup"
                Event: "s3:ObjectCreated:*"
                Filter:
                  S3Key:
                    Rules:
                      -
                        Name: prefix
                        Value: "appstackcodes/"
                      -
                        Name: suffix
                        Value: "txt"
        - !Ref AWS::NoValue

当我尝试部署时失败并出现此错误：

00:28:10 UTC+0200 CREATE_FAILED AWS::S3::Bucket ArtifactBucket Encountered unsupported property Fn::If

我不太明白这件事..有人可以试试让我知道那里的错误吗？

谢谢

Answer 1

不幸的是，您无法在 cloudformation 中执行您想要的操作。

Fn::If 基本上可以用作三元表达式。例如

key: Fn::If: [condition_name, value_if_true, value_if_false]

它不能像在编程语言中那样用作逻辑流。有很多方法可以解决。您实际上似乎已经发现了 AWS::NoValue，所以只需将 NotificationConfiguration 赋值移动到 if.

之外即可

Resources:
  ArtifactBucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: !Ref BucketName
      NotificationConfiguration:
        Fn::If:
          - AddNotificationConfiguration
          - LambdaConfigurations:
              -
                Function: "arn:aws:lambda:eu-west-1:341294322147:function:lambda-itops-trigger-pipeline-setup"
                Event: "s3:ObjectCreated:*"
                Filter:
                  S3Key:
                    Rules:
                      -
                        Name: prefix
                        Value: "appstackcodes/"
                      -
                        Name: suffix
                        Value: "txt"
          - !Ref AWS::NoValue

实际上，您总是在为 NotificationConfiguration 分配一些内容，但有时这很神奇 AWS::NoValue。这在大多数情况下都有效，尽管有时这还不够，需要更多的创造力！