仅当实体尚不存在时，我才能在 CloudFormation 中设置属性吗？

如何解决仅当实体尚不存在时，我才能在 CloudFormation 中设置属性吗？

我通过 Amplify 有一个 CloudFormation，它定义了一个 Cognito 用户池。我想将从此模板部署的未来环境设置为具有 UsernameConfiguration.CaseSensitive: False。如果我只是将该属性添加到我的 CloudFormation 模板，更新将失败并显示以下错误：

Reason: Updates are not allowed for property - UsernameConfiguration. (Service: AWSCognitoIdentityProvider; Status Code: 400; Error Code: InvalidParameterException; Request ID: null; Proxy: null)

有没有办法根据池是否已经存在来调节这个属性？我希望创建的任何新环境都使用新配置，但仍允许部署旧环境。

这是 Amplify 用来创建用户池的 CloudFormation 模板的片段。

    # BEGIN USER POOL RESOURCES
    UserPool:
        # Created upon user selection
        # Depends on SNS Role for Arn if MFA is enabled
        Type: AWS::Cognito::UserPool
        UpdateReplacePolicy: Retain
        Properties:
            UserPoolName:
                !If [
                    ShouldNotCreateEnvResources,!Ref userPoolName,!Join ["",[!Ref userPoolName,"-",!Ref env]],]

            Schema:
                - Name: email
                  required: true
                  Mutable: true

            LambdaConfig:
                PostAuthentication: !Ref functiontestcd9b6b5ePostAuthenticationArn

                PostConfirmation: !Ref functiontestcd9b6b5ePostConfirmationArn

                PretokenGeneration: !Ref functiontestcd9b6b5ePretokenGenerationArn

            AutoVerifiedAttributes: !Ref autoVerifiedAttributes

            EmailVerificationMessage: !Ref emailVerificationMessage
            EmailVerificationSubject: !Ref emailVerificationSubject

            Policies:
                PasswordPolicy:
                    MinimumLength: !Ref passwordPolicyMinLength
                    RequireLowercase: false
                    RequireNumbers: false
                    RequireSymbols: false
                    RequireUppercase: false

            UsernameAttributes: !Ref usernameAttributes

            MfaConfiguration: !Ref mfaConfiguration
            SmsverificationMessage: !Ref smsverificationMessage
            SmsAuthenticationMessage: !Ref smsAuthenticationMessage
            SmsConfiguration:
                SnsCallerArn: !GetAtt SNSRole.Arn
                ExternalId: testcd9b6b5e_role_external_id
            UsernameConfiguration:
                CaseSensitive: False

解决方法

有没有办法根据池是否已经存在来调节这个属性？

遗憾的是它不可能，因为 CFN 没有检查池是否存在的功能。如果您需要此类功能，则必须使用 custom resource 自行实现。