CloudFormation：创建资源（如果它们不存在），但不删除它们

我有以下CloudFormation模板 . （它默认基于在AWS Lambda中运行C＃Web API而创建的模板，但这可能不相关 . ）

它创建AWS Lambda函数 . 如果现有资源的名称未作为参数提供，则模板还会创建IAM角色和DynamoDB表 .

那部分有效 . 如果没有为角色和表提供名称，则会创建它们 .

The problem exists when I run the template a second time to perform updates: 此时，我的角色和表存在，所以我提供了名称作为参数 . 但是，当CloudFormation第二次运行时，它首次创建的资源（角色和表）将被删除 .

Is there some way to set up the template such that it will create new resources if they don't exist, but not delete them if they are already present?

我没有对CloudFormation做过很多，但我确实通过了文档 . 我找到的最接近的是setting a stack policy，但它似乎不是模板的一部分 . 看起来事后我必须在管理控制台中这样做 .

{
  "AWSTemplateFormatVersion" : "2010-09-09",
  "Transform" : "AWS::Serverless-2016-10-31",
  "Description" : "...",

  "Parameters" : {
    "ShouldCreateTable" : {
      "Type" : "String",        
      "AllowedValues" : ["true", "false"],
      "Description" : "If true then the underlying DynamoDB table will be created with the CloudFormation stack."
    },  
    "TableName" : {
        "Type" : "String",
        "Description" : "Name of DynamoDB table to be used for underlying data store. If left blank a new table will be created.",
        "MinLength" : "0"
    },
    "ShouldCreateRole" : {
      "Type" : "String",        
      "AllowedValues" : ["true", "false"],
      "Description" : "If true then the role for the Lambda function will be created with the CloudFormation stack."
    },  
    "RoleARN" : {
        "Type" : "String",
        "Description" : "ARN of the IAM Role used to run the Lambda function. If left blank a new role will be created.",
        "MinLength" : "0"
    }
  },

  "Conditions" : {
    "CreateDynamoTable" : {"Fn::Equals" : [{"Ref" : "ShouldCreateTable"}, "true"]},
    "TableNameGenerated" : {"Fn::Equals" : [{"Ref" : "TableName"}, ""]},
    "CreateRole":{"Fn::Equals" : [{"Ref" : "ShouldCreateRole"}, "true"]},
    "RoleGenerated" : {"Fn::Equals" : [{"Ref" : "RoleARN"}, ""]}
  },

  "Resources" : {

    "Get" : {
      "Type" : "AWS::Serverless::Function",
      "Properties": {
        ...
        "Role": {"Fn::If" : ["CreateRole", {"Fn::GetAtt":["LambdaRole", "Arn"]}, {"Ref":"RoleARN"}]},
        "Environment" : {
          "Variables" : {
            "AppDynamoTable" : { "Fn::If" : ["CreateDynamoTable", {"Ref":"DynamoTable"}, { "Ref" : "TableName" } ] }
          }
        },
        ...
      }
    },

    "LambdaRole":{
        "Type":"AWS::IAM::Role",
        "Condition":"CreateRole",
        "Properties":{
            "ManagedPolicyArns":["arn:aws:iam::aws:policy/AWSLambdaFullAccess"],
            "AssumeRolePolicyDocument": {
               "Version" : "2012-10-17",
               "Statement": [ {
                  "Effect": "Allow",
                  "Principal": {
                     "Service": [ "lambda.amazonaws.com" ]
                  },
                  "Action": [ "sts:AssumeRole" ]
               } ]
            },
            "Policies": [  {
                "PolicyName": "root",
                "PolicyDocument": {
                        "Version": "2012-10-17",
                        "Statement": [
                            {
                                "Effect": "Allow",
                                "Action": [
                                    "dynamodb:Query",
                                    "dynamodb:Scan",
                                    "dynamodb:PutItem",
                                    "dynamodb:GetItem",
                                    "dynamodb:UpdateItem",
                                    "dynamodb:DeleteItem",
                                    "logs:CreateLogGroup",
                                    "logs:CreateLogStream",
                                    "logs:PutLogEvents"
                                ],
                                "Resource": [
                                    "*"
                                ]
                            }
                        ]
                    }
                }
            ]
        }
    },

    "DynamoTable" : {
        "Type" : "AWS::DynamoDB::Table",
        "Condition" : "CreateDynamoTable",
        "Properties" : {
            "TableName" : { "Fn::If" : ["TableNameGenerated", {"Ref" : "AWS::NoValue" }, { "Ref" : "TableName" } ] },
            "AttributeDefinitions": [
                { "AttributeName" : "id", "AttributeType" : "S" }
            ],
            "KeySchema" : [
                { "AttributeName" : "id", "KeyType" : "HASH"}
            ],          
            "ProvisionedThroughput" : { "ReadCapacityUnits" : "5", "WriteCapacityUnits" : "5" }
        }
    }
  },

  "Outputs" : {
    "UnderlyingDynamoTable" : {
        "Value" : { "Fn::If" : ["CreateDynamoTable", {"Ref":"DynamoTable"}, { "Ref" : "TableName" } ] }
    },
    "LambdaRole" : {
        "Value" : {"Fn::If" : ["CreateRole", {"Fn::GetAtt":["LambdaRole", "Arn"]}, {"Ref":"RoleARN"} ] }
    }
  }
}

我可以删除创建步骤并在API网关之前手动创建资源，但似乎我应该尝试做的事情 .