使 VPC 创建成为可选项

Question

我试图在我的 cloudformation 脚本中使 VPC 创建有条件。比如参数中提供了一个VPC id，那么我要创建这个VPC中的所有资源，否则就新建一个。

当我想重用现有的 VPC 时，问题就出现了，但我无法推断出我的资源之一需要的子网。所以我想，我必须提供它们作为参数。但是如果我将它们作为参数提供，在我想创建一个新 VPC 的情况下，它会抱怨，因为子网 ID 列表是空的，而且它必须是有效的。

错误是Parameter validation failed: parameter value for parameter name VpcPrivateSubnetIds does not exist. Rollback requested by user.不可能给出任何虚拟值。有什么想法可以实现吗？

这是我的 CF 脚本：

VpcId:
  Type: String
  Description: Give the VPC id if you want to use an existing one. Leave empty for creating a new one.

VpcPublicSubnetIds:
  Type: List<AWS::EC2::Subnet::Id>
  Description: List of 3 public SubnetIds for the given VPC. 

VpcPrivateSubnetIds:
  Type: List<AWS::EC2::Subnet::Id>
  Description: List of 3 private SubnetIds for the given VPC. 


Conditions:
  CreateVPC: !Equals [ !Ref VpcId, ""]


Resources: 
  (...)
    Properties:
      PrivateSubnetIds: !If
        - CreateVPC
        - !GetAtt VPCStack.Outputs.PrivateSubnets
        - !Join [',', [!Select [0, !Ref VpcPrivateSubnetIds], !Select [1, !Ref VpcPrivateSubnetIds], !Select [2, !Ref VpcPrivateSubnetIds]]]
      PublicSubnetIds: !If
        - CreateVPC
        - !GetAtt VPCStack.Outputs.PublicSubnets
        - !Join [',', [!Select [0, !Ref VpcPublicSubnetIds], !Select [1, !Ref VpcPublicSubnetIds], !Select [2, !Ref VpcPublicSubnetIds]]]

Answer 1

一种解决方案是将 subnetId 参数视为字符串，然后将其保留为空。（但是当存在 VPC 时，用户必须手动输入子网 ID 列表）。

如果列表不为空（要使用现有 VPC），请使用 Cloudformation custom resource lambda 将字符串（逗号分隔）转换为列表 & return 到 cloudformation 以用于资源创建。所以你的堆栈看起来像

Parameters:
  VpcId:
    Type: String
    Description: Give the VPC id if you want to use an existing one. Leave empty for creating a new one.
  VpcPublicSubnetIds:
    Type: String
    Description: List of 3 public SubnetIds for the given VPC.
    Default: ''
  VpcPrivateSubnetIds:
    Type: String
    Description: List of 3 private SubnetIds for the given VPC.
    Default: ''
Conditions:
  CreateVPC: !Equals [ !Ref VpcId, ""]
  CreateList: !Not [!Equals [ !Ref VpcId, ""]]
Resources:
  CreateList:
    Type: AWS::CloudFormation::CustomResource
    Condition: CreateList
    Properties:
      ServiceToken:<some token>
      Public: !Ref VpcPublicSubnetIds
      Private: !Ref VpcPrivateSubnetIds
  SomeResource:
    Properties:
      PrivateSubnetIds: !If
        - CreateVPC
        - !GetAtt VPCStack.Outputs.PrivateSubnets
        - !GetAtt CreateList.PrivateSubnetIds
      PublicSubnetIds: !If
        - CreateVPC
        - !GetAtt VPCStack.Outputs.PublicSubnets
        - !GetAtt CreateList.PublicSubnetIds

请注意我已验证此脚本，因此您可能需要进行一些更正。

使 VPC 创建成为可选项

Make VPC creation optional

amazon-web-services

amazon-cloudformation

amazon-vpc