Amazon cloudformation CloudFormation中的属性DeviceIndex不能为空

我对云的形成非常陌生，并试图掌握它。作为学习过程的一部分，我正在尝试构建一个模板，用于创建一个VPC、一个子网和部署一个面向公众的实例。下面是我在CF设计窗口中完成的代码。虽然我的代码只在构建时进行验证，但我得到的错误如下-

CREATE_FAILED   AWS::EC2::Instance  AR3Web  Property DeviceIndex cannot be empty.
ROLLBACK_IN_PROGRESS    AWS::CloudFormation::Stack  Intro   The following resource(s) failed to create:[IgwAttachment, AR3Web]. . Rollback requested by user. 

我正在代码中设置DeviceIndex:“0”。有人能帮我理解我哪里出了问题吗

提前谢谢你的帮助

我的代码-

---
AWSTemplateFormatVersion: 2010-09-09
Description: Test Stack
Resources:
  AR3VPC:
    Type: 'AWS::EC2::VPC'
    Properties:
      CidrBlock: 10.0.0.0/16
      EnableDnsSupport: 'true'
      EnableDnsHostnames: 'true'
      InstanceTenancy: default
      Tags:
        - Key: Name
          Value: AR3VPC
    Metadata:
      'AWS::CloudFormation::Designer':
        id: baa1b4d4-07ea-4095-b4a4-4925e7c68052
  PublicSubnet1:
    Type: 'AWS::EC2::Subnet'
    Properties:
      VpcId: !Ref AR3VPC
      CidrBlock: 10.0.1.0/24
      MapPublicIpOnLaunch: 'true'
      AvailabilityZone: us-east-1a
    Metadata:
      'AWS::CloudFormation::Designer':
        id: 24f10588-e12e-45bf-a270-c844afa4d9a7
  AR3Web:
    Type: 'AWS::EC2::Instance'
    Properties:
      ImageId: 'ami-a4c7edb2'
      InstanceType: 't2.micro'
      KeyName: virginiakp
      NetworkInterfaces:
        - GroupSet:
            - !Ref AR3WebSG
          AssociatePublicIpAddress: 'true'
          DeviceIndex: '0'
          DeleteOnTermination: 'true'
        - SubnetId: !Ref PublicSubnet1
    Metadata:
      'AWS::CloudFormation::Designer':
        id: 6080a1d9-2670-48db-abf8-a7a3ac597f2e
  AR3WebSG:
    Type: 'AWS::EC2::SecurityGroup'
    Properties:
      GroupDescription: Allow HTTP access
      SecurityGroupIngress:
        - IpProtocol: tcp
          FromPort: 80
          ToPort: 80
          CidrIp: 0.0.0.0/0
      VpcId: !Ref AR3VPC
      Tags:
        - Key: Name
          Value: AR3WebSecurityGroup
    Metadata:
      'AWS::CloudFormation::Designer':
        id: 2870d531-f538-4bee-8a03-393012432b71
  AR3IGW:
    Type: 'AWS::EC2::InternetGateway'
    Properties:
      Tags:
        - Key: Name
          Value: AR3 IGW
    Metadata:
      'AWS::CloudFormation::Designer':
        id: c2557116-9cd5-4826-9932-656e90b271a1
  AR3Rt:
    Type: 'AWS::EC2::RouteTable'
    Properties:
      VpcId: !Ref AR3VPC
    Metadata:
      'AWS::CloudFormation::Designer':
        id: e9f2dfcc-e65b-49c5-8a21-66dd3b012549
  PubRt:
    Type: 'AWS::EC2::Route'
    DependsOn: IgwAttachment
    Properties:
      RouteTableId: !Ref AR3Rt
      DestinationCidrBlock: 0.0.0.0/0
      GatewayId: !Ref AR3IGW
    Metadata:
      'AWS::CloudFormation::Designer':
        id: 37bac7d1-69ee-4c1c-9a8d-8940e586b590
  IgwAttachment:
    Type: 'AWS::EC2::VPCGatewayAttachment'
    Properties:
      InternetGatewayId: !Ref AR3IGW
      VpcId: !Ref AR3VPC
    Metadata:
      'AWS::CloudFormation::Designer':
        id: 72d68293-8163-4372-a771-1f4a4062d6dd
  PublicSubnetRouteTableAssociation:
    Type: 'AWS::EC2::SubnetRouteTableAssociation'
    Properties:
      SubnetId: !Ref PublicSubnet1
      RouteTableId: !Ref AR3Rt
    Metadata:
      'AWS::CloudFormation::Designer':
        id: 7e429e8b-2fb5-49de-a383-60ec910ed505

---

您看到该消息是因为您的网络接口数组中有一个输入错误。你有：

NetworkInterfaces:
  - GroupSet:
      - !Ref AR3WebSG
    AssociatePublicIpAddress: 'true'
    DeviceIndex: '0'
    DeleteOnTermination: 'true'
  - SubnetId: !Ref PublicSubnet1

SubnetId旁边的连字符似乎是一个输入错误，但在YAML中，它表示网络接口数组中的一个新元素。因此，虽然第一个元素有DeviceIndex:0，但第二个元素没有DeviceIndex，这就是您接收该消息的原因

将其更改为：

NetworkInterfaces:
  - GroupSet:
      - !Ref AR3WebSG
    AssociatePublicIpAddress: 'true'
    DeviceIndex: '0'
    DeleteOnTermination: 'true'
    SubnetId: !Ref PublicSubnet1

---

非常感谢，亚历克斯。你真有一双锐利的眼睛！这解决了问题，堆栈成功完成！