CloudFormation栈创建失败：需指定两个不同可用区的子网

错误提示明确要求负载均衡器必须指定至少两个位于不同可用区的子网，当前你的模板存在两个关键问题：

1. 所有子网未显式指定可用区，AWS默认会将它们放置在同一个可用区
2. 负载均衡器LoadBalance仅关联了一个子网Subnet1

1. 定义跨可用区的子网 #

在子网资源的Properties中添加AvailabilityZone属性，指定不同的可用区。推荐使用AWS内置伪参数动态获取当前区域的可用区，避免硬编码：

• 给Subnet1添加：

  AvailabilityZone: !Select [0, !GetAZs '']
  

• 给Subnet2添加：

  AvailabilityZone: !Select [1, !GetAZs '']
  

!GetAZs ''会返回当前部署区域的所有可用区列表，!Select选取列表中第0和第1个可用区，确保两个子网处于不同可用区。

2. 给负载均衡器关联多个跨可用区子网 #

修改LoadBalance的Subnets属性，添加至少两个子网：

Subnets:
  - !Ref Subnet1
  - !Ref Subnet2

3. 修正模板中的其他错误 #

模板还有两处明显错误需要修正，否则即使解决子网问题，栈仍会创建失败：

• AppLBListnerS1的TargetGroupArn错误：当前指向!Ref VPC，应该关联一个AWS::ElasticLoadBalancingV2::TargetGroup资源，需先定义目标组再引用其ARN。
• EC2Net2资源缺失：错误提示中提到EC2Net2创建失败，但模板中仅存在EC2Net1，请确认是否遗漏了该资源定义。

修正后的完整模板示例 #

---
AWSTemplateFormatVersion: 2010-09-09

Parameters:
  DBName:
    Default: RBDB
    Description: 数据库名称
    Type: String
    MinLength: '1'
    MaxLength: '64'
    AllowedPattern: '[a-zA-Z][a-zA-Z0-9]*'

  DBUsername:
    Type: String
    Description: 数据库主用户名
    Default: admin

  DBPassword:
    Type: String
    NoEcho: true
    Description: 数据库主密码
    Default: password

  DBInstanceClass:
    Default: db.m5.large
    Description: 数据库实例类型
    Type: String

  DBAllocStore:
    Default: '500'
    Description: 数据库存储大小(GiB)
    Type: Number
    MinValue: '20'
    MaxValue: '65536'

  RBDBInstance:
    Default: RBDBInstance
    Description: 数据库实例标识符
    Type: String
    MinLength: '1'
    MaxLength: '80'
    AllowedPattern: '[a-zA-Z][a-zA-Z0-9]*'

Resources:
  VPC:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: 10.0.0.0/16
      EnableDnsSupport: true
      EnableDnsHostnames: true
      Tags:
      - Key: Name
        Value: VPC

  S3Bucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: 'aws--S3Bucket'

  IGateway:
    Type: AWS::EC2::InternetGateway
    Properties:
      Tags:
      - Key: Name
        Value: VPC Internet Gateway

  Subnet1:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      CidrBlock: 10.0.20.0/24
      AvailabilityZone: !Select [0, !GetAZs ''] # 新增：指定第一个可用区
      MapPublicIpOnLaunch: false
      Tags:
        - Key: Name
          Value: 'PrivateSubnet1'

  Subnet2:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      CidrBlock: 10.0.30.0/24
      AvailabilityZone: !Select [1, !GetAZs ''] # 新增：指定第二个可用区
      MapPublicIpOnLaunch: true
      Tags:
        - Key: Name
          Value: 'PublicSubnet2'

  SSHSecGrp:
    Type: AWS::EC2::SecurityGroup
    Properties:
      VpcId: !Ref VPC
      GroupDescription: Security group egress
      SecurityGroupEgress:
        - CidrIp: 127.0.0.111/32
          IpProtocol: "-1"
 
  EC2SecGrp:
    Type: AWS::EC2::SecurityGroup
    Properties:
      VpcId: !Ref VPC
      GroupDescription: EC2 Security Group
      GroupName: aws-security-grp
      SecurityGroupIngress:
      - IpProtocol: tcp
        FromPort: 80
        ToPort: 80

  EC2Net1:
    Type: AWS::EC2::Instance
    Properties:
      InstanceType: t2.micro
      ImageId: 'ami-05c13eab67c5d8861'
      SecurityGroupIds:
        - !Ref EC2SecGrp
      SubnetId: !Ref Subnet1
      KeyName: EC2Net1
      UserData: 
        Fn::Base64: !Sub |
          #!/bin/bash
          yum update -y
          yum install -y httpd
          systemctl start httpd
          systemctl enable httpd
          #echo "<h1>Hello from Region us-east-2b</h1>" > /var/www/html/index.html

  # 新增：定义目标组，供负载均衡器监听使用
  TargetGroup1:
    Type: AWS::ElasticLoadBalancingV2::TargetGroup
    Properties:
      VpcId: !Ref VPC
      Port: 80
      Protocol: HTTP
      TargetType: instance
      Targets:
        - Id: !Ref EC2Net1

  S3BuckPol:
    Type: 'AWS::S3::BucketPolicy'
    Properties:
      Bucket: !Ref S3Bucket
      PolicyDocument:
        Statement:
          - Effect: Allow
            Action: 's3:*'
            Resource: !Sub 'arn:aws:s3:::${S3Bucket}/*'
            Principal:
              AWS: !Sub 'arn:aws:iam::${AWS::AccountId}:user/@matthew'

  LoadBalance:
    Type: AWS::ElasticLoadBalancingV2::LoadBalancer
    Properties:
      Name: aws-elb-load-balance2
      Scheme: internet-facing
      Subnets:
      - !Ref Subnet1 # 保留第一个子网
      - !Ref Subnet2 # 新增：添加第二个跨可用区子网

  AppLBListnerS1:
    Type: AWS::ElasticLoadBalancingV2::Listener
    Properties:
      DefaultActions:
        - Type: forward
          TargetGroupArn: !Ref TargetGroup1 # 修改为引用目标组ARN
      LoadBalancerArn: !Ref LoadBalance
      Port: 80
      Protocol: HTTP

  MyRDS:
    Type: 'AWS::RDS::DBInstance'
    Properties:
      DBInstanceIdentifier: !Ref RBDBInstance
      DBName: !Ref DBName
      DBInstanceClass: !Ref DBInstanceClass
      AllocatedStorage: !Ref DBAllocStore
      Engine: MySQL
      MasterUsername: !Ref DBUsername
      MasterUserPassword: !Ref DBPassword

Outputs:
  EC2InstanceNet1:
    Value: !Ref EC2Net1

  S3BucketName:
    Value: !Ref S3Bucket

  DBInstanceId:
    Value: !Ref RBDBInstance

  LoadBalancerDNS:
    Value: !GetAtt LoadBalance.DNSName

内容的提问来源于stack exchange，提问作者Data Science Analytics Manager