Conditions类型于编程语言中的if/else逻辑，
下面的模板中有一个EnvType参数，当CloudFormation检测到它的值为prod时，额外增加一块磁盘，当标签为test时，仅挂一块磁盘。
当EnvType = prod时，CreateProdResources的值为true
而NewVolume和MountPoint资源和CreateProdResources条件做了关联，仅当满足条件时才创建这两个资源：
AWSTemplateFormatVersion: "2010-09-09"
Mappings:
RegionMap:
us-east-1:
AMI: "ami-0ff8a91507f77f867"
TestAz: "us-east-1a"
us-west-1:
AMI: "ami-0bdb828fd58c52235"
TestAz: "us-west-1a"
us-west-2:
AMI: "ami-a0cfeed8"
TestAz: "us-west-2a"
Parameters:
EnvType:
Description: Environment type.
Default: test
Type: String
AllowedValues:
- prod
- test
ConstraintDescription: must specify prod or test.
Conditions:
CreateProdResources: !Equals [ !Ref EnvType, prod ]
Resources:
EC2Instance:
Type: "AWS::EC2::Instance"
Properties:
ImageId: !FindInMap [RegionMap, !Ref "AWS::Region", AMI]
MountPoint:
Type: "AWS::EC2::VolumeAttachment"
Condition: CreateProdResources
Properties:
InstanceId:
!Ref EC2Instance
VolumeId:
!Ref NewVolume
Device: /dev/sdh
NewVolume:
Type: "AWS::EC2::Volume"
Condition: CreateProdResources
Properties:
Size: 100
AvailabilityZone:
!GetAtt EC2Instance.AvailabilityZone
Outputs:
VolumeId:
Condition: CreateProdResources
Value:
!Ref NewVolume