syntax of the Conditions section of a template - Resource Orchestration Service

You can use Fn::And, Fn::Or, Fn::Not, or Fn::Equals to define a condition statement. In each condition, you can reference another condition, a parameter value, or a mapping. You can associate conditions with resources in the Resources and Outputs sections of a template. To associate conditions with resources, you can use the Fn::If function or the Condition property of the resources.

Syntax

The declaration of a condition consists of a condition name and a condition statement. The condition name is of the String type. You can use the following functions to define condition statements. You can reference other conditions in a condition. Each condition name must be unique.

You can use the following functions to define conditions, but cannot use the functions as the outermost functions:

"Fn::Select", "Fn::Join", "Fn::Split", "Fn::Replace", "Fn::Base64Encode", "Fn::Base64Decode", "Fn::MemberListToMap", "Fn::If", "Fn::ListMerge", "Fn::GetJsonValue", "Fn::MergeMapToList", "Fn::SelectMapList", "Fn::Add", "Fn::Avg", "Fn::Str", "Fn::Calculate", "Ref"(only for parameter references), and "Fn::FindInMap".

Examples

The following example shows how to define conditions:

Conditions:
  DevEnv:
    Fn::Equals:
      - Dev
      - Ref: EnvType
  UTEnv:
    Fn::Equals:
      - UT
      - Ref: EnvType
  PREEnv:
    Fn::Not:
      Fn::Or:
        - DevEnv
        - UTEnv
  ProdEnv:
    Fn::And:
      - Fn::Equals:
          - Prod
          - Ref: EnvType
      - PREEnv

The following example shows how to associate conditions with resources.

In this example, the EnvType value is used as a condition to determine whether to create a data disk and an Object Storage Service (OSS) bucket for an Elastic Compute Service (ECS) instance.

ROSTemplateFormatVersion: '2015-09-01'
Parameters:
  EnvType:
    Default: pre
    Type: String
Conditions:
  CreateProdRes:
    Fn::Equals:
      - prod
      - Ref: EnvType
Resources:
  WebServer:
    Type: ALIYUN::ECS::Instance
    Properties:
      DiskMappings:
        Fn::If:
          - CreateProdRes
          - - Category: cloud_efficiency
              DiskName: FirstDataDiskName
              Size: 40
            - Category: cloud_ssd
              DiskName: SecondDataDiskName
              Size: 40
          - Ref: ALIYUN::NoValue
      VpcId: vpc-2zew9pxh2yirtzqxd****
      SystemDiskCategory: cloud_efficiency
      SecurityGroupId: sg-2zece6wcqriejf1v****
      SystemDiskSize: 40
      ImageId: centos_6_8_64_40G_base_2017****.vhd
      IoOptimized: optimized
      VSwitchId: vsw-2zed9txvy7h2srqo6****
      InstanceType: ecs.n1.medium
  OssBucket:
    Type: ALIYUN::OSS::Bucket
    Condition: CreateProdRes
    Properties:
      AccessControl: private
      BucketName: myprodbucket
Outputs:
  InstanceId:
    Value:
      Fn::GetAtt:
        - WebServer
        - InstanceId
  OssDomain:
    Condition: CreateProdRes
    Value:
      Fn::GetAtt:
        - OssBucket
        - DomainName