Resource Orchestration Service:Resources

Property values can be text strings, string lists, booleans, referenced parameters, or return values of functions. When you create a JSON template, you must take note of the following rules for property values:

• Text strings must be enclosed in double quotation marks (").

• String lists must be enclosed in brackets ([ ]).

• Referenced parameters or return values of built-in functions must be enclosed in braces ({ }).

The preceding rules also apply when you combine text strings, string lists, referenced parameters, and return values of functions as property values. The following sample code provides an example on how to declare different types of property values:

{
  "Properties": {
    "String": "string",
    "LiteralList": [
      "value1",
      "value2"
    ],
    "Boolean": true,
    "ReferenceForOneValue": {
      "Ref": "ResourceID"
    },
    "FunctionResultWithFunctionParams": {
      "Fn::Join": [
        "%",
        [
          "Key=",
          {
            "Ref": "SomeParameter"
          }
        ]
      ]
    }
  }
}

When you delete a resource from a stack, one of the following situations may occur:

• If you set the DeletionPolicy property of a resource to Delete, the system deletes the resource when you delete the stack.

• If you set the DeletionPolicy property of a resource to Retain, the system retains the resource when you delete the stack.

The following sample code provides an example on how to declare the DeletionPolicy property to retain an ECS instance when the stack that contains the instance is deleted:

Resources:
  ECSInstance:
    Type: ALIYUN::ECS::Instance
    Properties:
      ImageId: m-25l0r****
    DeletionPolicy: Retain

The following sample code provides examples on how to configure dependencies.

• Configure a single dependency:

  DependsOn: ResourceName

• Configure multiple dependencies:

  DependsOn:
    - ResourceName1
    - ResourceName2

The following sample code provides an example on how to specify the DependsOn property. In this example, WebServer is created only after DatabaseServer is created.

ROSTemplateFormatVersion: '2015-09-01'
Resources:
  WebServer:
    Type: ALIYUN::ECS::Instance
    DependsOn: DatabseServer
  DatabseServer:
    Type: ALIYUN::ECS::Instance
    Properties:
      ImageId: m-25l0r****
      InstanceType: ecs.t1.small

The following sample code provides an example on how to specify the Condition property. In this example, whether WebServer is created is determined based on the value of MaxAmount.

ROSTemplateFormatVersion: '2015-09-01'
Parameters:
  MaxAmount:
    Type: Number
    Default: 1
Conditions:
  CreateWebServer:
    Fn::Not:
      Fn::Equals:
        - 0
        - Ref: MaxAmount
Resources:
  WebServer:
    Type: ALIYUN::ECS::InstanceGroup
    Condition: CreateWebServer
    Properties:
      ImageId: m-25l0rc****
      InstanceType: ecs.t1.small
      MaxAmount:
        Ref: MaxAmount
  DatabseServer:
    Type: ALIYUN::ECS::Instance
    Properties:
      ImageId: m-25l0r****
      InstanceType: ecs.t1.small

You can specify the Count property for a resource in a template to process the template and replace the resource with multiplied resources. ROS uses the processed template to manage stacks.

• For example, you set the Count property of Resource A to 3 in the original template. After ROS processes the template, Resource A is replaced with the following multiplied resources: Resources A[0], A[1], and A[2]. The following sample code provides an example of the original template:

  Resources:
    A:
      Count: 3
      ...

  The following sample code provides an example of the processed template:

  Resources:
    A[0]:
      ...
    A[1]:
      ...
    A[2]:
      ...

  Important

  If the name of a multiplied resource, such as A[1], is the same as the name of an existing resource that is defined in the original template, the template fails to be processed and validated.

  If you specify the Count property for a resource, the resource name is changed. We recommend that you do not specify the Count property for existing resources to prevent the resources from being deleted.

• The value of the Count property must be a natural number. The property supports only the following functions:

  • Ref (only for parameter references)

  • Fn::FindInMap

  • Fn::Select

  • Fn::Join

  • Fn::Split

  • Fn::Replace

  • Fn::Str

  • Fn::Base64Decode

  • Fn::If

  • Fn::ListMerge

  • Fn::GetJsonValue

  • Fn::MergeMapToList

  • Fn::SelectMapList

  • Fn::Add

  • Fn::Avg

  • Fn::Str

  • Fn::Calculate

  • Fn::Max

  • Fn::Min

  • Fn::Jq

  • Fn::Length

  • Fn::GetAZs

  • Fn::Index

  • Fn::FormatTime

  • Fn::MarketplaceImage

• A processed template can contain up to 300 resources.

• You can specify the ALIYUN::Index pseudo function in Properties of a resource for which the Count property is specified. When the system processes the template, the system replaces ALIYUN::Index with the values that correspond to multiplied resources. For example, the system replaces ALIYUN::Index for A[0] with 0 and replaces ALIYUN::Index for A[1] with 1. You can use ALIYUN::Index only in Properties of a resource for which the Count property is specified.

• If you specify the Count property for a resource and specify the resource in the DependsOn property, the resource is replaced with multiplied resources. The following sample code provides an example of the original template:

  DependsOn: A

  The following sample code provides an example of the processed template:

  DependsOn:
    - A[0]
    - A[1]
    - A[2]

• If you specify the Count property for a resource and specify the resource in Ref and Fn::GetAtt functions, the resource is replaced with multiplied resources. The following sample code provides an example of the original template:

  Ref: A
  Fn::GetAtt:
    - A
    - PropertyName

  The following sample code provides an example of the processed template:

  - Ref: A[0]
  - Ref: A[1]
  - Ref: A[2]
  - Fn::GetAtt:
      - A[0]
      - PropertyName
  - Fn::GetAtt:
      - A[1]
      - PropertyName
  - Fn::GetAtt:
      - A[2]
      - PropertyName

  If you specify the Count property for multiple resources and the resources are referenced by each other, we recommend that you use the Count property together with Fn::Select and ALIYUN::Index functions.

  Fn::Select:
    - Ref: ALIYUN::Index
    - Ref: A

  In this example, Resource A is used. You reference Resource A in Resource B and set the Count property of Resource B to 2. The following sample code provides an example on a part of the expressions of Resources B[0] and B[1] after the template is processed:

  - Ref: A[0]
  - Ref: A[1]

• If you specify the Count property for a resource, the DependsOn property also supports expressions. The functions that are supported by the expressions of the DependsOn property are the same as the functions that are supported by the expressions of the Count property. Both properties support the ALIYUN::Index pseudo parameter. The following table describes the formats and the calculation results of the expressions.

  Format	Example	Calculation result
  Dictionary	Fn::Split: - ',' - Server1,Server2	null. If the calculation result is null, the system removes the DependsOn property.
  		A string. If the calculation result is an empty string, the system removes the DependsOn property. If the calculation result is not an empty string, the calculation result must be a valid resource name.
  		A list. If the items in the list are null or empty strings, the system removes the items. If the list is empty, the system removes the DependsOn property. If the list is not empty, each item in the list must be a string and a valid resource name.
  List	- Server0 - Fn::Split: - ',' - Server1,Server2	The items in a list can be dictionaries or strings. Calculation results vary based on the item types. The following information describes the differences: If the items are dictionaries, the system calculates the expressions and returns the following calculation results: If the items are null or empty strings, the system removes the items. If the items are not null or empty strings, the items must be strings and valid resource names. If the items are strings, the items must be valid resource names. Note If the list is empty, the system removes the DependsOn property.
  String	Server0	A string. The system does not process a string.

  The following template shows how to specify Count to control the number of resources that can be created, and specify ParallelCount to control the maximum number of resources that can be created at a time:

  ROSTemplateFormatVersion: '2015-09-01'
  Parameters:
    Count:
      Type: Number
    ParallelCount:
      Type: Number
  Resources:
    WaitConditionHandle:
      Type: ALIYUN::ROS::WaitConditionHandle
      Count:
        Ref: Count
      DependsOn:
        Fn::Select:
          - Fn::Calculate:
              - 1-{0}//{1}
              - 0
              - - Fn::Min:
                    - Ref: ALIYUN::Index
                    - Ref: ParallelCount
                - Ref: ParallelCount
          - - Fn::Replace:
                - index:
                    Fn::Calculate:
                      - '{0}-{1}'
                      - 0
                      - - Ref: ALIYUN::Index
                        - Ref: ParallelCount
                - WaitConditionHandle[index]

  The processed templates that the system generates vary based on the values that you specify for Count and ParallelCount.

  • If you set Count to 3 and ParallelCount to 1, the system generates the following processed template:

    ROSTemplateFormatVersion: '2015-09-01'
    Resources:
      WaitConditionHandle[0]:
        Type: ALIYUN::ROS::WaitConditionHandle
      WaitConditionHandle[1]:
        Type: ALIYUN::ROS::WaitConditionHandle
        DependsOn: WaitConditionHandle[0]
      WaitConditionHandle[2]:
        Type: ALIYUN::ROS::WaitConditionHandle
        DependsOn: WaitConditionHandle[1]
    Parameters:
      Count:
        Type: Number
      ParallelCount:
        Type: Number

  • If you set Count to 5 and ParallelCount to 2, the system generates the following processed template:

    ROSTemplateFormatVersion: '2015-09-01'
    Resources:
      WaitConditionHandle[0]:
        Type: ALIYUN::ROS::WaitConditionHandle
      WaitConditionHandle[1]:
        Type: ALIYUN::ROS::WaitConditionHandle
      WaitConditionHandle[2]:
        Type: ALIYUN::ROS::WaitConditionHandle
        DependsOn: WaitConditionHandle[0]
      WaitConditionHandle[3]:
        Type: ALIYUN::ROS::WaitConditionHandle
        DependsOn: WaitConditionHandle[1]
      WaitConditionHandle[4]:
        Type: ALIYUN::ROS::WaitConditionHandle
        DependsOn: WaitConditionHandle[2]
    Parameters:
      Count:
        Type: Number
      ParallelCount:
        Type: Number

  • If you set Count to 5 and ParallelCount to 3, the system generates the following processed template:

    ROSTemplateFormatVersion: '2015-09-01'
    Resources:
      WaitConditionHandle[0]:
        Type: ALIYUN::ROS::WaitConditionHandle
      WaitConditionHandle[1]:
        Type: ALIYUN::ROS::WaitConditionHandle
      WaitConditionHandle[2]:
        Type: ALIYUN::ROS::WaitConditionHandle
      WaitConditionHandle[3]:
        Type: ALIYUN::ROS::WaitConditionHandle
        DependsOn: WaitConditionHandle[0]
      WaitConditionHandle[4]:
        Type: ALIYUN::ROS::WaitConditionHandle
        DependsOn: WaitConditionHandle[1]
    Parameters:
      Count:
        Type: Number
      ParallelCount:
        Type: Number