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Resource Orchestration Service:Resources

Last Updated:Dec 26, 2023

In the Resources section, you can define the properties of each resource that is contained in a stack and the dependencies between resources. A resource can be referenced by other resources and output items. This topic describes the information about the Resources section.

Resource types

Resource types are classified into regular resources and data source resources. Regular resources can be further classified into Alibaba Cloud resources and custom resources. The following table describes the resource types.

Resource type

Description

Regular resource (Resource)

  • You can create Alibaba Cloud resources, and update and delete the resources. Alibaba Cloud resources must start with ALIYUN::.

  • You can create custom resources based on the logic that you define, and define how the resources are updated and deleted. Custom resources must start with Custom:: or ALIYUN::ROS::CustomResource.

    For more information, see Overview.

Data source resource (DataSource)

You can use data source resources to query the resource data of Alibaba Cloud services.

For more information, see Data source resources.

Syntax

A resource consists of an ID and a description. All resource descriptions must be enclosed in braces ({ }). If you declare multiple resources, you must separate the resources by commas (,). The following sample code provides an example on the syntax of the Resources section:

Resources:
  ID of Resource 1:
    Type: the resource type.
    Condition: the condition based on which the resource is created.
    Properties: the descriptions of resource properties.
  ID of Resource 2:
    Type: the resource type.
    Condition: the condition based on which the resource is created.
    Properties: the descriptions of resource properties.

Fields in the Resources section:

  • A resource ID must be unique in a template. You can use the resource ID to reference the resource in other sections of a template.

  • Type: the type of the resource that you declare. For example, if you set Type to ALIYUN::ECS::Instance, the resource that you declare is an Elastic Compute Service (ECS) instance. For more information about resource types that are supported by Resource Orchestration Service (ROS), see List of resource types by service.

  • Properties: the additional options that you specify for the resource. For example, you must specify an image ID for each ECS instance. In this case, the image ID is a resource property.

Example:

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

If you do not need to declare properties for a resource, leave Properties empty.

Property values can be text strings, string lists, booleans, referenced parameters, or return values of functions. The following information describes the 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

DeletionPolicy

You can specify the DeletionPolicy property in a template to retain a specified resource when a stack is deleted. 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

In the preceding example, the system retains the resource ECSInstance when the stack that is created based on the template is deleted.

DependsOn

You can specify the DependsOn property in a template to create a specific resource only after its dependent resource is created. If you specify the DependsOn property for a resource, the system creates the resource only after its dependent resources specified in the DependsOn property are created.

Important

You can set the Condition property of a dependent resource that is specified in the DependsOn property to False. A value of False specifies that the resource is created even if the dependent resource fails to be created.

The following sample code provides examples on how to configure dependent resources:

  • Configure a single dependent resource.

    DependsOn: ResourceName
  • Configure multiple dependent resources.

    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

Condition

You can specify the Condition property in a template to determine whether to create a resource. The system can create the resource only when the condition that you specify for the Condition property is met.

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

Count

You can specify the Count property for a resource in a template to preprocess the template and replace the resource with multiplied resources. When you use a template for which the Count property is specified to perform operations on a stack, the system uses the processed template.

  • For example, you set the Count property of Resource A to 3 in the original template. After ROS preprocesses 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 on the original template:

    Resources:
      A:
        Count: 3
        ...: Null
      ...: Null

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

    Resources:
      A[0]:
        ...: Null
      A[1]:
        ...: Null
      A[2]:
        ...: Null
      ...: Null
    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 preprocessed and validated.

    If you specify Count for a resource, the resource name is changed. We recommend that you do not add the Count property to existing resources to prevent deletion of the resources.

  • The value of the Count property must be a natural number. The property value supports only the following functions. You can invoke only the Ref function in Count to reference parameters.

  • The maximum number of resources in a processed template cannot exceed 300.

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

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

    DependsOn: A

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

    DependsOn:
      - A[0]
      - A[1]
      - A[2]
  • If you specify Count for a resource and specify the resource in Ref and Fn::GetAtt, the resource is replaced with multiplied resources. The following sample code provides an example on the original template:

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

    The following sample code provides an example on 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 Count together with Fn::Select and ALIYUN::Index.

    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 also 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

The following sample code provides an example on how to specify the Count property in the original template. In this template, a group of Elastic IP addresses (EIPs) and ECS instances are created, and each EIP is bound to an ECS instance. The same number of EIPs and ECS instances are created.

ROSTemplateFormatVersion: '2015-09-01'
Parameters:
  Count:
    Type: Number
Resources:
  Eip:
    Type: ALIYUN::VPC::EIP
    Count:
      Ref: Count
    Properties:
      Bandwidth: 5
  Servers:
    Type: ALIYUN::ECS::InstanceGroup
    Properties:
      MinAmount:
        Ref: Count
      MaxAmount:
        Ref: Count
      AllocatePublicIP: false
      ...: Null
  EipBind:
    Type: ALIYUN::VPC::EIPAssociation
    Count:
      Ref: Count
    Properties:
      InstanceId:
        Fn::Select:
          - Ref: ALIYUN::Index
          - Fn::GetAtt:
              - Servers
              - InstanceIds
      AllocationId:
        Fn::Select:
          - Ref: ALIYUN::Index
          - Ref: Eip
Outputs:
  InstanceIds:
    Value:
      Fn::GetAtt:
        - Servers
        - InstanceIds
  AllocationIds:
    Value:
      Ref: Eip
  EipAddresses:
    Value:
      Fn::GetAtt:
        - Eip
        - EipAddress

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

ROSTemplateFormatVersion: '2015-09-01'
Parameters:
  Count:
    Type: Number
Resources:
  Eip[0]:
    Type: ALIYUN::VPC::EIP
    Properties:
      Bandwidth: 5
  Eip[1]:
    Type: ALIYUN::VPC::EIP
    Properties:
      Bandwidth: 5
  Servers:
    Type: ALIYUN::ECS::InstanceGroup
    Properties:
      MinAmount:
        Ref: Count
      MaxAmount:
        Ref: Count
      AllocatePublicIP: false
      ...: Null
  EipBind[0]:
    Type: ALIYUN::VPC::EIPAssociation
    Properties:
      InstanceId:
        Fn::Select:
          - 0
          - Fn::GetAtt:
              - Servers
              - InstanceIds
      AllocationId:
        Ref: Eip[0]
  EipBind[1]:
    Type: ALIYUN::VPC::EIPAssociation
    Properties:
      InstanceId:
        Fn::Select:
          - 1
          - Fn::GetAtt:
              - Servers
              - InstanceIds
      AllocationId:
        Ref: Eip[1]
Outputs:
  InstanceIds:
    Value:
      Fn::GetAtt:
        - Servers
        - InstanceIds
  AllocationIds:
    Value:
      - Ref: Eip[0]
      - Ref: Eip[1]
  EipAddresses:
    Value:
      - Fn::GetAtt:
          - Eip[0]
          - EipAddress
      - Fn::GetAtt:
          - Eip[1]
          - EipAddress

Resource declaration example

The following example shows how to declare resources:

Resources:
  WebServer:
    Type: ALIYUN::ECS::Instance
    Properties:
      ImageId: m-25l0r****
      InstanceType: ecs.t1.small
      SecurityGroupId: sg-25zwc****
      ZoneId: cn-beijing-b
      Tags:
        - Key: Department1
          Value: HumanResource
        - Key: Department2
          Value: Finance
  ScalingConfiguration:
    Type: ALIYUN::ESS::ScalingConfiguration
    Properties:
      ImageId: ubuntu_14_04_64_20G_aliaegis_2015****.vhd
      InstanceType: ecs.t1.small
      InstanceId: i-25xhh****
      InternetChargeType: PayByTraffic
      InternetMaxBandwidthIn: 1
      InternetMaxBandwidthOut: 20
      SystemDisk_Category: cloud
      ScalingGroupId: bwhtvpcBcKYac9fe3vd0****
      SecurityGroupId: sg-25zwc****
      DiskMappings:
        - Size: 10
        - Category: cloud
          Size: 10