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    Resource Orchestration Service:Use Count to create multiple resources

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    Resource Orchestration Service:Use Count to create multiple resources

    Last Updated:Jun 16, 2026

    Resource Orchestration Service (ROS) provides the Count feature to create multiple resources in batches. This example uses Count to create multiple ECS instances and elastic IP addresses (EIPs) and bind them to their corresponding ECS instances.

    Background

    Provisioning an elastic IP address (EIP) requires the ALIYUN::VPC::EIP resource type. Declaring multiple ALIYUN::VPC::EIP resources makes the template verbose. The Count feature lets you create multiple resources efficiently. For more information, see Count. You can also specify the DependsOn attribute and set the ParallelCount parameter to control resource creation concurrency.

    Step 1: Write the template

    This template uses the Count feature to create the following resources:

    • One Virtual Private Cloud (VPC)

    • One vSwitch

    • One security group

    • Four pay-as-you-go ECS instances

    • Four elastic IP addresses (EIPs)

    The following sections provide the sample template and explain its components.

    • Sample template

      ROSTemplateFormatVersion: '2015-09-01'
Parameters:
  Count:
    Type: Number
    Default: 4
  ZoneId:
    Type: String
  InstanceType:
    Type: String
    Default: ecs.c6.large
  Password:
    Type: String
    Default: Abc1****
    NoEcho: true
  ParallelCount:
    Type: Number
    Default: 2
  SystemDiskCategory:
    Type: String
Resources:
  Vpc:
    Type: ALIYUN::ECS::VPC
    Properties:
      CidrBlock: 10.0.0.0/8
      VpcName: test-resource-count
  VSwitch:
    Type: ALIYUN::ECS::VSwitch
    Properties:
      CidrBlock: 10.0.10.0/24
      ZoneId:
        Ref: ZoneId
      VpcId:
        Ref: Vpc
  SecurityGroup:
    Type: ALIYUN::ECS::SecurityGroup
    Properties:
      SecurityGroupName: test-resource-count
      VpcId:
        Ref: Vpc
  Eip:
    Type: ALIYUN::VPC::EIP
    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
              - Eip[index]
    Properties:
      Bandwidth: 5
  Servers:
    Type: ALIYUN::ECS::InstanceGroup
    Properties:
      ImageId: centos_7
      InstanceType:
        Ref: InstanceType
      VpcId:
        Ref: Vpc
      VSwitchId:
        Ref: VSwitch
      SecurityGroupId:
        Ref: SecurityGroup
      Password:
        Ref: Password
      AllocatePublicIP: false
      MaxAmount:
        Ref: Count
      SystemDiskCategory:
        Ref: SystemDiskCategory
  EipBind:
    Type: ALIYUN::VPC::EIPAssociation
    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
              - EipBind[index]
    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

    • Template explanation

      • Create four EIPs.

        The Count parameter is set to 4. Because ParallelCount is set to 2, ROS creates the four EIPs in two batches. After preprocessing, ROS generates four resources: Eip[0] and Eip[1] (Batch 1), then Eip[2] and Eip[3] (Batch 2).

        Eip:
  Type: ALIYUN::VPC::EIP
  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
            - Eip[index]
  Properties:
    Bandwidth: 5

      • Create four ECS instances.

        The Count parameter is set to 4. The MaxAmount property of the ALIYUN::ECS::InstanceGroup resource references the Count parameter to create four ECS instances.

        Servers:
  Type: ALIYUN::ECS::InstanceGroup
  Properties:
    ImageId: centos_7
    InstanceType:
      Ref: InstanceType
    VpcId:
      Ref: Vpc
    VSwitchId:
      Ref: VSwitch
    SecurityGroupId:
      Ref: SecurityGroup
    Password:
      Ref: Password
    AllocatePublicIP: false
    MaxAmount:
      Ref: Count
    SystemDiskCategory:
      Ref: SystemDiskCategory

      • Create four EipBind resources to sequentially bind the ECS instances to the EIPs using the ALIYUN::Index pseudo parameter.

        The Count parameter is set to 4, and ParallelCount is set to 2, so ROS creates the four EipBind resources in two batches. After preprocessing, ROS generates four resources: EipBind[0] and EipBind[1] (Batch 1), then EipBind[2] and EipBind[3] (Batch 2). During preprocessing, ROS replaces ALIYUN::Index with the current iteration number, binding each instance to its corresponding EIP: the first instance to Eip[0], the second to Eip[1], and so on.

        EipBind:
  Type: ALIYUN::VPC::EIPAssociation
  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
            - EipBind[index]
  Properties:
    InstanceId:
      Fn::Select:
        - Ref: ALIYUN::Index
        - Fn::GetAtt:
            - Servers
            - InstanceIds
    AllocationId:
      Fn::Select:
        - Ref: ALIYUN::Index
        - Ref: Eip

    Step 2: Create a stack

    1. Log on to the ROS console.

    2. In the navigation pane on the left, click Stacks.

    3. In the top navigation bar, select the region where you want to create the stack, such as China (Hangzhou).

    4. On the Stacks page, click Create Stack and select Use ROS from the drop-down list.

    5. On the Select Template page, in the Specify Template section, click Select an Existing Template.

    6. In the Template Import Method section, click Enter Template Content, paste the template content from Step 1: Write the template, and then click Next.

    7. On the Configure Parameters page, set the Stack Name and configure the parameters in the Template Parameters section.

    8. In the Configure Stack Settings section, configure Stack Policy, Rollback on Failure, Timeout Period, Deletion Protection, RAM Role, Tags, and Resource Group. Then, click Next.

      If a resource is not created or updated within the specified Timeout Period, the operation fails. The system then uses the Rollback on Failure setting to determine whether to roll back the resources.

    9. On the Compliance Precheck page, complete the compliance check, and then click Next.

      Note

      The compliance precheck feature is available only for specific resources. For more information, see Compliance precheck.

      1. In the Detection Rules section, add detection rules.

        Select detection rules based on the cloud resources defined in the ROS template.

      2. Click Start Check.

        If a resource is found to be Non-compliant, you can click Remediation Plan and modify the cloud resource configuration or ROS template content based on the Remediation Plan to ensure resource compliance.

    10. On the Check and Confirm page, click Create.

    Step 3 (Optional): View resources and template

    After the stack is created, you can view the resources and preprocessed template on the stack details page.

    1. On the stack details page, click the Resources tab to view resource information.

    2. On the stack details page, click the Templates tab to view template information.

      The following code provides an example of the preprocessed template:

      ROSTemplateFormatVersion: '2015-09-01'
Resources:
  EipBind[1]:
    Type: ALIYUN::VPC::EIPAssociation
    Properties:
      InstanceId:
        Fn::Select:
          - 1
          - Fn::GetAtt:
              - Servers
              - InstanceIds
      AllocationId:
        Ref: Eip[1]
  Eip[1]:
    Type: ALIYUN::VPC::EIP
    Properties:
      Bandwidth: 5
  SecurityGroup:
    Type: ALIYUN::ECS::SecurityGroup
    Properties:
      VpcId:
        Ref: Vpc
      SecurityGroupName: test-resource-count
  Servers:
    Type: ALIYUN::ECS::InstanceGroup
    Properties:
      SystemDiskCategory:
        Ref: SystemDiskCategory
      VpcId:
        Ref: Vpc
      SecurityGroupId:
        Ref: SecurityGroup
      ImageId: centos_7
      AllocatePublicIP: false
      VSwitchId:
        Ref: VSwitch
      Password:
        Ref: Password
      InstanceType:
        Ref: InstanceType
      MaxAmount:
        Ref: Count
  Eip[2]:
    Type: ALIYUN::VPC::EIP
    Properties:
      Bandwidth: 5
    DependsOn: Eip[0]
  Eip[0]:
    Type: ALIYUN::VPC::EIP
    Properties:
      Bandwidth: 5
  Vpc:
    Type: ALIYUN::ECS::VPC
    Properties:
      VpcName: test-resource-count
      CidrBlock: 10.0.0.0/8
  Eip[3]:
    Type: ALIYUN::VPC::EIP
    Properties:
      Bandwidth: 5
    DependsOn: Eip[1]
  VSwitch:
    Type: ALIYUN::ECS::VSwitch
    Properties:
      VpcId:
        Ref: Vpc
      CidrBlock: 10.0.10.0/24
      ZoneId:
        Ref: ZoneId
  EipBind[3]:
    Type: ALIYUN::VPC::EIPAssociation
    Properties:
      InstanceId:
        Fn::Select:
          - 3
          - Fn::GetAtt:
              - Servers
              - InstanceIds
      AllocationId:
        Ref: Eip[3]
    DependsOn: EipBind[1]
  EipBind[0]:
    Type: ALIYUN::VPC::EIPAssociation
    Properties:
      InstanceId:
        Fn::Select:
          - 0
          - Fn::GetAtt:
              - Servers
              - InstanceIds
      AllocationId:
        Ref: Eip[0]
  EipBind[2]:
    Type: ALIYUN::VPC::EIPAssociation
    Properties:
      InstanceId:
        Fn::Select:
          - 2
          - Fn::GetAtt:
              - Servers
              - InstanceIds
      AllocationId:
        Ref: Eip[2]
    DependsOn: EipBind[0]
Parameters:
  Count:
    Default: 4
    Type: Number
  SystemDiskCategory:
    Type: String
  ZoneId:
    Type: String
  Password:
    Default: Abc1****
    NoEcho: true
    Type: String
  InstanceType:
    Default: ecs.c6.large
    Type: String
  ParallelCount:
    Default: 2
    Type: Number
Outputs:
  AllocationIds:
    Value:
      - Ref: Eip[0]
      - Ref: Eip[1]
      - Ref: Eip[2]
      - Ref: Eip[3]
  InstanceIds:
    Value:
      Fn::GetAtt:
        - Servers
        - InstanceIds
  EipAddresses:
    Value:
      - Fn::GetAtt:
          - Eip[0]
          - EipAddress
      - Fn::GetAtt:
          - Eip[1]
          - EipAddress
      - Fn::GetAtt:
          - Eip[2]
          - EipAddress
      - Fn::GetAtt:
          - Eip[3]
          - EipAddress