Cloud Assembly expressions

For increased flexibility, you can add expressions to cloud template code in Cloud Assembly.

How expressions work

Cloud Assembly expressions use the ${expression} construct, as shown in the following examples.

Note: Cloud Assembly expressions aren't the same as regular expressions. See the expression syntax for Cloud Assembly.

The following code samples are pruned to show only the important lines. The entire, unedited cloud template appears at the end.

Examples

At deployment time, allow the user to paste in the encrypted key needed for remote access:

inputs:
  sshKey:
    type: string
    maxLength: 500
resources:
  frontend:
    type: Cloud.Machine
    properties:
      remoteAccess:
        authentication: publicPrivateKey
        sshKey: '${input.sshKey}'

For deploying to VMware Cloud on AWS, set the folder name to the required name of Workload:

inputs:
  environment:
    type: string
    enum:
      - AWS
      - vSphere
      - Azure
      - VMC
      - GCP
    default: vSphere
resources:
  frontend:
    type: Cloud.Machine
    properties:
      folderName: '${input.environment == "VMC" ? "Workload" : ""}'

At deployment time, tag the machine with an all-lowercase env tag that matches the selected environment:

inputs:
  environment:
    type: string
    enum:
      - AWS
      - vSphere
      - Azure
      - VMC
      - GCP
    default: vSphere
resources:
  frontend:
    type: Cloud.Machine
    properties:
      constraints:
        - tag: '${"env:" + to_lower(input.environment)}'

Set the number of machines in the front-end cluster to one (small) or two (large). Note that the large cluster is set by process of elimination:

inputs:
  envsize:
    type: string
    enum:
      - Small
      - Large
resources:
  frontend:
    type: Cloud.Machine
    properties:
      count: '${input.envsize == "Small" ? 1 : 2}'

Attach machines to the same Default network by binding to the property found in the network resource:

resources:
  frontend:
    type: Cloud.Machine
    properties:
      networks:
        - network: '${resource.Cloud_Network_1.name}'
  apitier:
    type: Cloud.Machine
    properties:
      networks:
        - network: '${resource.Cloud_Network_1.name}'
  Cloud_Network_1:
    type: Cloud.Network
    properties:
      name: Default
      networkType: existing

Encrypt access credentials submitted to the API:

resources:
  apitier:
    type: Cloud.Machine
    properties:
      cloudConfig: |
        #cloud-config
        runcmd:
          - export apikey=${base64_encode(input.username:input.password)}
          - curl -i -H 'Accept:application/json' -H 'Authorization:Basic :$apikey' http://example.com

Discover the address of the API machine:

resources:
  frontend:
    type: Cloud.Machine
    properties:
      cloudConfig: |
        runcmd:
          - echo ${resource.apitier.networks[0].address}
  apitier:
    type: Cloud.Machine
    properties:
      networks:
        - network: '${resource.Cloud_Network_1.name}'

Complete cloud template

inputs:
  environment:
    type: string
    enum:
      - AWS
      - vSphere
      - Azure
      - VMC
      - GCP
    default: vSphere
  sshKey:
    type: string
    maxLength: 500
  envsize:
    type: string
    enum:
      - Small
      - Large
resources:
  frontend:
    type: Cloud.Machine
    properties:
      folderName: '${input.environment == "VMC" ? "Workload" : ""}'
      image: ubuntu
      flavor: medium
      count: '${input.envsize == "Small" ? 1 : 2}'
      remoteAccess:
        authentication: publicPrivateKey
        sshKey: '${input.sshKey}'
      cloudConfig: |
        packages:
          - nginx
        runcmd:
          - echo ${resource.apitier.networks[0].address}
      constraints:
        - tag: '${"env:" + to_lower(input.environment)}'
      networks:
        - network: '${resource.Cloud_Network_1.name}'
  apitier:
    type: Cloud.Machine
    properties:
      folderName: '${input.environment == "VMC" ? "Workload" : ""}'
      image: ubuntu
      flavor: small
      cloudConfig: |
        #cloud-config
        runcmd:
          - export apikey=${base64_encode(input.username:input.password)}
          - curl -i -H 'Accept:application/json' -H 'Authorization:Basic :$apikey' http://example.com
      remoteAccess:
        authentication: publicPrivateKey
        sshKey: '${input.sshKey}'
      constraints:
        - tag: '${"env:" + to_lower(input.environment)}'
      networks:
        - network: '${resource.Cloud_Network_1.name}'
  Cloud_Network_1:
    type: Cloud.Network
    properties:
      name: Default
      networkType: existing
      constraints:
        - tag: '${"env:" + to_lower(input.environment)}'