Referring to blueprint properties, attributes, and parameters

Each blueprint begins with a list of parameters. You can specify these parameters in the blueprint, in a configuration file, or at provisioning time. For example, the following code lists the parameter flavor, which represents the size of a provisioned image, and the parameter key_name, which represents the security key for a provisioned image.

parameters:
  flavor:
    type: string
    description: Flavor to be used for compute instance
    default: "m1.small"
  key_name:
    type: string
    description: Name of key-pair to be used for compute instance
    default: "MyKey"

To refer to these parameters in other places in the blueprint, use the get_param function. For example, the following code shows a server node. The properties for the node refer to the parameters in the previous example.

web-server:
  type: OS::Nova::Server
  properties:
    flavor: { get_param: flavor }
    image: "14243a29-9662-4b9d-b164-67884876fc91"
    key_name: { get_param: key_name }
    name: "web-server"

To refer to an attribute, use the get_attr function. For example, assume that the database node is set up as in the following blueprint code:

db-server:
  type: OS::Nova::Server
  properties:
    networks:
        - port: { get_resource: db-server_external-net_port }
    flavor: { get_param: flavor }
    image: "19033a29-9662-4b9d-b164-67884876fc91"
    key_name: { get_param: key_name }
    name: "db-server"

This node, which is of the resource type OS::Nova::Server, has an attribute that is named networks. This attribute is not shown in the code; it is implied by the resource type. (The code shows a property that is named networks, which is not to be confused with the attribute with the same name.) For information about the properties and attributes on Heat resources, see the reference for the resource type. See Heat resource types.

To view the value of the networks attribute for the database node, specify it in the output section of the blueprint code, as shown in the following code:

outputs:
  networks:
    description: networks
    value: {get_attr: [db-server_external-net, networks]}

The web application can refer to the attribute to retrieve the database IP address. As an example, the web component might have the following blueprint code:

web-component:
  type: IBM::UrbanCode::SoftwareDeploy::UCD
  properties:
    apply_config: { get_resource: web-component_sw_config }
    server: web-server
    version: 5.1
    agent_timeout: "360"
    inputs:
      db-server-ip: { get_attr: [db-server, networks, external-net, 0] }

This code shows a custom property that is named db-server-ip, which represents the IP address of the database node. To get the IP address, the code uses the get_attr function. The arguments of the function refer first to the resource db-server, then to the attribute networks. The attribute networks is a map (a Python dict type) that lists the network resources to which the database node is attached and the IP addresses in those networks. For example, an OpenStack system might have two networks: an internal network with IP addresses for use within the network and an external network with externally accessible floating IP addresses. This map might look like the following example:

{
  "internal-net":[192.168.80.11, 192.168.80.12],
  "external-net":[172.24.50.21, 172.24.50.22]
}

This map lists the IP addresses that are assigned to the resource. The IP addresses are organized according to the network to which the IP address belongs. This example lists two internal network IP addresses and two external network IP addresses. The last two arguments in the get_attr function in the example refer to the name of the network and the index of the IP address, based on this map.

In this way, the following example of the get_attr function refers to the resource db-server, the attribute networks, the network external-net, and the first IP address in the network that is assigned to the resource.

{ get_attr: [db-server, networks, external-net, 0] }