Retrieving attributes from a resource group with a tempate composition - openstack

Question

I want to create multiple copies of some resources defined in a template. How do I retrieve the attributes of the resources created in this fashion.
To illustrate, here is a template to create a random string (I call word.yaml):
heat_template_version: rocky
resources:
word:
type: OS::Heat::RandomString
Because I want a list of such random strings, I use an OS::Heat::ResourceGroup calling the template from word.yaml:
heat_template_version: rocky
resources:
composition:
type: OS::Heat::ResourceGroup
properties:
count: 2
resource_def:
type: word.yaml
outputs:
composition:
value: {get_attr: [composition, resource.word]}
Rubbing together the explanation of OS::Heat::ResourceGroup (ResourceGroup) and the template composition documentation (nested attributes), I expected a list of strings in my output, yet I get:
{
"outputs": [
{
"output_key": "composition",
"description": "No description given",
"output_error": "Member 'word' not found in group resource 'composition'.",
"output_value": null
}
]
}
What am I missing about the interaction of the resource group and the template composition?

Answer 1

Found the answer: I need to specify the attribute to retrieve as outpus of the composition. So the word.yaml would look like this:
heat_template_version: rocky
resources:
word:
type: OS::Heat::RandomString
outputs:
word:
description: the word
value: {get_attr: [word]}
And the composition, like so:
heat_template_version: rocky
resources:
composition:
type: OS::Heat::ResourceGroup
properties:
count: 2
resource_def:
type: word.yaml
outputs:
composition:
value: {get_attr: [composition, word]}
Yielding the expected output:
{
"output_key": "composition",
"description": "No description given",
"output_value": [
{
"value": "gB7ZcXgNjJlEtf8N47yFCOQyH0a1bb9c"
},
{
"value": "wXN4jAKgPqbf5i3GDR6qMkzfC7jF0xdC"
}
]
}