How can I append (resource) attributes of spans in new attributes?

[heiko-holz]

I'd like to append (resource) attributes of spans in a new attribute.
E.g., we have the attributes

service: service-a
namespace: my-namespace

and now I want to append the attributes service and namespace in a new attribute instance, .i.e.,
instance: service-a.my-namespace.

Is there a direct way to append attributes?

I am currently using a workaround with the span and transform processor in the following way:

1. First, I store the span's original name in the attribute span.name.original using a transform processor (alternatively, I use the span processor) :

  transform/1:
    traces:
      queries:
        # store the span's original name as an attribute
        - set(attributes["span.name.original"], name)

2. I then use the span processor to append the attributes in the span's name

  span/name-proxy:
    name:
      from_attributes: [service, namespace] 
      separator: '.'

3. and finally I restore the span's original name and set the instance attribute using the transform processor:

    transform/2:
      traces:
        queries:
          - set(attributes["instance"], name)
          - set(name, attributes["span.name.original"])

How can I achieve the desired behavior more easily?

[t03apt]

  transform/attributes:
    metric_statements:
      - context: datapoint
        statements:
        - set(attributes["k8s_pod_name"], resource.attributes["service.instance.id"])

https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/exporter/prometheusexporter/README.md