[extension/k8sobserver] Discovering "Ports" should populate variable `container_name`

[ChristianCiach]

Component(s)

extension/observer/k8sobserver

Is your feature request related to a problem? Please describe.

When using the k8s_observer to discover container-ports, the container-name of the discovered port is not made available as part of the endpoint details, even though the information is readily available when the results are assembled.

See relevant code:

opentelemetry-collector-contrib/extension/observer/k8sobserver/pod_endpoint.go

Lines 74 to 91 in 77be382

	// Create endpoint for each named container port.
	for _, port := range container.Ports {
	endpointID = observer.EndpointID(
	fmt.Sprintf(
	"%s/%s(%d)", podID, port.Name, port.ContainerPort,
	),
	)
	endpoints = append(endpoints, observer.Endpoint{
	ID: endpointID,
	Target: fmt.Sprintf("%s:%d", podIP, port.ContainerPort),
	Details: &observer.Port{
	Pod: podDetails,
	Name: port.Name,
	Port: uint16(port.ContainerPort),
	Transport: getTransport(port.Protocol),
	},
	})
	}

Why do I need the container name the port belongs to?

I want to configure my receivercreator-receiver like this:

receivers:
  receiver_creator/prometheus:
    watch_observers: [k8s_observer]
    receivers:
      prometheus:
        rule: >-
          type == "port" 
          && pod.annotations["prometheus.io/scrape"] == "true"
          && (pod.annotations["prometheus.io/port"] ?? "9090") == port
        resource_attributes:
          k8s.container.name: "`container_name`"
        config: '...'

Why don't I just use type == "pod"?

When using type == "pod", there is no way to get the k8s.container.name the prometheus.io-annotation targets. I need the k8s.container.name so that the k8sattributes-processor can set service.instance.id, since this relies on the k8s.container.name as described in https://opentelemetry.io/docs/specs/semconv/non-normative/k8s-attributes/#how-serviceinstanceid-should-be-calculated

Why don't I just use type == "pod.container"?

This rule would match multiple containers against the same prometheus-annotations, as there is no way to match the discovered container against the given annotation. The only container-identifying information inside the prometheus-annotations seems to be the port-number, but the discovered ports are not available when using type == "pod.container".

Describe the solution you'd like

Please add the container_name to the discovered ports, just as it's already done when discovering containers.

The container-name is readily available when constructing the endpoint details, so the required changes seem to be minimal.

Describe alternatives you've considered

No response

Additional context

No response

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[github-actions]

Pinging code owners:

• extension/observer/k8sobserver: @dmitryax @ChrsMark

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[ChristianCiach]

I don't currently need it, but maybe we should go all the way and also expose container_id and container_image.

[KyriosGN0]

i will take a look at this 👀