processor/resourcedetectionprocessor: add fall back method for GKE host name detection

[gbbr]

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

When using Workload Identity in GKE, the host name resolution will fail, resulting in an empty host name attribute.

Describe the solution you'd like

Under normal circumstances, this call returns the instance name. When not available, one could fall back to obtaining the Kubernetes node name from the Kubernetes API (with k8s.io/client-go). The Kubernetes node name is also equal to the instance name.

[github-actions]

Pinging code owners: @jrcamp @Aneurysm9 @dashpole. See Adding Labels via Comments if you do not have permissions to add labels yourself.

[mx-psi]

@dashpole We want your feedback on this. On GKE, instance/name seems to always return the Kubernetes node name. It would be useful to us (Datadog) if this also worked when running under Workload identity, in which case one would have to get it from either the downward API or querying the Kubernetes API server. Is this something the gcp detector should do? If so, how should it do it?

[dashpole]

Generally, I'd like the gcp detector to only retrieve information from gcp-specific metadata sources.

It should not query the Kubernetes API Server. It is already possible to use the downward API today with the env detector to add host.name if you want.

[mx-psi]

That's fair, I understand. Even if we don't do it automatically, I think it would still be helpful to at least document the limitation on Workload identity and suggest using the env detector on the processor's README. Does that make sense?

[dashpole]

I fully support improving documentation :)

[github-actions]

This issue has been inactive for 60 days. It will be closed in 60 days if there is no activity. To ping code owners by adding a component label, see Adding Labels via Comments, or if you are unsure of which component this issue relates to, please ping @open-telemetry/collector-contrib-triagers. If this issue is still relevant, please ping the code owners or leave a comment explaining why it is still relevant. Otherwise, please close it.

Pinging code owners:

• processor/resourcedetection: @jrcamp @Aneurysm9 @dashpole

See Adding Labels via Comments if you do not have permissions to add labels yourself.

[github-actions]

This issue has been inactive for 60 days. It will be closed in 60 days if there is no activity. To ping code owners by adding a component label, see Adding Labels via Comments, or if you are unsure of which component this issue relates to, please ping @open-telemetry/collector-contrib-triagers. If this issue is still relevant, please ping the code owners or leave a comment explaining why it is still relevant. Otherwise, please close it.

Pinging code owners:

• processor/resourcedetection: @Aneurysm9 @dashpole

See Adding Labels via Comments if you do not have permissions to add labels yourself.