Fill service.instance.id with UUID by default

[anuraaga]

A user, or other resource provider, may specify a better service.instance.id, but by default we should add a UUID as recommended by the spec.

https://github.com/open-telemetry/opentelemetry-specification/tree/master/specification/resource/semantic_conventions#service

[jkwatson]

If the spec were updated to make this field mandatory (which I know has been discussed), then this seems like it would be an important fallback to add to Resource.getDefault(). For the nonce, I don't think we should do this without the spec making it required.

Do you think this is something that one of the resource auto-detectors should provide?

[jkwatson]

Do you think this is something that one of the resource auto-detectors should provide?

ping @anuraaga

[anuraaga]

It's been a while since I filed open-telemetry/opentelemetry-specification#1034 (comment) about not understanding this attribute. I think it's still not a good attribute, for the reason @Oberon00 mentions too :) So will just close this issue