Resources API: package, semantic conventions, and test utils

[mwear]

Which problem is this PR solving?

• This is an effort towards completing Add Resource API #789 Resources API.

Short description of the changes

• Extracted the current resource implementation into opentelemetry/resources with a dependency on opentelemetry/api
• Loosened the restriction on label values from string to string, numeric, or boolean
• Added constants for resource semantic conventions from the specification

Next

This PR only provides modeling of Resources, constants for the semantic conventions, and test utilities to validate a resource for conforming to the conventions.

According to the Resource spec spans and metrics should be associated with a resource: https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/sdk-resource.md#resource-sdk

At the Spec SIG call there was confusion over how this should be done and I created this issue for clarification: open-telemetry/opentelemetry-specification#491.

I suspect there will be additional work to associate telemetry with resources, but am proposing that we handle that in a subsequent PR as we get clarification. The approach that Ruby is taking is described in: open-telemetry/opentelemetry-specification#491 and we can go that route if we choose to.

I have also noticed that OpenCensus node has automatic resource detection, these are for system, cloud, container resources: open-telemetry/opentelemetry-specification#491. We should decide what logic we would like to port from Census. Again, I think we can handle these as separate PRs.

[codecov-io]

Codecov Report

Merging #815 into master will decrease coverage by 1.64%.
The diff coverage is 58.82%.

@@            Coverage Diff             @@
##           master     #815      +/-   ##
==========================================
- Coverage   94.55%   92.91%   -1.65%     
==========================================
  Files         249      246       -3     
  Lines       10751    10868     +117     
  Branches     1060     1066       +6     
==========================================
- Hits        10166    10098      -68     
- Misses        585      770     +185

Impacted Files	Coverage Δ
...telemetry-tracing/test/BasicTracerRegistry.test.ts	100% <ø> (ø)	⬆️
packages/opentelemetry-tracing/src/Tracer.ts	96.55% <ø> (-0.17%)	⬇️
packages/opentelemetry-api/src/trace/NoopTracer.ts	100% <ø> (ø)	⬆️
packages/opentelemetry-api/test/api/api.test.ts	96.66% <ø> (ø)	⬆️
packages/opentelemetry-tracing/src/config.ts	100% <ø> (ø)	⬆️
...-api/test/noop-implementations/noop-tracer.test.ts	100% <ø> (ø)	⬆️
...opentelemetry-node/test/NodeTracerProvider.test.ts	100% <ø> (ø)	⬆️
packages/opentelemetry-api/src/api/propagation.ts	58.82% <58.82%> (ø)
...s/opentelemetry-core/test/context/B3Format.test.ts	50% <0%> (-50%)	⬇️
packages/opentelemetry-core/test/utils/url.test.ts	50% <0%> (-50%)	⬇️
... and 50 more

[vmarchaud]

I believe that since it's only interface/enums, we should put that inside @opentelemetry/api

[dyladan]

I believe that since it's only interface/enums, we should put that inside @opentelemetry/api

This is not just interfaces/enums. Also, I don't believe that resource is meant to be exposed by the API, but is a SDK concern.

[mwear]

I've taken this out of draft and into ready for review. I also updated the comment with a description of the current state of resources and the future work that we need to have clarified and make decisions on. I'm happy to take up any of that work in future PRs, or as part of this one if that's what we decide.

[obecny]

lgtm, just minor things

[vmarchaud]

👍

[mayurkale22]

Overall LGTM, added one minor nit.

[dyladan]

Unused dep

[OlivierAlbertini]

LGTM