sdk-common: add InstrumentationScope

[iRevive]

Reference	Link
Spec	https://opentelemetry.io/docs/specs/otel/glossary/#instrumentation-scope https://opentelemetry.io/docs/specs/otel/trace/api/#get-a-tracer
Java implementation	InstrumentationScopeInfo.java

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I started decoupling #325 into smaller changes to simplify the review process.

[armanbilge]

I guess the Java SDK calls this InstrumentationScopeInfo, any commentary?

[iRevive]

The specification doesn't require this particular name.
Java SDK uses InstrumentationScopeInfo, Go stands with Scope, Python uses InstrumentationInfo and Rust uses InstrumentationLibrary.

From what I see, InstrumentationScope is sufficient enough and not verbose.

[armanbilge]

Python uses InstrumentationInfo

Wait a minute: Python has both an InstrumentationInfo and an InstrumentationScope. What's the difference? 🤔

[iRevive]

Spec-wise, perhaps they refer to InstrumentationLibrary and InstrumentationScope?

In JavaScript, there are both InstrumentationLibrary and InstrumetnationScope. InstrumentationLibrary is deprecated, though.

[armanbilge]

Actually these can be combined into a single class, then we save an allocation in the build method.

[iRevive]

I don't see reasons why we shouldn't :)

[armanbilge]

I don't want to be bikeshedding too much, it's not a big deal. And I guess otel4s already has some established idioms. But typically I associate set with mutability and e.g. withVersion would be more appropriate for an immutable builder like this one.

[iRevive]

Valid point. We primarily use with* across the otel4s codebase.

[iRevive]

I've updated the code

[NthPortal]

should this be in core-common and used by TracerBuilder? also, to continue what Arman said, should setAttributes be named withAttributes?

bikeshedding that more: currently it only supports replacing the attributes. should we support adding additional attributes as well? instead? we could have withAdditionalAttributes as well. or, we could have withAttributes take a function Attributes => Attributes so that you could either entirely replace the attributes or add additional ones

[iRevive]

should this be in core-common and used by TracerBuilder?

I don't think so. InstrumentationScope is primarily used by the internals: span processors, exporters, etc. End users shouldn't use it directly.

For example, tracer builder public API does not require InstrumentationScope: https://opentelemetry.io/docs/specs/otel/trace/api/#get-a-tracer. But most of the implementation will construct one under the hood.

should setAttributes be named withAttributes?

Definitely. I forgot to rename it.

we could have withAdditionalAttributes as well

I didn't find such a use case (at least yet). Since it is supposed to be used by internals, we can always add it in the future.