Introduce Entities Data Model, Part 1

[tigrannajaryan]

This is a proposal of a data model to represent entities. The purpose of the data model is to have a common understanding of what an entity is, what data needs to be recorded, transferred, stored and interpreted by an entity observability system.

This data model sets the foundation for adding entities to OpenTelemetry. The data model is largely borrowed from
the initial proposal that was accepted for entities SIG formation.

This OTEP is step 1 in introducing the entities data model. Follow up OTEPs will add further data model definitions, including the linking of Resource information to entities.

[jack-berg]

Couple of comments that can be worked out in future work but this looks great to me. Thanks for putting this together!

[mx-psi]

LGTM. I haven't been able to join the Entities meeting but this looks like a good start to me and it seems like this way of approaching identity is better than the alternatives

[tigrannajaryan]

@open-telemetry/specs-approvers please review.

[pellared]

I reviewed only ~100 lines so far

[bidetofevil]

This new concept is great, and (I think) it provides a much more elegant solution to how we can model frequently-changing, mutable state(s) that have an outsized impact of how mobile applications run in production. The ability to model network connections, OS resource provisioning (e.g. CPU throttling, process priority, etc.), concurrent app execution, OS services and state, etc. as one or more entities in a consistent, semantic convention'd manner will go a long way into standardizing the execution context of mobile apps, something we sorely need.

[tigrannajaryan]

All reviewers, thank you for your comments and improvement suggestions. I think I addressed all questions.

I will keep the PR open for 2 more business days and will merge after that if I see no objections.

[tigrannajaryan]

2 business days since last change. All comments addressed and resolved. We have enough approvals. Merging.

[mjwolf]

Hi @tigrannajaryan, I know this is only an example, but I'd like to point out this won't be sufficient for a unique process entity ID on Windows.

On Windows, PIDS can be re-used in less than 1s, so to be unique, the start time could be more precise (nanoseconds), or more attributes are needed

[tigrannajaryan]

Yes, just an example and thanks for pointing out. We will work on this most likely within the semconv group when the Entities SIG makes a bit more progress on the basics.