DistributedContext specification is incomplete

[Oberon00]

• The distributed context specification talks about scope (in the conflict resolution section) but does not define it.
• Relatedly, there is no notion of a current context and consequently no way to get it.
• The API, as defined in the spec, provides no way to add values to the distributed context.

In Java, all of this is implemented in the DistributedContextManager (it seems that Tracer : Span ~ DistributedContextManager : DistributedContext).

[Oberon00]

Should this be rectified in a simple PR (that simply follows the Java "reference" implementation) or is an OTEP required?

[songy23]

DistributedContext may be renamed. See open-telemetry/oteps#36.

[Oberon00]

I assume that was just a side note, since renaming would not change anything about the points I raised 😃

[tedsuo]

@Oberon00 in short, the current API is half baked and we hope to finish baking it this week. :)

There's was a lot of discussion last week to hammer out details around DistributedContext. You can find the notes here, under "Context Propagation Discussion": https://docs.google.com/document/d/1rgXZik2_-2fU1KpVi7nze5ygWA8NhaLE8VmD20H4P8M/edit#heading=h.o5slz8bi8org

We hope to get some proposals out this week, based on this discussion, which will hopefully provide a cleaner proposal for context propagation in general.

[tedsuo]

This work has continued as an OTEP: open-telemetry/oteps#66