* Update License header for all source files
- Add Apache 2.0 header to source files that did not have one.
- Update all existing headers dated to 2019 to be 2020
- Remove comma from License header to comply with the Apache 2.0
guidelines.
* Update Copyright notice
Use the standard Copyright notices outlined by the
[CNCF](https://github.com/cncf/foundation/blob/master/copyright-notices.md#copyright-notices)
* Remove binary propagators
They are in process of being dropped from the specification and we
haven't be using them anywhere in the project. Can reintroduce them
later.
* Rename Supplier to HTTPSupplier
The supplier is used only in HTTP propagators currently. It's not
clear if it will be useful for binary propagators if they get to be
specified at some point.
* Rework propagation interfaces
The biggest change here is that HTTP extractors return a new context
with whatever information the propagator is able to retrieve from the
supplier. Such interface does not hardcode any extractor's
functionality (like it was before by explicitly returning a span
context and correlation context) and makes it easy to chain multiple
propagators.
Injection part hasn't changed.
* Add Propagators interface
This interface (and its default implementation) is likely going to be
the propagation API used the most. Single injectors, extractors or
propagators are likely going to be used just as parameters to the
Option functions that configure the Propagators implementation.
* Drop noop propagator
It's rather pointless - just create an empty Propagators instance.
* Fix wrong name in docs
Co-authored-by: Joshua MacDonald <jmacd@users.noreply.github.com>
This PR removes the non-compliant ChildOf and FollowsFrom interfaces
and the Relation type, which were inherited from OpenTracing via the
initial prototype. Instead allow adding a span context to the go
context as a remote span context and use a simple algorithm for
figuring out an actual parent of the new span, which was proposed for
the OpenTelemetry specification.
Also add a way to ignore current span and remote span context in go
context, so we can force the tracer to create a new root span - a span
with a new trace ID.
That required some moderate changes in the opentracing bridge - first
reference with ChildOfRef reference type becomes a local parent, the
rest become links. This also fixes links handling in the meantime. The
downside of the approach proposed here is that we can only set the
remote parent when creating a span through the opentracing API.
Co-authored-by: Joshua MacDonald <jmacd@users.noreply.github.com>
* Rename distributedcontext package to correlation
Correlation is the name we agreed upon.
* Move trace propagators to api/trace
The trace propagators tests had to be moved to a testtrace subpackage
to avoid import cycles between api/trace and internal/trace.
Needed to shut up golint about stutter in trace.TraceContext -
TraceContext is a name of a W3C spec, so this stutter is
expected. It's certainly still better than golint's suggestion of
having trace.Context.
* Rename api/propagators to api/propagation
This package will not contain any propagators in the long run, just
the interface definitions.
Co-authored-by: Joshua MacDonald <jmacd@users.noreply.github.com>
