Opentracing shim

[chusitoo]

Fixes #78, answers to #1180

Changes

• Implement Opentracing shim as described in https://opentelemetry.io/docs/reference/specification/compatibility/opentracing/
• Unit tests are a combination of legacy Opentracing tests as well as new tests mimicking the Java and JS counterparts
• Add CMake support (turned off by default) for externally linked Opentracing library or use local submodule
• Add basic build support with Bazel. Windows is unsupported due to Opentracing lacking build support for the platform.

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: chusitoo / name: Alex E. (45e0c4b, 321a801, 36cca42, 81b8557, 1fc7f33, 4d99b85, 22949e2, f62eb78, 25aeac8, 8f10779, 697c402, 2d2adf3, 5d15422, 32ba915, ddd71ab, 4d91681)

[codecov]

Codecov Report

Merging #1909 (ac8dc8f) into main (9a5bb8d) will decrease coverage by 0.02%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1909      +/-   ##
==========================================
- Coverage   87.32%   87.29%   -0.02%     
==========================================
  Files         166      166              
  Lines        4673     4673              
==========================================
- Hits         4080     4079       -1     
- Misses        593      594       +1     

Impacted Files	Coverage Δ
sdk/src/trace/batch_span_processor.cc	90.70% <0.00%> (-0.77%)	⬇️

[owent]

Is it better to move this into a standalone directory?

[lalitb]

Thanks for the PR. Tagging @rnburn as someone contributed to both otel-cpp and opentracing-cpp if he would like to review this. though I don't see him active on Github for long now, just trying the luck :)

[marcalff]

The copyright check in CI is new, please fix:

Missing copyright in ./opentracing-shim/BUILD
Missing license in ./opentracing-shim/BUILD
Missing copyright in ./opentracing-shim/CMakeLists.txt
Missing license in ./opentracing-shim/CMakeLists.txt

[marcalff]

In third_party/prometheus-cpp, the git submodule for prometheus changed.

It looks like a merge issue with:

commit 9200d0c8fb4684e5fffd2c6915c8117a747c8e2b
Author: Lalit Kumar Bhasin <lalit_fin@yahoo.com>
Date:   Sat Feb 4 20:32:33 2023 -0800

    upgrade prometheus-cpp to v1.1.0 (#1954)

Please fix.

[marcalff]

@chusitoo

If I understand correctly, the Opentracing shim introduces a dependency on the opentracing-cpp repository, which is a deprecated library, per:

opentracing/specification#163

It is a bit unusual to add dependencies like that, but it makes sense in this case, so ok.

Not knowing enough of Opentracing, it is a bit hard to review the code for correctness for every details.

That said, the overall code looks ok.

The contributed code is protected by a WITH_OPENTRACING option, and is separate from the opentelemetry-cpp code which is otherwise unchanged, so there is very little technical risks with this PR, in my opinion.

SpanContextShim::extractFrom() has a hack with kUniqueTag, but after looking at it I don't have a better proposal to offer, so ok with it.

Please fix the prometheus-cpp spurious change, and I will approve this PR.

Great work.

[marcalff]

LGTM, thanks for the contribution.

[lalitb]

Sorry for responding late on it. Changes in general look good, and clean approach - the shim confined to separate directory, and behind feature flag.
Most of the existing contributors doesn't have expertise on Opentracing, and bandwidth to manage this component, so @chusitoo it would be appreciated if you can own any related issues/changes going ahead :)

[chusitoo]

Sorry for responding late on it. Changes in general look good, and clean approach - the shim confined to separate directory, and behind feature flag. Most of the existing contributors doesn't have expertise on Opentracing, and bandwidth to manage this component, so @chusitoo it would be appreciated if you can own any related issues/changes going ahead :)

@lalitb Thanks for the review. Not a problem, I am not an expert in OpenTracing myself but I can support any related issues or requests related to the shim.