Prototype for W3C Trace Context Level 2 support in TraceIDRatioBased sampler

[jmacd]

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This is a prototype implementation for changes to the TraceIDRatioBased sampler based on W3C Trace Context Level 2 which includes support for trace randomness.

This is a combined prototype for the SDK-relevant portions of https://github.com/open-telemetry/opentelemetry-specification/pull/4162 and https://github.com/open-telemetry/opentelemetry-specification/pull/4166.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 84.5%. Comparing base (2a454a7) to head (36a41d9). Report is 192 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff           @@
##            main   #5645    +/-   ##
======================================
  Coverage   84.4%   84.5%            
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  Files        272     272            
  Lines      22506   22679   +173     
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+ Hits       19017   19166   +149     
- Misses      3153    3172    +19     
- Partials     336     341     +5     

see 8 files with indirect coverage changes

[pellared]

Do we have some benchmarks that would demonstrate the overhead of the added randomness support? Can we add benchstat results?

[jmacd]

The sampling SIG is pursuing a new "optional" sampler API that will improve the performance of this feature. https://github.com/open-telemetry/opentelemetry-specification/pull/4294