Example / proof of concept to achieve a combination of head-based sampling + a basic form of tail-based sampling at a span level.

[kalyanaj]

This is an example / proof of concept to achieve a combination of head-based sampling + a basic form of tail-based sampling at a span level.
Fixes #4205 .

Changes

This is an exploration/proof of concept of Tail-based sampling at a span level by using the extensibility mechanisms in the SDK. This is a way to achieve a combination of head-based sampling (based on probabilistic sampling) and a way to get all failure spans (non-probabilistic sampling: e.g., based on failure spans).

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

• Appropriate CHANGELOG.md updated for non-trivial changes
• Design discussion issue #
• Changes in public API reviewed

[codecov]

Codecov Report

Merging #4206 (4ed2c69) into main (a1ea6d6) will increase coverage by 0.00%.
The diff coverage is n/a.

❗ Current head 4ed2c69 differs from pull request most recent head 20bbdcf. Consider uploading reports for the commit 20bbdcf to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4206   +/-   ##
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  Coverage   84.42%   84.43%           
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  Files         298      298           
  Lines       11851    11851           
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+ Hits        10005    10006    +1     
+ Misses       1846     1845    -1     

see 3 files with indirect coverage changes

[cijothomas]

LGTM. Left few small comments. Please address them before merging. Thank you!