feat: AWS X-Ray Remote Sampler Part 2 - Add Rules Caching and Rules Matching Logic

[jj22ee]

Description

• Followup PR of feat: AWS X-Ray Remote Sampler Part 1 - Initial Classes and Rules Poller Implementation #1453

This is the 2nd PR to address #1434 in order for OTel Ruby to support X-Ray Remote Sampling. One more PR to fully implement this feature will follow this one.

Changes:

• Add Sampling RuleCache
  • Caches a list of SamplingRuleAppliers, ordered by rule priority then rule name. Each Rule Applier corresponds to the Sampling Rule from GetSamplingRules. Each call to GetSamplingRules will only update the Rules that have changed properties, to preserve the state of unchanged rules. This means when Reservoir and Statistics are implemented (later) in the Rules, they will persist for unchanged rules.
  • The RuleCache will determine which Rule a set of {ResourceAttributes,SpanAttributes} matches with that has highest priority.
• Update SamplingRuleApplier to perform Fixed Rate Sampling, and to include a method to apply matching logic against a set of {ResourceAttributes,SpanAttributes} by using the wild card and attribute matching from Utils
• Initial class for FallbackSampler
• Update X-Ray Remote Sampler to depend on the SamplingRuleApplier from RuleCache and the FallBack Sampler to perform should_sample?

Testing

• Unit Tests
• The current implementation was tested against X-Ray's Centralized Sampling Integration tests. The tests for applying Fixed Rate sampling from X-Ray Sampling Rules worked, while the Reservoir sampling from X-Ray Sampling Rules failed (expected since the implementation is incomplete)

[jj22ee]

@lukeina2z Need your help reviewing. Currently everything is implemented except for Updating Sampling Targets and the Rate Limiting (Reservoir) Sampler.

[jj22ee]

PR is ready for merge from our end.

[kaylareopelle]

Overall, this looks great! I have a few small questions/comments.

Thanks for your patience!

[kaylareopelle]

Thanks for the updates and for your patience @jj22ee. Looking forward to the next PR!