feat: AWS X-Ray Remote Sampler Part 3 - Add Rate Limiter and Sampling Targets Poller Logic

[jj22ee]

Description

• Followup PR of feat: AWS X-Ray Remote Sampler Part 2 - Add Rules Caching and Rules Matching Logic #1498

This is the 3rd and final PR to address #1434 in order for OTel Ruby to support X-Ray Remote Sampling.

Changes:

• Added logic to fetch sampling targets for each sampling_rule_applier.
  • The sampling targets are periodically fetched every 10 seconds by making the GetSamplingTargets API call to X-Ray.
  • The targets determine the reservoir quota and the rate at which a sampling_rule_applier will sample the requests.
  • Each rule applier keeps and updates a sampling statistics document which is required in GetSamplingTargets call to determine the next target
• Added a rate_limiting_sampler (applied before the fixed rate sampler) to be used in each rule applier.
  • Together these samplers determine how many requests to sample every second and what percentage of additional requests to sample in that second.
  • The fallback_sampler is updated to be a combination of above samplers to sample 1 req/sec and 5% of additional requests in that second.
• Added example/xray_sampling_on_rails_demonstration.ru that runs an example rails application that uses the OpenTelemetry X-Ray Sampler, with example instructions in the comments at the bottom of the file.

Testing

• Unit Tests
• The current implementation was tested against X-Ray's Centralized Sampling Integration tests.

[kaylareopelle]

Hi @jj22ee, thanks for your patience. I'll take a look at this PR later today. Will the new gem be ready for release after this PR?

[jj22ee]

Thanks @kaylareopelle! This new gem will be ready for releasing after this PR.

[github-actions]

👋 This pull request has been marked as stale because it has been open with no activity. You can: comment on the issue or remove the stale label to hold stale off for a while, add the keep label to hold stale off permanently, or do nothing. If you do nothing this pull request will be closed eventually by the stale bot

[jj22ee]

Not stale.

[jj22ee]

Also requesting @lukeina2z for review.

[lukeina2z]

enable override.

Suggested change

	ENV['OTEL_TRACES_EXPORTER'] = 'console'
	ENV['OTEL_SERVICE_NAME'] = 'xray-sampler-on-rails-service'
	ENV['OTEL_TRACES_EXPORTER'] ||= 'console'
	ENV['OTEL_SERVICE_NAME'] ||= 'xray-sampler-on-rails-service'

[lukeina2z]

"trace_request_demonstration", typo?

[lukeina2z]

<= 0?